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2.5 Volume Commands

The following commands are available on the Geometry/Volume subpad.

Symbol Command Description
Form Volume Creates volumes from existing faces or edges
Create Volume Creates a volume in one of several primitive shapes
Boolean Operations Unites, intersects, or subtracts volumes
Blend Real Volumes Rounds and/or trims volume edges
Modify Volume Color
Modify Volume Label
Changes a volume color: changes a volume label
Move/Copy Volumes
Align Volumes
Moves and/or copies volumes; aligns volumes and connected geometry
Split Volume
Merge Volumes
Splits or merges volumes
Smooth/Heal Real Volumes
Convert Volumes (Nonreal to Real)
Smoothes and heals real volume geometry; converts non-real volumes to real volumes
Summarize Volumes
Check Volumes
Query Volumes
Total Entities
Displays volume summary information; checks validity of topology and geometry; opens a volume query list; displays entity totals
Delete Volumes Deletes real or virtual volumes


2.5.1 Form Volume

The Form Volume command button allows you to perform the following operations.

Symbol Operation Description
Stitch Faces Creates volumes from sets of existing faces
Sweep Faces Creates volumes by sweeping faces along a specified path
Revolve Faces Creates volumes by revolving a faces through a specified angle
Create Volume from Wireframe Creates a volume from a set of existing edges


Stitch Faces

The Stitch Faces operation (volume create stitch command) forms one or more volumes from sets of existing faces. To form a volume by means of the Stitch Faces command, you must specify the following information:

Specifying the Faces

To form a volume by means of the face-stitch operation, you must specify a set of faces that constitute the boundaries of a closed volume. The boundary edges on adjacent faces in the set must be coincident to within either a default, specified, or computed tolerance value (see "Employing Tolerant Modeling," below).

NOTE: GAMBIT allows you to stitch faces to create volumes that contain dangling faces and/or voids regardless of whether the volume to be created is real or virtual.

Automatically Stitching Connected Faces

When you specify a set of faces to create a single volume, GAMBIT automatically searches the model for any connected faces that can be used as boundaries of the volume to be created. Consequently, it is often not necessary to specify all of the faces in the set that defines the closed volume. For example, if you specify only one face in a set of three connected faces that can be used to define a cylinder, GAMBIT automatically adds the other two faces to the list of faces to be stitched in creating the cylindrical volume. (NOTE: This feature does not apply to the creation of multiple volumes (see, "Specifying the Number of Volumes," below).)

Employing Tolerant Modeling

If you specify a set of faces the boundary edges of which are exactly coin­cident (to within the GAMBIT default modeling tolerance of 10-6), GAMBIT constructs the volume by means of standard ACIS modeling operations. If the boundary edges are nearly coincident (that is, close to each other but not to within the default tolerance), GAMBIT employs "tolerant" modeling when creating the volume. In tolerant modeling, GAMBIT assigns individual toler­ances, as necessary, to edges and vertices so that the boundary edges of adjacent faces can be considered "coincident".

As an example of the use of tolerant modeling when stitching faces, consider the geometry shown in Figure 2-127(a). The geometry consists of three real faces that generally enclose a cylindrical volume. The tubular face (B) is connected to the lower end-cap face (A) by means of a common, circular edge; however, the upper end-cap face (C) is separated from the tubular face by a large gap.

Figure 2-127: Effect of tolerant modeling on face-stitch operations

If you stitch the three faces to create a real volume, GAMBIT automatically employs tolerant modeling to create the cylindrical volume shown in Figure 2-127(b). In this case, GAMBIT assigns a tolerance to the circular edge that bounds face C' such that faces B and C are considered "coincident".

Effect of Tolerant Modeling on Shading and Meshing

Shading and meshing operations can be greatly affected by the use of tolerant geometry. For example, when applying tolerant geometry to create the volume shown in Figure 2-127(b), above, GAMBIT does not relocate the surface associated with face C; it simply makes its boundary edge "coincident" with the upper edge of the tubular face. As a result, the shaded upper surface of the created volume is not coplanar with the boundary edge of its corresponding face (see Figure 2-128(a)).

Figure 2-128: Shading and meshing of tolerant geometry

The effect of tolerant modeling on meshing operations is similar to that for shading. For example, if you mesh the end-cap faces of the cylindrical volume shown in Figure 2-127(b), GAMBIT creates meshes such as those shown in Figure 2-128(b). In this case, the meshing of the upper face results in a jump between the mesh on its underlying surface and its boundary edge. It is advisable in such cases to specify a mesh interval size that is larger than the size of the original gap between the faces.

Specifying the Number of Volumes

The Number option on the Stitch Faces form allows you to specify the number of volumes to be created from the Stitch Faces operation. GAMBIT provides two Number options:

If you select the Single volume option, GAMBIT attempts to form a single volume from the specified faces. If you select the Multiple volumes option, and the specified faces can be grouped into two or more sets of connected faces each set of which bounds a separate, closed volume, GAMBIT forms multiple volumes from the operation.

NOTE: If you specify the Single volume option, GAMBIT automatically searches the model for any faces connected to the specified face(s) that can be used to form the closed volume (see "Automatically Stitching Connected Faces," above). If you specify the Multiple volumes option, GAMBIT does not automatically search for and include such faces.

Specifying the Volume Type

The Stitch Faces command can be used to form real and/or virtual volumes. To form a real volume, you must specify only real faces. To form a virtual volume, you can specify real and/or virtual faces. (NOTE: If you specify the Number:Multiple volumes option, GAMBIT creates real and/or virtual volumes where appropriate based on the types of the specified faces.)

Specifying the Tolerance Option

GAMBIT provides two Tolerance options for the face-stitch operation:

If you specify the Auto option, GAMBIT uses an internal algorithm to compute the tolerance used in the operation. If you specify the Manual option, you can specify a tolerance value by means of the Tolerance text box.

The purpose of the Tolerance option depends, in part, on whether the volume to be created is real or virtual.

Creating Real Volumes

If you specify the Auto option when creating a real volume, GAMBIT uses an internal algorithm to compute the tolerance. If the largest gap between "coincident" edges is greater than the computed tolerance, GAMBIT aborts the face-stitch operation and displays an error message in the Transcript window.

The Manual option allows you to force GAMBIT to apply tolerant modeling regardless of the size of the gap between edges to be made "coincident". The specified Tolerance value must be greater than the largest gap between edges to be made "coincident".

Creating Virtual Volumes

When creating virtual volumes, the Tolerance option allows you to specify the value used to determine whether the boundary edges of any two adjacent faces are close enough to be joined and connected by a virtual operation.

Using the Stitch Faces Form

To open the Stitch Faces form (see below), click the Stitch Faces command button on the Geometry/Volume subpad.

The Stitch Faces form includes the following specifications.

Faces specifies the faces to be used in forming the volume.
Number:
Single volume specifies the creation of a single volume.
Multiple volumes specifies the creation of multiple volumes.
Type:
Real specifies the creation of one or more real volumes.
Virtual specifies the creation of one or more virtual volumes.
Real and Virtual specifies the creation of real and/or virtual volumes where appropriate.
Tolerance specifies the tolerance value. GAMBIT provides two Tolerance options:
  • Auto
  • Manual
The purpose of the Tolerance option depends, in part, on the type of volume created by means of the face-stitch operation (see above).
Label specifies a label for the new volume. (See Section 2.1.1.)


Sweep Faces

The Sweep Faces operation (volume create translate and volume create rotate commands) creates volumes by sweeping real or non-real faces along a specified path. If you sweep a real face, GAMBIT creates a real volume. If you sweep a non-real face, GAMBIT creates a virtual volume.

The Sweep Faces operation requires the following input parameters.

The profile consists of a set of one or more faces to be swept. The path represents the trajectory of the sweep operation. The With mesh option determines whether GAMBIT creates a meshed volume when sweeping a meshed face. The type defines the shape and orienta­tion of the created volume relative to those of the profile and path.

Specifying the Sweep Profile

The sweep profile consists of a set of one or more existing faces. GAMBIT creates a sepa­rate volume corresponding to each face in the profile. Each type of sweep operation possesses its own set of rules that govern whether or not a face constitutes a valid profile component. In general, however, GAMBIT does not allow you to specify profile faces the normals of which are perpendicular to the sweep path.

Specifying the Sweep Path

You can define the sweep path by means of either of the following specifications.

When you describe the sweep path by specifying an edge, GAMBIT defines the path according to the shape, length, and sense of the specified edge. You can reverse the direction of the sweep path relative to the sense of the specified edge by means of the Reverse option on the Sweep Edges form.

When you define the sweep path by specifying a vector, GAMBIT defines the path as a straight line possessing the magnitude and direction of the vector. You must define the vector by means of the Vector Definition form (see "Using the Vector Definition Form" in Section 2.1.4).

Specifying the With mesh Option

If you sweep a meshed face, GAMBIT allows you to project the face mesh during the sweep operation, thereby creating a meshed volume. This option is invoked by means of the With mesh option on the Sweep Faces form. The created volume mesh is a Cooper mesh wherein the profile face serves as a source face for the Cooper operation. (For a description of Cooper meshing, see "Cooper Meshing Scheme," in Section 3.4.1 of this guide.)

If the sweep path is defined by a meshed edge, GAMBIT uses the mesh-node spacing on the path edge to determine the mesh-element spacing along the barrel of the Cooper logical cylinder. Other­wise, GAMBIT computes the mesh element spacing based on the value of the MESH.INTERVAL.SIZE default parameter.

As an example of the effect of the With mesh option, consider the path and profile shown in Figure 2-129(a). The profile consists of a square planar face aligned with the z-x plane, and the path is a circular arc edge aligned with the y-z plane. The profile face is meshed using a simple Map scheme, and the path edge is meshed using double-sided grading with the mesh nodes concentrated near its endpoints.

Figure 2-129: Effect of With mesh option on face-sweep operations

If you perform a simple rigid sweep operation using this path and profile and select the With mesh option, GAMBIT sweeps the profile along the path to create the meshed volume shown in Figure 2-129(b). In this case, the mesh density along the vertical sides of the volume is determined by the mesh node spacing on the path edge.

NOTE: In general, the With mesh option does not produce a meshed volume when using the Extended or Round perpendicular sweep-type options (see "The Effect of Draft Type," below).

Specifying the Sweep Type

GAMBIT provides two general types of sweep operations:

When you specify a rigid sweep, GAMBIT sweeps the profile along the entire length of the specified path without altering the profile orientation with respect to the global coordinate system. When you specify a perpendicular sweep, GAMBIT maintains a constant angle between the face normal and the sweep path along the entire length of the path.

Performing a Rigid Sweep

When you specify a rigid sweep operation, GAMBIT sweeps the profile along the specified path without altering the orientation of the profile with respect to the global coordinate system. The shape and orientation of a volume created by means of a rigid sweep operation depends on two factors:

Specifying the Profile

The edges that bound the profile face(s) can be straight or curved, and the profile face does not have to be planar. However, GAMBIT imposes the following restrictions on profiles and paths employed in face-sweep operations:

Figure 2-130 shows three path/profile configurations only one of which constitutes a valid configuration for a face-sweep opera­tion. (NOTE: The cubic volumes shown in Figure 2-130 are included for spatial reference only.)

Figure 2-130: Allowed face configurations for sweeping a face

The configuration shown in Figure 2-130(a) is not valid because edge AB is paral­lel to the path. The configuration shown in Figure 2-130(b) is not valid because the normal to the face (ABC) is perpen­dicu­lar to the path at its starting point (D). The configuration shown in Figure 2-130(c) is valid because none of its bounding edges is parallel to the path.

Specifying the Path

The sweep path can be defined by means of either an edge or a vector. If you specify an edge to define the path, the path can be straight or curved. If you specify a vector to define the path, the path is straight by definition.

Example Face-Sweep Operations

Figure 2-130 and Figure 2-131 illustrate the results of the rigid face-sweep operation for two simple path/profile configurations. In each case, the profile is a square planar face aligned with the z-x axis. The sweep paths shown in Figure 2-130 and Figure 2-131 are defined by straight and circular arc edges, respectively.

Figure 2-131: Example rigid face-sweep operation—straight path

Figure 2-132: Example rigid face-sweep operation—curved path

Performing a Perpendicular Sweep

Perpendicular sweep operations differ from rigid sweep opera­tions in that, for perpendicular sweeps, the initial orientation between the profile and path is main­tained along the entire length of the sweep path. Rigid sweeps, by contrast, maintain the orientation of the profile with respect to the global coor­dinate system along the sweep path.

As an example of the difference between rigid and perpendicular sweep oper­ations, consider the profile and path shown in Figure 2-132(a), above. Figure 2-133(a) and (b) show wireframe views of the volumes created by rigid and perpendicular sweep operations, respectively.

Figure 2-133: Example rigid and perpendicular sweep operations

When performing a rigid sweep, GAMBIT maintains the orientation of the profile with respect to the global coordinate system, thereby creating the volume shown in Figure 2-133(a). When performing a perpendicular sweep, GAMBIT maintains the orientation between the path and profile throughout the sweep and creates the volume shown in Figure 2-133(b). (NOTE: The volume shown in Figure 2-133(b) represents the results of a perpendicular sweep with a zero draft angle (see "The Effect of Draft Angle," below).)

The Effect of Path Position

The shape of the created volume depends, in part, on the relative positions of the profile and path and on whether or not the path starts at a point on the profile.

Path Starting on Profile

If the path edge starts on the profile, GAMBIT maintains the global pos­ition of the path when performing the sweep operation. In addition, GAMBIT uses the path edge itself as a boundary edge for the created volume.

As an example of this behavior, consider the perpendicular sweep operation illustrated in Figure 2-134. In this case, the profile consists of a square planar face that lies in the z-x plane, and the path is defined by a circular arc edge lies in the y-z plane (see Figure 2-134(a)). The path is connected to the profile at vertex a.

Figure 2-134: Perpendicular sweep—profile connected to path at vertex a

Because the path starts on the profile at vertex a, GAMBIT maintains the global position of the path when sweeping the face and employs the path edge itself as one boundary edge of the created volume (see Figure 2-134(b)).

The point at which the path starts on the profile strongly affects the shape of the created volume. For example, if the path shown in Figure 2-134(a), above, is connected to the profile at vertex b rather than vertex a (see Figure 2-135(a)), GAMBIT creates the volume shown in Figure 2-135(b).

Figure 2-135: Perpendicular sweep—profile connected to path at vertex b

Path Not Starting on Profile

If the path edge does not start on the profile, GAMBIT typically moves the starting point of the path to the nearest point on the profile when performing the sweep operation. (NOTE: The nature of the ACIS operations involved in the sweep operation makes it difficult to generalize the behavior when the path is not connected to the profile.)

Figure 2-136 shows a typical sweep operation for case in which the path does not start on the profile. In this case, GAMBIT moves the path to the nearest point on the profile when conducting the sweep operation. (NOTE: The sweep path is shown in Figure 2-136(b) for illustrative purposes only; GAMBIT does not actually create an edge at the location of the sweep path.)

Figure 2-136: Perpendicular sweep—profile not connected to path

The Effect of Sweep Method Default Variable

The shape of any volume created by means of the face-sweep operation can be affected, in part, by the value associated with the GEOMETRY.VOLUME.SWEEP_METHOD default variable. The SWEEP_METHOD default variable allows you to control the shape of the created volume at the end of the sweep path. If the profile is a planar face and you set the default variable equal to 2, GAMBIT constructs the volume such that one end represents the truncation of the sweep operation by a plane perpendicular to the path at its endpoint.

As an example of the effect of the SWEEP_METHOD default variable for a planar profile, consider the two volumes shown in Figure 2-137. Both volumes are created by sweeping the path/profile combination indicated in Figure 2-131(a), above. They differ only with respect to the value of the SWEEP_METHOD default variable.

Figure 2-137: Effect of SWEEP_METHOD default variable

When the SWEEP_METHOD default variable is specified as 0 or 1, GAMBIT maintains the original profile orientation throughout the sweep operation and creates the volume shown in Figure 2-137(a). When the SWEEP_METHOD default variable is specified as 2, GAMBIT truncates the volume at the end of the sweep operation by a plane perpendicular to the path at its endpoint Figure 2-137(b).

Perpendicular Sweep Methods

GAMBIT provides two options for perpendicular face-sweep operations:

The Draft option specifies a fixed angle of expansion or contraction for the profile as it is swept along the path. The Twist option allows you to revolve the profile through a specified angle as it is swept along the path.

NOTE (1): GAMBIT does not allow you to use the Draft or Twist options when sweeping a non-real face.
NOTE (2): In order to constitute a valid configuration for a Draft operation, the profile and path must meet the following conditions.
  • The profile must be planar.
  • The face normal must not be perpendicular to the path.

Draft Option

When you create a volume by means of the draft method, GAMBIT allows you to expand or contract the projected face by a specified angle along the path. Figure 2-138 shows the results of a perpendicular draft sweep opera­tion involving a profile and path identical to those shown in Figure 2-132(a). In this case the draft angle is specified as +10°; therefore, the profile expands as it is swept along the path.

Figure 2-138: Perpendicular face sweep—draft option, +10° draft angle

The Effect of Draft Angle

As noted above, when you perform a perpendicular face-sweep operation by means of the draft method, GAMBIT allows you to specify a draft angle for the created volume. The draft angle represents the extent to which the profile is expanded or contracted as it is swept along the path.

Figure 2-139 shows the effect of draft angle on the shape of a volume created by sweeping a square profile along a straight path oriented perpendicular to the face. In this case, the profile face is a square, planar face aligned with the z-x plane, the path is defined by a straight edge aligned with the y axis.

Figure 2-139(b), (c), and (d) shows the effects of specifying draft angles of 0°, +10°, and -10°, respectively. The positive draft angle expands the profile along the length of the path (Figure 2-139(c)); the negative draft angle contracts the profile along the length of the path (Figure 2-139(d)).

Figure 2-139: Perpendicular draft face sweep—effect of draft angle

The Effect of Draft Type

When you sweep a face by means of the perpendicular draft method and expand the profile by means of a positive draft angle, GAMBIT allows you to specify the following options for the expanded profile type:

Figure 2-140 shows the effect of draft type on the shape of a volume created from a profile and path identical to those shown in Figure 2-139(a) using a draft angle of +10°. The Extended option expands the profile with altering its basic shape (see Figure 2-140(a)). The Round option rounds the corners of the expanded profile as shown in Figure 2-140(b). (NOTE: The Mixed option combines elements of the Extended and Round options, as necessary, to fill gaps in the expanded profile.)

Figure 2-140: Perpendicular face sweep, draft method—effect of draft type

Twist Method

When you perform a perpendicular sweep operation by means of the twist method, GAMBIT revolves the profile through a specified angle along the length of the path. The profile and path can be straight or curved.

As an example of the effects of the twist method, consider the profile/path configuration shown in Figure 2-141(a). In this case, the profile consists of a square planar face aligned with the z-x plane, and the path is defined by a circular arc edge aligned with the y-z plane. If you sweep the profile shown in Figure 2-141(a) and specify a twist angle of +180°, GAMBIT creates the volume shown in Figure 2-141(b).

Figure 2-141: Twist-method face-sweep operation, 180° twist angle

By default, GAMBIT moves the path (twist axis) to the nearest point on the profile face before sweeping the face to create the volume. Consequently, one bounding edge of the volume possesses a shape and orientation identical to that of the sweep path. You can control the location of the sweep path during a face-sweep operation by means of the GEOMETRY.VOLUME.SWEEP_PATH_ALIGNMENT default variable, which determines whether or not GAMBIT moves the sweep path prior to sweeping the face. By default, GAMBIT moves the sweep path (SWEEP_PATH_ALIGNMENT = 1), thereby performing operations such as that illustrated in Figure 2-141. If you specify the SWEEP_PATH_ALIGNMENT default variable as 0, GAMBIT maintains the global position and orientation of the path when sweeping the profile, thereby performing operations such as that shown in Figure 2-142.

Figure 2-142: Twist-method face sweep—SWEEP_PATH_ALIGNMENT = 0

Using the Sweep Faces Form

To open the Sweep Faces form (see below), click the Sweep Faces command button on the Geometry/Volume subpad.

The Sweep Faces form includes the following specifications.

Faces specifies one or more faces that constitute the sweep profile.
Path:
Edge specifies that the path is described by the length, orientation, and sense of an existing edge.
Edge specifies the edge to be used as the sweep path.
Reverse specifies that the direction of the path is reversed with respect to the sense of the specified edge.
Vector specifies that the path is described by a vector.

When you select the Vector option, GAMBIT displays a command button titled Define Vector. When you click the Define Vector command button, GAMBIT opens the Vector Definition form, which allows you to specify parameters that define the path vector. For instructions on using the Vector Definition form, see "Using the Vector Definition Form" in Section 2.1.4.

With mesh (Meshed profile faces only) projects the face mesh when sweeping the face(s), thereby creating a set of meshed volumes.
Type:
Rigid specifies a rigid sweep operation.
Perpendicular specifies a perpendicular sweep operation.
Option:
Draft specifies the perpendicular draft method.
Twist specifies the perpendicular twist method.
Angle specifies the draft or twist angle.
Type:
Extended specifies that an expanded profile projection reflects the basic shape of the profile.
Round specifies that an expanded profile projection is to contain rounded edges.
Mixed employs elements of the Extended and Round options to fill gaps in the expanded profile.
Label specifies a label for one of the new volumes (see Section 2.1.1).


Revolve Faces

The Revolve Faces operation (volume create revolve command) forms a set of volumes by revolv­ing one or more faces through a specified angle. The operation requires specification of the following parameters:

The axis of revolution does not have to be coincident with one of the edges of the face to be swept, but it must lie in the same plane as the profile face (see Figure 2-143).

Figure 2-143: Face revolve parameters

Specifying Faces to Be Revolved

To create a volume by means of the Revolve Faces form, you must specify one or more faces to be revolved about the axis of rotation. Each specified face can include any combination of straight and curved edges as long as all the edges comprising the face lie in a single plane.

Specifying the Axis of Revolution

In order to constitute a valid axis of revolution for the face-revolve operation, the axis must lie in the plane of the face. To specify the axis of revolution, you must define the axis by means of the Vector Definition form. For a description of the Vector Definition form and its operation, see "Using the Vector Definition Form" in Section 2.1.4. The conventions regarding the angle of revolution for the Revolve Faces operation are identical to those described in "Rotating an Entity" in Section 2.1.4.

Specifying the Angle of Revolution

The angle of revolution is defined according to the right-hand rule relative to the direction of the axis vector. That is, when the axis of revolution is oriented such that its vector points away from the observer, angles swept in the clockwise direction are defined as positive (see Figure 2-137, above).

Specifying Draft Angle and Type

When you create a volume by revolving a face, GAMBIT allows you to specify a draft angle and type to be applied in conjunction with the revolution of the face. The draft angle represents the extent to which the profile is expanded or contracted as the face is revolved. The draft type determines whether or not the edges of an expanded profile are rounded in the process of creating the volume.

Figure 2-144 shows two volumes created by revolving a rectangular face and specifying a positive draft angle—that is, an expansion of the profile. In Figure 2-144(a), the draft type is extended, therefore the basic shape of the face does not change as it is revolved. In Figure 2-144(b), the draft type is round, therefore the corners of the revolved face are rounded with respect to the original profile.

Figure 2-144: Revolving faces—effect of draft angle and type

Specifying the With mesh Option

When you revolve a meshed face to create a volume, GAMBIT allows you to project the face mesh during the face-revolve operation, thereby creating a meshed volume. The created volume mesh is a Cooper mesh wherein the sweep-profile face serves as a source face for the Cooper operation. (For a description of Cooper meshing, see "Cooper Meshing Scheme," in Section 3.4.1 of this guide.) GAMBIT computes the mesh element spacing along the Cooper "barrel" face(s) based on the value of the MESH.INTERVAL.SIZE default parameter.

To project the mesh of a profile face when revolving the face, select the With mesh option on the Revolve Faces form.

Using the Revolve Faces Form

To open the Revolve Faces form (see below), click the Revolve Faces command button on the Geometry/Volume subpad.

The Revolve Faces form includes the following specifications.

Faces specifies one or more faces to be revolved.
Angle specifies the angle (in degrees) through which the face is to be revolved.
Axis: contains two components:
  • A Define command button that allows you to define the axis around which the edge is to be revolved
  • The coordinates of the start and end points for a vector defining the rotational axis
Draft:
Extended specifies expanding or contracting the profile face as it is revolved according to the specified draft angle.
Round specifies that the corners of an expanded profile are rounded.
Angle specifies the draft angle.
With mesh (Meshed profile faces only) projects the face mesh when revolving the face(s), thereby creating a set of meshed volumes.
Label specifies a label for one of the new volumes (see Section 2.1.1).


Create Volume from Wireframe

The Create Volume from Wireframe operation (volume create wireframe command) creates a real or virtual volume from a set of existing edges. The command requires the following specifications.

Specifying the Edges

To create a volume by means of the Create Volume from Wireframe operation, you must specify a set of edges that define the shape of the volume. GAMBIT imposes the following restrictions on any set of edges used for the operation.

Figure 2-145 illustrates the effects of the rules outlined above as they apply to four example sets of edges, only one of which consti­tutes a valid wireframe for the Create Volume from Wireframe operation.

Figure 2-145: Valid and invalid wireframe configurations

The edge sets shown the figure are valid or invalid for the following reasons.

Configuration Valid/Invalid Reason
(a) Valid All of the edges possess at least one endpoint vertex that is coincident with that of at least one other edge, and none of the edges are wholly internal to the cube.
(b) Invalid The circular edges of the cylindrical region cannot be connected to the boundaries of the cube by means of existing edges.
(c) Invalid Four of the edges in the set cannot be joined to the edges of the cube.
(d) Invalid The edges of the pyramidal region exist entirely within the volume represented by the edges of the cube.

If GAMBIT cannot resolve the specified set of edges into a valid volume, it executes as much as the creation process as is possible—including the crea­tion of faces—and displays a warning in the Transcript window.

Specifying the Geometry Type

The Create Volume from Wireframe operation can be used to create either real or virtual volumes. If you specify the creation of a virtual volume, you must also specify a Tolerance value. The Tolerance value defines the maxi­mum allowable tolerance between endpoint vertices that are to be considered "coincident" when attempting to construct the volume.

GAMBIT provides two Tolerance options:

Using the Create Volume from Wireframe Form

To open the Create Volume from Wireframe form (see below), click the Create Volume from Wireframe command button on the Geometry/ Volume subpad.

The Create Volume from Wireframe form includes the following specifications.

Edges specifies the edges that define the shape of the volume.
Type: specifies the geometry type for the created volume:
  • Real—creates a real volume
  • Virtual—creates a virtual volume
Tolerance (Virtual option only) specifies the tolerance value used to determine whether edge endpoint vertices are "coincident":
  • Auto—uses the GAMBIT default tolerance (10-5)
  • Manual—allows you to specify a tolerance value
Label specifies a label for the new volume. (See Section 2.1.1.)


2.5.2 Create Volume

The Create Volume command button allows you to perform the following operations.

Symbol Operation Description
Create Real Brick Creates a volume in the shape of a rectangular brick
Create Real Cylinder Creates a volume in the shape of a cylinder
Create Real Prism Creates a volume in the shape of a regular prism
Create Real Pyramid Creates a volume in the shape of a truncated pyramid
Create Real Frustum Creates a volume in the shape of a frustum
Create Real Sphere Creates a volume in the shape of a sphere
Create Real Torus Creates a volume in the shape of a torus


Create Real Brick

The Create Real Brick operation (volume create brick command) creates a volume in the shape of a rectangular brick. To perform the operation, you must specify the following parameters:

Specifying the Dimensions

When you create a rectangular brick volume by means of the Create Real Brick option, GAMBIT applies the width, depth, and height specifications to the x, y, and z directions, respectively. To define the locations of the brick edges relative the origin of the reference coordinate system, you must specify the position of the brick (see below).

Specifying the Position of the Brick

To orient the brick relative to the reference coordinate system, you must specify the directions in which to apply the dimensions of the edges—that is, whether GAMBIT applies the width, depth, and height dimension parameters in the positive or negative direction with respect to each of the coordinate axes. The nine allowable direction options are as follows:

Figure 2-146 shows the effect of four different direction options on the position of a cube created by means of the Create Real Brick form.

Figure 2-146: Effect of direction option on brick position

Using the Create Real Brick Form

To open the Create Real Brick form (see below), click the Create Real Brick command button on the Geometry/Volume subpad.

The Create Real Brick form includes the following specifications.

Width specifies the dimension of the brick in the x direction.
Depth specifies the dimension of the brick in the y direction.
Height specifies the dimension of the brick in the z direction.
Coordinate Sys. specifies the reference coordinate system.
Direction
+X +Y +Z
+X +Y -Z
+X -Y +Z
+X -Y -Z
-X +Y +Z
-X +Y -Z
-X -Y +Z
-X -Y -Z
Centered
specifies the direction of each brick dimension relative to the reference coordinate system. The X, Y, and Z directions correspond to the brick Width, Depth, and Height parameters, respectively. The centered option specifies that the center of the brick coincides with the origin of the reference coordinate system.
Label specifies a label for the new volume. (See Section 2.1.1.)


Create Real Cylinder

The Create Real Cylinder operation (volume create frustum command) creates a circular or elliptical cylinder possessing a constant cross-sectional area. To perform the operation, you must specify the following parameters:

Specifying the Cylinder Height

The height of the cylinder represents length of the cylinder along its axis. By default, the cylinder axis coincides with the z axis of the reference coordinate system. To change the orientation of the cylinder, you must specify the axis location (see below).

Specifying the Cylinder Radii

To define the cross section of the cylinder, you must specify its major and minor axes. To do so, you must specify two radii—Radius 1 and Radius 2—each of which is aligned with a coordinate axis. Either radius can constitute the major axis of the cylinder cross section. If you do not specify Radius 2, GAMBIT creates a circular cylinder of radius Radius 1.

By default, Radius 1 is aligned with the x axis, and Radius 2 is aligned with the y axis. If you change the orientation of the cylinder by specifying the axis location (see below), the axes corresponding to Radius 1 and Radius 2 change as well. The following table summarizes the relationship between axis location, Radius 1, and Radius 2.

Axis Location Radius 1 Axis Radius 2 Axis
z x y
y z x
x y z

Specifying the Axis Location

To locate and orient the cylinder, you must specify its axis location relative to the reference coordinate system. The axis location specification includes a coordinate axis and a direction. There are nine possible options for the axis location, each of which represents a different combination of three directions (positive, centered, and negative) and three coordinate axes (x, y, and z). The default axis location is Positive Z.

Figure 2-147 shows the effects of four different axis locations on the position of an elliptical cylinder created by means of the Create Real Cylinder form. In this example, the cylinder Height, Radius 1, and Radius 2 specifications are 7, 3, and 2, respectively.

Figure 2-147: Effect of axis location on cylinder position and orientation

Using the Create Real Cylinder Form

To open the Create Real Cylinder form (see below), click the Create Real Cylinder command button on the Geometry/Volume subpad.

The Create Real Cylinder form includes the following specifications.

Height specifies the length of the cylinder in the direction of its specified axis.
Radius 1 specifies one of two radii defining the cross section of the cylinder.
Radius 2 specifies the other of two radii defining the cross section of the cylinder.
Coordinate Sys. specifies the reference coordinate system.
Axis Location
Positive Z
Centered Z
Negative Z
Positive X
Centered X
Negative X
Positive Y
Centered Y
Negative Y
specifies the cylinder axis and the direction in which the cylinder is created relative to the axis. There are three possible options for each axis:
  • Positive—applies the Height dimension in the positive axis direction relative to the origin of the reference coordinate system
  • Centered—centers the cylinder at the origin of the reference coordinate system
  • Negative—applies the Height dimension in the negative axis direction relative to the origin of the reference coordinate system
Label specifies a label for the new volume. (See Section 2.1.1.)


Create Real Prism

The Create Real Prism operation (volume create pyramid command) creates a regular prism possessing a constant cross-sectional area. Each side of the prism is parallel to the prism axis. To perform the operation, you must specify the following parameters:

Specifying the Prism Height

The height of the prism represents length of the prism along its axis—that is, perpendicular to its cross section. By default, the prism axis coincides with the z axis of the reference coordinate system. To change the orientation of the prism, you must specify the axis location (see below).

Specifying the Number of Prism Sides

To create a prism, you must specify the number of its sides (n = 3). GAMBIT constructs the prism such that each side is parallel to the prism axis.

The positions of the prism sides depend, in part, on whether you specify an odd number or even number of sides. If you specify an odd number of sides, GAMBIT constructs the prism such that one of its corner vertices lies within a coordinate plane of the reference coordinate system. If you specify an even number of vertices, GAMBIT constructs the prism such that one of its sides is parallel to a coordinate plane of the reference system.

Figure 2-148 shows the cross sections (in the x-y plane) of four prisms, each of which is circumscribed by a circular cylinder. In Figure 2-148(a), each prism possesses an odd number of sides. In Figure 2-148(b), each prism possesses an even number of sides. Note the following characteristics:

Figure 2-148: Effect of the number of prism sides

Specifying the Prism Radii

To define the dimensions of the prism, you must specify the major and minor axes of an ellipse by which its cross section is circumscribed. To do so, you must specify two radii—Radius 1 and Radius 2—each of which is aligned with a coordinate axis. Either radius can constitute the major axis of the ellipse. If you do not specify Radius 2, GAMBIT circumscribes the prism by a circular cylinder of radius Radius 1.

By default, Radius 1 is aligned with the x axis, and Radius 2 is aligned with the y axis. If you change the orientation of the cylinder by specifying the axis location (see below), the axes corresponding to Radius 1 and Radius 2 change, as well. The following table summarizes the relationship between axis location, Radius 1, and Radius 2 with respect to the corresponding coordinate axes.

Axis Location Radius 1 Axis Radius 2 Axis
z x y
y z x
x y z

The Effect of Radii Specifications

If you specify values for Radius 1 and Radius 2 that are identical to each other (or do not specify a value for Radius 2) GAMBIT creates a prism the cross section of which is circumscribed by a circle (see Figure 2-148, above). If you specify values for Radius 1 and Radius 2 that differ from each other, GAMBIT creates a prism the cross section of which is circumscribed by an ellipse.

The procedure by which GAMBIT creates a prism circumscribed by an ellipse can be thought of as a two-step process:

  1. Construct a prism circumscribed by a circular cylinder the radius of which is equal to the minor axis of the ellipse
  2. Reposition the corner vertices of the cross section along lines parallel to the major axis of the ellipse
Figure 2-149 shows the effect of specifying an elliptical boundary on the cross section of a five-sided prism oriented with an axis location in the Positive Z direction. In Figure 2-149(a), Radius 1 constitutes the major axis of the ellipse, therefore GAMBIT locates the corner vertices of the cross section along lines parallel to its corresponding axis—that is, the x axis. In Figure 2-149(b), Radius 2 constitutes the major axis, therefore GAMBIT locates the corner vertices along lines parallel to the y axis.

Figure 2-149: Effect of radii on prism cross section

Specifying the Axis Location

To locate the prism in the model domain, you must specify its axis location relative to the reference coordinate system. The axis location specification includes a coordinate axis and a direction. For a description of the axis location specification, see "Create Real Cylinder," above.

Using the Create Real Prism Form

To open the Create Real Prism form (see below), click the Create Real Prism command button on the Geometry/Volume subpad.

The Create Real Prism form includes the following specifications.

Height specifies the height of the prism.
Sides specifies the number of sides (n=3) of the prism.
Radius 1 specifies one of two radii that describe the ellipse that circumscribes the prism.
Radius 2 specifies the other of two radii that describe the ellipse that circumscribes the prism.
Coordinate Sys. specifies the reference coordinate system.
Axis Location
Positive Z
Centered Z
Negative Z
Positive X
Centered X
Negative X
Positive Y
Centered Y
Negative Y
specifies the axis of the prism and the direction in which the prism is created relative to the axis. There are three possible options for each axis:
  • Positive—applies the Height dimension in the positive axis direction relative to the origin of the reference coordinate system
  • Centered—centers the prism at the origin of the reference coordinate system
  • Negative—applies the Height dimension in the negative axis direction relative to the origin of the reference coordinate system
Label specifies a label for the new volume. (See Section 2.1.1.)


Create Real Pyramid

The Create Real Pyramid operation (volume create pyramid command) creates a volume in the shape of a pyramid—that is, a prism possessing a non-constant cross-sectional area. To perform the operation, you must specify the following parameters:

Specifying the General Pyramid Parameters

Four of the seven parameters required to specify a pyramid are identical to those required to specify a prism. The identical parameters are as follows:

For a description of how to specify these parameters, see "Create Real Prism," above.

Specifying the Pyramid Radii

When you create a pyramid by means of the Create Real Pyramid form, GAMBIT constructs a volume in the shape of a prism the base and top of which differ only in size. To define size and shape of the base and top, you must specify three radii—Radius 1, Radius 2, and Radius 3.

Radius 1 and Radius 2 constitute the axes of an ellipse that circumscribes the base of the pyramid. They are specified according to the same procedure used to specify the radii of a prism (see "Create Real Prism," above). Radius 3 specifies the size of the top of the pyramid relative to Radius 1.

Figure 2-150 shows a three-sided prism with an elliptical base defined by Radius 1 (minor axis) and Radius 2 (major axis). The top of the pyramid is identical in shape to the pyramid base, but the sizes of its edges differ from those of the base by the ratio Radius 3:Radius 1.

Figure 2-150: Pyramid radii specifications

Using the Create Real Pyramid Form

To open the Create Real Pyramid form (see below), click the Create Real Pyramid command button on the Geometry/Volume subpad.

The Create Real Pyramid form includes the following specifications.

Height specifies the height of the pyramid.
Sides specifies the number of sides (n=3) of the pyramid.
Radius 1 specifies one of two radii that define the major and minor axes of the ellipse that circumscribes the pyramid base.
Radius 2 specifies the other radius of the ellipse that circumscribes the pyramid base.
Radius 3 specifies the radius that defines the size of the top of the pyramid relative to the size of its base. (NOTE: The defining ratio is Radius 3: Radius 1.)
Coordinate Sys. specifies the reference coordinate system.
Axis Location
Positive Z
Centered Z
Negative Z
Positive X
Centered X
Negative X
Positive Y
Centered Y
Negative Y
specifies the axis of the pyramid and the direction in which the pyramid is created relative to the axis. There are three possible options for each axis:
  • Positive—applies the Height dimension in the positive axis direction relative to the origin of the reference coordinate system
  • Centered—centers the pyramid at the origin of the reference coordinate system
  • Negative—applies the Height dimension in the negative axis direction relative to the origin of the reference coordinate system
Label specifies a label for the new volume. (See Section 2.1.1.)


Create Real Frustum

The Create Real Frustum operation (volume create frustum command) creates a volume in the shape of a frustum—that is, a cylinder of non-constant cross-sectional area. To perform the operation, you must specify the following parameters:

Specifying the General Frustum Parameters

Three of the six parameters required to specify a frustum are identical to those required to specify a cylinder. The identical parameters include the following:

For a description of how to specify these parameters, see "Create Real Cylinder," above.

Specifying the Frustum Radii

When you create a frustum by means of the Create Real Frustum form, GAMBIT constructs a cylindrical volume the base and top of which differ only in size. To define the size and shape of the base and top, you must specify three radii-Radius 1, Radius 2, and Radius 3.

Radius 1 and Radius 2 are the axes of the ellipse that constitutes the base of the frustum. Radius 3 specifies the size of the top of the frustum relative to Radius 1.

Figure 2-151 shows a frustum with an elliptical base defined by Radius 1 (minor axis) and Radius 2 (major axis). The top of the frustum is identical in shape and orientation to the base, but the lengths of its axes differ from those of the base by the ratio of Radius 3:Radius 1.

Figure 2-151: Frustum radii specifications

Using the Create Real Frustum Form

To open the Create Real Frustum form (see below), click the Create Real Frustum command button on the Geometry/Volume subpad.

The Create Real Frustum form includes the following specifications.

Height specifies the height of the frustum.
Radius 1 specifies one of two radii that define of the ellipse that constitutes the frustum base.
Radius 2 specifies the other radius of the ellipse that constitutes the frustum base.
Radius 3 specifies the radius that defines the size of the frustum top relative to the size of its base. (NOTE: The defining ratio is Radius 3:Radius 1.)
Coordinate Sys. specifies the reference coordinate system.
Axis Location
Positive Z
Centered Z
Negative Z
Positive X
Centered X
Negative X
Positive Y
Centered Y
Negative Y
specifies the axis of the frustum and the direction in which the frustum is created relative to the axis. There are three possible options for each axis:
  • Positive—applies the Height dimension in the positive axis direction relative to the origin of the reference coordinate system
  • Centered—centers the frustum at the origin of the reference coordinate system
  • Negative--applies the Height dimension in the negative axis direction relative to the origin of the reference coordinate system
Label specifies a label for the new volume. (See Section 2.1.1.)


Create Real Sphere

The Create Real Sphere operation (volume create sphere command) creates a volume in the shape of a sphere. To perform the operation, you must specify the radius of the sphere and the coordinate system the origin of which constitutes the center of the sphere.

Using the Create Real Sphere Form

To open the Create Real Sphere form (see below), click the Create Real Sphere command button on the Geometry/Volume subpad.

The Create Real Sphere form includes the following specifications.

Radius specifies the radius of the sphere.
Coordinate Sys. specifies the coordinate system the origin of which constitutes the center of the sphere.
Label specifies a label for the new volume. (See Section 2.1.1.)


Create Real Torus

The Create Real Torus operation (volume create torus command) creates a volume in the shape of a torus. To perform the operation, you must specify the following parameters:

Specifying the Radii of the Torus

To define the dimensions of a torus, you must specify two radii (see Figure 2-152). The circumferential radius (Radius 1) defines the size of the circle that constitutes the center of the torus tube. The tube radius (Radius 2) defines the size of the tube itself.

Figure 2-152: Torus radius specifications

Specifying the Axis of the Torus

To orient the torus in the model domain, you must specify the coordinate axis that constitutes the central axis of the torus. The axis options include X axis, Y axis, and Z axis.

Using the Create Real Torus Form

To open the Create Real Torus form (see below), click the Create Real Torus command button on the Geometry/Volume subpad.

The Create Real Torus form includes the following specifications.

Radius 1 specifies the circumferential radius of the torus with respect to its center axis.
Radius 2 specifies the radius that defines the size of the torus tube.
Coordinate Sys. specifies the coordinate system that constitutes the center of the torus.
Center Axis
Z axis
X axis
Y axis
specifies the coordinate axis that constitutes the torus center axis.
Label specifies a label for the new volume. (See Section 2.1.1.)


2.5.3 Boolean Operations

The Boolean Operations command button allows you to perform the following operations.

Symbol Operation Description
Unite Real Volumes Unites two or more real volumes into one real volume
Subtract Real Volumes Subtracts the intersecting region(s) between two or more volumes
Intersect Real Volumes Creates a volume representing the intersection between two or more volumes


Overview

Each of the commands listed above allows you to perform a Boolean operation involving two or more intersecting volumes. Figure 2-153 illustrates the results of each of the Boolean volume operations on an intersecting cube and sphere.

Figure 2-153: Boolean volume operations

NOTE (1): Geometry that fails GAMBIT geometry checks ("bad" geometry) can sometimes cause Boolean operations to fail. By default, if a Boolean operation fails due to bad geometry, GAMBIT aborts the operation. It is possible, however, to specify that instead of aborting the procedure, GAMBIT automatically attempts to smooth and/or heal the geometry and retries the Boolean operation. This specification is made by means of the GEOMETRY.VOLUME.BOOLEAN_METHOD default variable. Specifically, if you set the GEOMETRY.VOLUME.BOOLEAN_METHOD default variable to 2, GAMBIT performs the automatic smooth/heal-retry operation.
NOTE (2): If you set the GEOMETRY.VOLUME.BOOLEAN_METHOD default variable to 3, GAMBIT attempts to preserve existing vertex, edge, and face labels when performing a volume Boolean operation.

Retaining the Specified Volumes

Each volume Boolean operation form includes at least one Retain option. When you perform a Boolean operation involving a set of specified volumes, GAMBIT replaces the specified volumes with a single volume that constitutes the result of the operation. If you select the Retain option, GAMBIT retains the original volumes when it performs the Boolean operation.


Unite Real Volumes

The Unite Real Volumes operation (volume unite command) unites two or more intersecting volumes into a single volume.

Specifying the Tolerance Value

GAMBIT allows you to specify the maximum allowable distance (tolerance) between volumes to be united. The operation includes two tolerance options:

If you specify the Auto option, GAMBIT automatically computes the tolerance based on an internal algorithm. If you specify the Manual option, GAMBIT allows you to specify a tolerance value (default = 10-6).

Using the Unite Real Volumes Form

To open the Unite Real Volumes form (see below), click the Unite command button on the Geometry/Volume subpad.

The Unite Real Volumes form includes the following specifications.

Volumes specifies the set of volumes to be united.
Retain specifies that the original volumes are retained.
Tolerance specifies the the maximum allowable distance between the volumes to be united.
  • Auto—Specifies that GAMBIT computes the tolerance value
  • Manual—Allows you to specify a tolerance value (default = 10-6)


Subtract Real Volumes

The Subtract Real Volumes operation (volume subtract command) performs a Boolean subtraction of one or more volumes from a single target volume.

Specifying the Tolerance Value

GAMBIT allows you to specify the maximum allowable distance (tolerance) between volumes to be subtracted. The operation includes two tolerance options:

If you specify the Auto option, GAMBIT automatically computes the tolerance based on an internal algorithm. If you specify the Manual option, GAMBIT allows you to specify a tolerance value (default = 10-6).

Using the Subtract Real Volumes Form

To open the Subtract Real Volumes form (see below), click the Subtract command button on the Geometry/Volume subpad.

The Subtract Real Volumes form includes the following specifications.

Volume specifies the target volume from which the intersecting region is subtracted.
Retain specifies that the target volume is retained.
Subtract
Volumes specifies one or more volumes that constitute the subtraction tools.
Retain specifies that all subtraction-tool volumes are retained.
Tolerance specifies the the maximum allowable distance between the volumes to be subtracted.
  • Auto—Specifies that GAMBIT computes the tolerance value
  • Manual—Allows you to specify a tolerance value (default = 10-6)


Intersect Real Volumes

The Intersect Real Volumes operation (volume intersect command) performs a Boolean intersection of two or more real volumes.

Specifying the Tolerance Value

GAMBIT allows you to specify the maximum allowable distance (tolerance) between volumes to be intersected. The operation includes two tolerance options:

If you specify the Auto option, GAMBIT automatically computes the tolerance based on an internal algorithm. If you specify the Manual option, GAMBIT allows you to specify a tolerance value (default = 10-6).

Using the Intersect Real Volumes Form

To open the Intersect Real Volumes form (see below), click the Intersect command button on the Geometry/Volume subpad.

The Intersect Real Volumes form includes the following specifications.

Volumes specifies two or more volumes for the intersection operation.
Retain specifies that all original specified volumes are retained.
Tolerance specifies the the maximum allowable distance between the volumes to be intersected.
  • Auto—Specifies that GAMBIT computes the tolerance value
  • Manual—Allows you to specify a tolerance value (default = 10-6)


2.5.4 Blend Real Volumes

The Blend Real Volumes operation (volume blend, edge chamfer, edge round, and vertex blend commands) rounds or chamfers (bevels) the edges of one or more real volumes. To perform the operation, you must specify the following parameters:

Each blend procedure specification consists of an edge or vertex and an associated blend type. When you click the Apply command button on the Blend Real Volumes form, GAMBIT executes all of the blend procedure specifications that are currently defined throughout the model.

Specifying Edge Blend Type

GAMBIT provides three types of edge blend procedures:

Figure 2-154 illustrates the basic shape of each type of edge blend procedure as performed on a single edge of a cube.

Figure 2-154: Edge blend types

The following sections describe the basic specifications and operations of the blend procedure types listed above.

Constant-Radius Round Edge Blend Procedure

To define a constant-radius round edge blend procedure, you must specify the following parameters:

When you perform the blend operation, GAMBIT replaces the specified edge with a curved face (see Figure 2-155). The shape of the face represents a surface formed by a ball of the specified radius rolling between the two faces that share the edge and touching them only at the two curves of tangency.

Figure 2-155: Constant-radius round edge blend specifications

Variable-Radius Round Edge Blend Procedure

To define a variable-radius round edge blend procedure, you must specify the following parameters:

When you perform the blend operation, GAMBIT replaces the specified edge with a rounded face the radius of which varies linearly along the length of the edge. The start and end radii specifications define the radius of the blend at the start and end endpoints of the edge, respectively (see Figure 2-156).

Figure 2-156: Variable-radius round edge blend specifications

Constant-Chamfer Edge Blend Procedure

To define a constant-chamfer edge blend procedure, you must specify the following parameters:

When you perform the blend operation, GAMBIT replaces the specified edge with a face the size and position of which is determined by the left and right range values as shown in Figure 2-157.

Figure 2-157: Constant-chamfer edge blend specifications

Specifying Multiple Edge Blend Procedures

When you perform a blend operation, GAMBIT applies all currently specified blend procedures to the model. If you specify blend procedures for more than one edge before performing the blend operation, GAMBIT applies the appropriate specifications to each edge.

If you specify edge blend procedures for two or more edges that are connected to each other, GAMBIT creates curves and faces where appropriate to represent the intersection of the blended edges. The types of edges and faces created at the intersection depend on both the individual edge blend specifications and the sequence in which the blend operations are performed.

The Effect of Edge Blend Specifications

As an example of the effect of blend specifications on the configuration of blended edges, consider the cubic volume shown in Figure 2-158.

Figure 2-158: Edge blend configurations

Figure 2-158(b), (c), (d), (e), and (f) illustrate the effect of edge blend procedure definitions on the blending of Edges 1 and 2 in Figure 2-158(a). The definitions corresponding to each figure are as follows.

Figure Edge Blend Procedure Definitions
(a) Original cube-no blended edges
(b) Edge 1: Constant-radius round blend
Edge 2: Constant-radius round blend
Radius 1 = Radius 2
(c) Edge 1: Constant-radius round blend
Edge 2: Constant-radius round blend
Radius 1 < Radius 2
(d) Edge 1: Constant-radius round blend
Edge 2: Variable-radius round blend
(e) Edge 1: Constant-chamfer blend
Edge 2: Constant-chamfer blend
Left and right range values identical for both edges
(f) Edge 1: Constant-radius round blend
Edge 2: Constant-chamfer blend

The Effect of Operation Sequence

When you apply blend procedures to three or more edges that intersect at a single vertex, the final shape of the blended edges depends, in part, on the sequence in which the blend operations are carried out. For example, Figure 2-159 illustrates the effect of blend operation sequence on the two-step blending of Edges 1, 2, and 3 in Figure 2-158(a).

Figure 2-159: The effect of edge blend operation sequence

The following table summarizes the blend operation sequences illustrated in Figure 2-159.

Figure Edge Blend Operation Sequence
(a) Step 1: Blend Edges 1 and 2
Radius 1 = Radius 2

Step 2: Blend Edge 3
Radius 3 > Radius 1

(b) Step 1: Blend Edge 3 (NOTE: When you blend Edge 3, GAMBIT creates Edge 4.)

Step 2: Blend Edges 1, 4, and 2
Radius 1 = Radius 4 = Radius 2 < Radius 3

Note that the procedures illustrated in Figure 2-159(a) and (b) are similar in that Edge 3 is blended by itself, and edges 1 and 2 are blended in tandem. The difference in the final configurations is due to the sequence in which the blend operations are carried out.

Specifying Vertex Blend Type

If you specify blend procedures for three or more edges that intersect at a common vertex, you can also specify a vertex blend procedure. When you perform a vertex blend operation, GAMBIT replaces the specified vertex with a face, each edge of which is connected to its neighbor.

To completely define a vertex blend procedure, you must specify the following parameters:

Bulge Parameter

The bulge parameter determines the degree to which the face created at the vertex is bowed. Its allowable values range from 0 (slightly bowed) to 2 (highly bowed). (NOTE: The default value for the bulge parameter is 1.)

NOTE: The bulge parameter affects only the shape of the surface of the face created at the blend vertex, not the position or orientation of its bounding edges. As a result, the bulge parameter does not affect the appearance of the wireframe view of the volume. To view the effect of the bulge parameter on the resulting face shape, you must display a shaded view of the volume. (See the GAMBIT User's Guide, Chapter 3.)

Setback Parameter

The setback parameter determines the distance by which the associated edge-blend faces are offset from the initial vertex location (see Figure 2-160).

Figure 2-160: The effect of setback specifications

You can specify setback values either for the vertex itself, or for each individual edge that intersects at the vertex. The edge and vertex setback specifications interact according to the following rules:

Using the Blend Real Volumes Form

To open the Blend Real Volumes form (see below), click the Blend command button on the Geometry/Volume subpad.

The Blend Real Volumes form includes the following specifications.

Volumes specifies the volume containing the edges and vertices to be blended.
Define Blend Types:
Edge opens the Edge Blend Type form, which allows you to define edge blend procedures (see "Using the Edge Blend Type Form," below).
Vertex opens the Vertex Blend Type form, which allows you to define vertex blend procedures (see "Using the Vertex Blend Type Form," below).

Using the Edge Blend Type Form

To open the Edge Blend Type form (see below), click the Edge command button on the Blend Real Volumes form.

The Edge Blend Type form includes the following specifications.

Edges specifies the edge(s) to which the blend procedure definition is to apply.
Define specifies that an edge blend procedure is to be defined the specified edge(s).
Remove (edge delete command, onlyblend option) spec­ifies that any currently defined blend specifications are to be removed from the specified edge(s).
Options:
Constant radius round specifies a constant-radius round blend.
Radius specifies the radius of a constant-radius round blend.
Variable radius round specifies a variable-radius round blend.
Start radius specifies the start endpoint radius of a variable-radius round blend.
End radius specifies the end endpoint radius of a variable-radius round blend.
Constant chamfer specifies a constant-chamfer blend.
Left Range specifies the left range value for the blend.
Right Range specifies the right range value for the blend.
Start Setback specifies the setback value applicable at the start endpoint vertex of the specified edge.
End Setback specifies the setback value applicable at the end endpoint vertex of the specified edge.

Using the Vertex Blend Type Form

To open the Vertex Blend Type form (see below), click the Vertex command button on the Blend Real Volumes form.

The Vertex Blend Type form includes the following specifications.

Vertices specifies one or more vertices to which the current blend definition applies.
Define specifies that a blend procedure is to be defined for the specified vertex (or vertices).
Remove (vertex delete command, onlyblend option) spec­ifies that any currently defined blend specifications are to be removed from the specified vertex (or vertices).
Bulge specifies the bulge shape factor for the vertex blend procedure. (Allowable values: 0 Bulge 2.)
Setback specifies the setback value for the vertex blend procedure.


2.5.5 Modify Volume Color/Label

The Modify Volume Color/Label command button allows you to perform two operations.

Symbol Operation Description
Modify Volume Color Changes the color of the geometry, mesh, and shading associated with one or more volumes as displayed in the graphics window
Modify Volume Label Changes a volume label

The following sections describe the procedures and specifications required to execute the operations listed above.


Modify Volume Color

The Modify Volume Color operation (volume modify command) changes the displayed color of the geometry and/or mesh and/or shading associated with one or more volumes.

Using the Modify Volume Color Form

To open the Modify Volume Color form (see below), click the Modify Color command button on the Geometry/Volume subpad.

The Modify Volume Color form includes the following specifications.

Volume specifies one or more volumes for which the color is to be changed.
Color:
Geometry specifies modifying the color of the volume(s).
Mesh specifies modifying the color of the mesh associated with the volume(s).
Shade specifies modifying the color of the shading associated with the volume(s).

For specific instructions on setting the Geometry, Mesh, or Shade colors, see Section 2.2.4.


Modify Volume Label

The Modify Volume Label operation (volume modify command) changes the label associated with any volume.

Using the Modify Volume Label Form

To open the Modify Volume Label form (see below), click the Modify Label command button on the Geometry/Volume subpad.

The Modify Volume Label form includes the following specifications.

Volume specifies the volume to be modified.
Label specifies a new label for the volume. (See Section 2.1.1.)


2.5.6 Move/Copy/Align Volumes

The Move/Copy/Align Volumes command button allows you to perform two operations.

Symbol Operation Description
Move/Copy Volumes Moves and copies volumes
Align Volumes Aligns volumes and connected geometry with existing topological entities

The following sections describe the procedures and specifications required to execute the operations listed above.


Move/Copy Volumes

The Move/Copy Volumes operation (volume copy, volume move, volume cmove, volume reflect, volume creflect, volume scale, and volume cscale com­mands) repositions and/or reorients one or more volumes or creates copies of volumes. For a general description of the procedures and specifications required to move and/or copy entities, see "Moving an Entity" and "Copying an Entity," respectively, in Section 2.1.4.

Using the Move/Copy Volumes Form

To open the Move/Copy Volumes form (see below), click the Move/Copy command button on the Geometry/Volume subpad.

For a complete description of the specifications available on the Move/Copy Volumes form, see "Using Move/Copy Forms" in Section 2.1.4.


Align Volumes

The Align Volumes operation (volume align command) repositions a set of one or more volumes with respect to a set of translation, rotation, and plane-alignment vertices. (For a general description of the procedure and specifications required to align an entity, see "Aligning an Entity," in Section 2.1.4.)

Using the Align Volumes Form

To open the Align Volumes form (see below), click the Align command button on the Geometry/Volume subpad.

For a complete description of the specifications available on the Align Volumes form, see "Using Align Forms" in Section 2.1.4.


2.5.7 Split/Merge Volumes

The Split/Merge Volumes command button allows you to perform the following operations.

Symbol Operation Description
Split Volume Splits an existing volume into a set of real or virtual volumes
Merge Volumes Merges two or more existing volumes into a virtual volume

The following sections describe the procedures and specifications required to execute the operations listed above.


Split Volume

The Split Volume operation (volume split command) splits an existing volume into a set of real or virtual volumes. To perform the operation, you must specify the following parameters:

The target volume specifies the volume to be split by the Split Volume operation. The split type specifies the type of split tool to be used for the split (volumes, faces, or locations) and the type of geometry to be produced from the operation (real or virtual).

NOTE: Geometry that fails GAMBIT geometry checks ("bad" geometry) can sometimes cause split operations to fail. By default, if a split operation fails due to bad geometry, GAMBIT aborts the operation. For split operations that involve only two entities, however, it is possible to specify that instead of aborting the procedure, GAMBIT auto­matically attempts to smooth and/or heal the geometry and retries the split operation. This specification is made by means of the GEOMETRY.VOLUME.BOOLEAN_METHOD default variable. Specifically, if you set the GEOMETRY.VOLUME.BOOLEAN_METHOD default variable to 2, GAMBIT performs the automatic smooth/heal-retry operation.
NOTE (2): If you set the GEOMETRY.VOLUME.BOOLEAN_METHOD default variable to 3, GAMBIT attempts to preserve existing vertex, edge, and face labels when performing a volume split operation.

Specifying the Target Volume

You can use the Split Volume operation to split either a real or virtual volume; however, the geometry type resulting from the split operation is determined, in part, by the target volume type. Specifically:

NOTE: If you split a volume that serves as a source or attachment entity for a size function, and one of the volumes resulting from the split operation retains the label of the original volume, GAMBIT preserves the size function and assigns it to the volume that retains the original label.

Specifying the Split Type

GAMBIT provides the following volume split type options:

Performing a Volumes (Real) Split-type Operation

The Volumes (Real) split operation allows you to split a real target volume using one or more real split-tool volumes. The split operation results in a set of two or more real volumes the combined shape of which is identical to that of the original target volume. The boundaries between adjacent resulting volumes are defined by the split-tool volume boundary faces in the region of intersection between the target volume and the split-tool volume.

Figure 2-161 illustrates the Volumes (Real) split operation for a configuration involving a cube and a sphere. The cube constitutes the target volume; the sphere constitutes the split tool and is centered at one corner of the cube.

Figure 2-161: Volumes (Real) volume split operation

If you perform a Volumes (Real) split operation using the target and split-tool volumes shown in Figure 2-161(a), GAMBIT creates the set of two volumes shown in Figure 2-161(b). In this case, the boundary face between the two resulting volumes is the surface of one octant of the split-tool sphere.

Specifying the Tolerance Value

GAMBIT allows you to specify the maximum allowable distance (tolerance) between target and split-tool volumes. The Volumes (Real) operation includes two tolerance options:

If you specify the Auto option, GAMBIT automatically computes the tolerance based on an internal algorithm. If you specify the Manual option, GAMBIT allows you to specify a tolerance value (default = 10-5).

Specifying the Resulting Geometry Options

The Volumes (Real) split operation includes three options that determine the geometry condi­tions resulting from the operation:

If you select the Retain suboption, GAMBIT retains the split-tool volume(s) upon completion of the split operation. If you do not select the Retain option, GAMBIT deletes the split-tool volume(s).

If you select the Connected option, GAMBIT connects the volumes that result from the split operation along their common face(s). If you do not select the Connected option, the split operation creates disconnected volumes.

If you select the Bidirectional option, GAMBIT splits and retains the split-tool volume(s) as well as the target volume. For example, Figure 2-162 shows wireframe views of the volumes that result from selection of the Bidirectional option for the split illustrated in Figure 2-161, above.

NOTE: If you select both the Retain and Bidirectional options, GAMBIT retains copies of both the target and split-tool volumes upon completion of the split operation.

Figure 2-162: Volumes (Real) split operation—Bidirectional option

Performing a Faces (Real) Split-type Operation

The Faces (Real) split operation allows you to split a real target volume using one or more real split-tool faces. When you split a volume using the Faces (Real) split option, GAMBIT creates a set of real volumes from the split operation.

Figure 2-163 illustrates the Faces (Real) split operation for a configuration involving a cube that is fully intersected by three circular faces aligned with the coordinate planes (Figure 2-163(a)). If all three circular faces are specified as part of the split-tool set for a Faces (Real) split operation, GAMBIT divides the target volume into eight cubic volumes (Figure 2-163(b)).

Figure 2-163: Faces (Real) volume split operation

The results of the Faces (Real) split operation depend, in part, on whether the faces that constitute the split-tool set intersect the volume fully or partially. If one or more faces fully intersect the volume, GAMBIT creates two or more volumes from the split operation, as shown in Figure 2-163, above. If a split-tool face only partially intersects the volume, GAMBIT creates a dangling face within the target volume that represents the intersection of the split-tool face and target volume.

Specifying the Tolerance Value

GAMBIT allows you to specify the maximum allowable distance (tolerance) between the target volume and split-tool face(s). The Faces (Real) operation includes two tolerance options:

If you specify the Auto option, GAMBIT automatically computes the tolerance based on an internal algorithm. If you specify the Manual option, GAMBIT allows you to specify a tolerance value (default = 10-5).

Specifying the Resulting Geometry Options

The Faces (Real) split operation includes three options that determine the geometry condi­tions resulting from the operation:

If you select the Retain suboption, GAMBIT retains the split-tool face(s) upon completion of the split operation. If you do not select the Retain option, GAMBIT deletes the split-tool face(s).

If you select the Connected option, GAMBIT connects any volumes that result from the split operation along their common face(s). If you do not select the Connected option, the split operation creates disconnected volumes.

If you select the Bidirectional option, GAMBIT splits the split-tool face(s) as well as the volume to be split.

NOTE: If you select both the Retain and Bidirectional options, GAMBIT retains copies of both the target volume and split-tool faces upon completion of the split operation.

Performing a Faces (Virtual) Split-type Operation

The Faces (Virtual) split operation allows you to split a real or non-real target volume using a split-tool face set consisting of one or more real or non-real faces. The split operation is subject to two primary restrictions regarding the faces that can be used to split the volume:

As an example of the first restriction described above, consider the geometric configurations shown in Figure 2-164. Each configuration includes a cubic volume and an internal rectangular face.

Figure 2-164: Faces (Virtual) boundary edge connectivity restriction

In Figure 2-164(a), only two of the four boundary (perimeter) edges (b and d) of the internal face are connected to the surface of the cubic volume—that is, only edges b and d constitute lower-geometry compo­nents of the volume. In this case, the internal face cannot be used to split the cubic volume by means of a Faces (Virtual) split operation, because two of its four boundary (perimeter) edges (a and c) are not connected to the surface of the volume.

In Figure 2-164(b), the upper and lower surfaces of the cubic volume are each composed of two, connected triangular faces (rather than individual square faces). Consequently, all four boundary (perimeter) edges of the internal face (a, b, c, and d) are connected to the cubic volume, and the internal face can be used to split the volume by means of a Faces (Virtual) split operation.

As an example of the second restriction described above, consider the geomet­ric configuration shown in Figure 2-165(a). In this case, the internal face has been split into four separate faces.

Figure 2-165: Faces (Virtual) split operation—internal split-tool face set

If the four internal faces are connected to each other along their common boundary edges, and the edges on the perimeter of the face set are connected to the volume (see Figure 2-165(b)), the set of faces can be successfully used as a split-tool face set for a Faces (Virtual) volume split operation. If the four internal faces are not connected to each other and/or the perimeter of the face set is not completely connected to the volume, the set of faces cannot be used for the volume split operation.

Specifying the Retain Option

The Faces (Virtual) split operation includes a single option that determines the geometry condi­tions resulting from the operation:

If you select the Retain option GAMBIT retains the split-tool face(s) when performing the volume split operation.

Performing a Locations Split-type Operation

The Locations split operation allows you to split a real or non-real target volume using a split-tool consisting of a set of points. If you split a real volume, the operation can produce either real or virtual geometry. If you split a virtual volume, the operation produces only virtual geometry.

To use the Locations option, you must specify a set of points that define the split tool. You can specify any split-tool point by clicking on the volume sur­face to create the point and dragging the point to its final location. (NOTE: Some of the split-tool points must lie on the boundary edges and/or vertices of the faces that bound the volume.) If you specify the Merge resulting edges option, GAMBIT merges the virtual edges into a single edge when performing the split operation.

As an example of the Locations split operation, consider the real, cubic volume and four split points shown in Figure 2-166(a). If you specify split points as shown in the figure and execute the Locations split operation (with the Virtual option selected), GAMBIT splits the appropriate volume boundary edges, creates four straight virtual edges between the split points, constructs a virtual wireframe face from the edges, and uses the face to split the volume. Figure 2-166(b) shows the two virtual volumes resulting from the split operation.

Figure 2-166: Volume split by locations—all split points on boundary edges

NOTE (1): The sequence in which the split points are specified is critical to the successful completion of the Locations split operation. In general, you must specify the split points in a sequence that represents a continuous circuit around the face to be created from the points. For example, in the case shown in Figure 2-166, above, the points can be specified in sequences such as a-b-c-d, c-d-a-b, or b-a-d-c, but not in sequences such as a-d-b-c or c-a-b-.
NOTE (2): If two consecutively specified locations coincide with vertices that lie on a single edge, the edge will constitute part of the boundary of the face used to split the volume. If this condition exists for more than one edge on the target volume, the split operation will fail.
NOTE (3): You can specify whether GAMBIT is allowed to move locations when splitting the volume by means of the GEOMETRY.VOLUME.SPLIT_BY_LOCATIONS default variable—which can be assigned either of two values:
  • 1—(Default) GAMBIT attempts to move the split points to a least-squares plane when splitting the volume
  • 0—GAMBIT does not move the split points when splitting the volume
When attempting to move locations, GAMBIT does not move locations that coincide with vertices or move locations from the faces upon which they were created.

Figure 2-167 shows a Locations split operation (with the Virtual option selected) for which split points are specified on three faces that constitute volume boundary surfaces (points b, d, and f), as well as on three volume boundary edges (points a, c, and e). As in the previous example, GAMBIT creates edges between the split-point locations, creates a face by wireframe from the edges, and uses the face to split the volume.

Figure 2-167: Volume split by locations—split points on edges and faces

NOTE (1): You can specify any number of split-point locations on a given surface (face) of the volume to be split, but the first and last locations specified on any face must lie on the boundary edges of that face. For example, if you specify only points a, b, d, e and f in Figure 2-167, above, GAMBIT will not perform the split operation, because neither the last location specified on the upper face (point b) nor the first location specified on the front face (point d) lies on a boundary edge for its respective face.
NOTE (2): The split-point locations must be specified such that none of the volume boundary surfaces (faces) is split more than once during the split operation. For example, GAMBIT will not split a cylinder lengthwise (along its axis), because the operation would require the cylindrical face to be split in two separate locations.

Specifying the Resulting Geometry Options

The Locations split operation includes two options that determine the geo­metry condi­tions resulting from the operation:

Specifying the Virtual Option

The Virtual option specifies that the volume-split operation produces virtual geometry.

Specifying the Merge resulting edges Option

When splitting the target volume, GAMBIT creates a chain of straight edges between the specified points. The chain of edges serves the boundary of the common face between the split volumes. If you select the Merge resulting edges option, GAMBIT attempts to merge the edges in the edge chain when performing the split operation. (NOTE: The Merge resulting edges option applies only to virtual split operations.) GAMBIT merges adjacent edges only if the angle between them at any shared vertex is greater than the current edge-merge minimum angle (default = 135°). You can change the edge-merge mini­mum angle value by mod­ifying the GEOMETRY.EDGE.VIRTUAL_MERGE_MIN_ANGLE default variable on the Edit Defaults form.

Using the Split Volume Form

To open the Split Volume form (see below), click the Split Volume command button on the Geometry/Volume subpad.

The specifications on the Split Volume form are as follows.

Volume specifies the volume to be split.
Split with
Volumes (Real)
Faces (Real)
Faces (Virtual)
Locations
specifies the split type.

The specifications available on the lower section of the Split Volume form depend on the specified Split with option as follows.

Volumes (Real) Split Option

When you specify the Volumes (Real) option, the lower section of the Split Volume form appears as shown above and includes the following specifications.

Volumes specifies one or more real volumes that constitute the split tool.
Tolerance specifies the maximum allowable distance between the target volume and split-tool volume(s).
  • Auto—Specifies that GAMBIT computes the tolerance value
  • Manual—Allows you to specify a tolerance value (default = 10-5)
Retain retains the split-tool volume(s) at the conclusion of the split operation.
Connected connects the face(s) that constitute(s) the boundary between the volumes resulting from the split operation.
Bidirectional specifies that both the target volume and split-tool volume(s) are split by the split operation.

Faces (Real) Split Option

When you specify the Faces (Real) option, the lower section of the Split Volume form appears as shown below and includes the following specifications.

Faces specifies one or more real faces that constitute the split-tool.
Tolerance specifies the maximum allowable distance between the target volume and split-tool face(s).
  • Auto—Specifies that GAMBIT computes the tolerance value
  • Manual—Allows you to specify a tolerance value (default = 10-5)
Retain retains the split-tool face(s) at the conclusion of the split operation.
Connected connects the faces(s) that constitute(s) the boundary between the volumes resulting from the split operation.
Bidirectional specifies that both the target volume and split-tool face(s) are split by the split operation.

Faces (Virtual) Split Option

When you specify the Faces (Virtual) option, the lower section of the Split Volume form appears as shown below and includes the following specifications.

Faces specifies the faces that constitute the split tool.
Retain retains the split-tool face(s) at the conclusion of the split operation.

Locations Split Option

When you specify the Locations option, the lower section of the Split Volume form appears as shown below and includes the following specifications.

Locations specifies the points that are used to create the split tool.
U Value specifies the u-value location of the current split-tool point with respect to the target-volume boundary surface.
V Value specifies the v-value location of the current split-tool point with respect to the target-volume boundary surface.
Coordinate Sys. specifies the coordinate system with respect to which the current coordinates are specified.
Type specifies the type of coordinate parameters to be used in defining the point.
Cartesian
Cylindrical
Spherical
specifies the type of coordinate parameters to be used in defining the point.
Global | Local specifies the location of the point with respect to either the Global or Local system.
Virtual creates virtual geometry from the split operation.
Merge resulting edges merges the edges resulting from interconnection of the split-tool points to create a single edge at the conclusion of the split operation.


Merge Volumes

The Merge Volumes operation (volume merge command) merges real or virtual volumes into a single real or virtual volume.

When you merge volumes by means of the Merge Volumes form, GAMBIT creates a single real or virtual volume from the set of specified real and/or virtual volumes. Each volume in the set of specified volumes must be connected to at least one other volume in the set by means of a shared, connected face. (NOTE: GAMBIT deletes the shared faces in the process of merging the volumes.)

During virtual merge operations, GAMBIT deletes the volume mesh from the volumes being merged. However, GAMBIT automatically preserves existing meshes on faces that are not deleted in the merge operation.

NOTE: If you merge a set of volumes one of which serves as a source or attach­ment entity for a size function, and the volume that results from the merge operation retains the label of the source or attachment volume, GAMBIT preserves the size function and assigns it to the new volume.

Using the Merge Volumes Form

To open the Merge Volumes form (see below), click the Merge command button on the Geometry/Volume subpad.

The Merge Volumes form includes the following specifications.

Volumes specifies two or more volumes to be merged.
Real specifies that the merged volume is real.
Virtual specifies that the merged volume is virtual.


2.5.8 Smooth/Heal/Convert Volumes

The Smooth/Heal/Convert Volumes command button allows you to perform the following operations.

Symbol Operation Description
Smooth/Heal Real Volumes Smoothes and heals real volume geometry
Convert Volumes (Nonreal to Real) Converts non-real volumes to real volumes

The following sections describe the procedures and specifications required to execute the operations listed above.


Smooth/Heal Real Volumes

The Smooth/Heal Real Volumes operation (volume smooth geometry and volume heal commands) attempts to repair geometry problems associated with model volumes.

Overview

GAMBIT real geometry operations employ ACIS modeling techniques. ACIS modeling algorithms require a high degree of precision and accuracy in the geometric data that describe the model. Such precision and accuracy manifests in the form of tight distance tolerances and completeness of connectivity information.

In most cases, model geometry data generated from within GAMBIT automatically meet the stringent integrity standards required by the ACIS modeler. However, a few GAMBIT operations can sometimes produce geometry that fails to meet the ACIS standards. In addition, geometry imported to GAMBIT from outside sources may not meet such standards due to any of the following factors:

The Smooth/Heal Real Volumes command provides two options for repairing problems such as those described above: The Smooth faces option invokes "smoothing" operations to eliminate conditions on the volume faces that might cause problems for the ACIS modeler. The Heal geometry option employs a three-step process to repair geometry and topology problems.

Specifying the Smooth faces Option

The Smooth faces option allows you to automatically "smooth" the volume faces and edges to repair conditions that might cause problems for the ACIS modeler. It includes the following options:

Both options reconstruct the underlying surface associated with any face being smoothed, and both employ "tolerant" modeling, which assigns tolerance values to faces and their associated edges and vertices, as necessary, to ensure valid topology. (For more information regarding tolerant modeling, see "Import­ing ACIS Files" in Section 4.1.9 of the GAMBIT User’s Guide.)

In addition to these two options, GAMBIT allows you to specify a Tolerance option. The Tolerance option determines the maximum allowable distance that the spline control points can be moved during the smooth operation.

NOTE (1): When you select the Smooth faces option, GAMBIT automatically smoothes the edges associated with the specified faces (see "Smooth Real Edges," in Section 2.3.6.)
NOTE (2): The face-smooth operation should be performed as soon as possible after the specified faces are created or imported. Doing so reduces the chances of the migration of any discontinuities into other geometry and simplifies the task of smoothing.
NOTE (3): The face-smooth operation should involve as many faces at one time as possible, because the smoothing algorithm takes advantage of fact that one geometrical entity can support multiple topological entities.

Replace bad geometry Option

When you select the Replace bad geometry option, GAMBIT detects any bad geometry (including geometry with G1 and C1 discontinuities) and attempts to repair the geometry.

Reduce complexity Option

When you select the Reduce complexity option, GAMBIT attempts to reduce the number of control points in the spline definition of the underlying surfaces and curves.

Specifying the Tolerance Option

When you select the Replace bad geometry or Reduce complexity option, you can also specify a Tolerance option. The Tolerance option determines the maximum allowable distance that the spline control points can be moved.

GAMBIT provides two Tolerance options:

If you specify the Auto option, GAMBIT automatically computes the tolerance based on the size(s) of the specified entities. If you specify the Manual option, GAMBIT allows you to specify a tolerance value (default = 10-3).

Specifying the Heal geometry Option

The Heal geometry option attempts to detect and repair geometry and topology problems that involve the specified face entities. Such problems include curve and surface definitions that do not match the volume topology. The healing operation is involves simplifying geometry and recomputing geometry to repair geometry and topology problems. The steps are associated with the following Heal geometry suboptions:

In the geometry simplification step, GAMBIT converts NURBS data to ana­lytic data, where possible, to within a specified tolerance. In the geometry-repair step, GAMBIT attempts to change surface and edge definitions (if possible) so that the boundaries of the entities in the model "fit together."

NOTE: The GAMBIT Heal geometry operations are not guaranteed to correct all geometry and topology problems in a given model. In general, both operations should be used with caution, because they are not robust and sometimes produce peculiar model geometry.

Simplify geometry Option

The Simplify geometry option allows you to specify whether or not GAMBIT employs geometry simplification when healing volumes. If you select the Simplify geometry option, you can also specify the Tolerance option. The Tolerance option determines whether or not spline surfaces can be approximated by analytic surfaces. If the Tolerance is too loose, approximate analytic fits to spline geometry may be obtained. In such cases, the gaps between surfaces may increase, and healing in subsequent steps may be more difficult or may fail.

GAMBIT provides two Simplify geometry:Tolerance options:

If you specify the Auto option, GAMBIT automatically computes the tolerance. If you specify the Manual option, GAMBIT allows you to specify a tolerance value (default = 10-4).

Repair geometry Option

When you specify the Repair geometry option, GAMBIT attempts to repair the model geometry by recomputing and/or extending surface and curve defini­tions so that the model "fits together" properly. The Make tolerant option (which is always on) creates tolerant geometry, where necessary, to ensure valid topology. (For more information regarding the Make tolerant option, see "Import­ing ACIS Files" in Section 4.1.9 of the GAMBIT User’s Guide.)

When you specify the Repair geometry option, GAMBIT attempts to repair the model geometry by recomputing and/or extending surface and curve defini­tions so that the model "fits together" properly. The Make tolerant option (which is always on) creates tolerant geometry, where necessary, to ensure valid topology. (For more information regarding the Make tolerant option, see "Import­ing ACIS Files" in Section 4.1.9 of the GAMBIT User’s Guide.)

In addition to creating tolerant geometry, the Make tolerant option causes GAMBIT to automatically detect and remove short edges and sliver faces during the healing operation. (NOTE: A "sliver" face is defined as a face with multiple boundary edges that possesses a region narrower than a specified distance.)

You can control the short-edge and sliver-face detection and removal operations by means of two default variables:

To specify that short edges and sliver faces are not removed during healing, set each of these default variables to zero (0).

NOTE: It is inadvisable to use the Repair geometry option on the first attempt at healing the geometry. The operation is computationally intensive and can sometimes produce bad geometry.

Using the Smooth/Heal Real Volumes Form

To open the Smooth/Heal Real Volumes form (see below), click the Smooth/Heal command button on the Geometry/Volume subpad.

The specification on the Smooth/Heal Real Volumes form is as follows.

Volumes specifies the faces for which GAMBIT attempts the repair opera­tions.
All
Pick
  • All specifies all faces in the model.
  • Pick specifies faces selected by means of the Faces list box.
Smooth faces attempts to smooth the surfaces and curves of the volume(s).
Replace bad geometry attempts to reconstruct the specified volumes to replace bad geometry.
Reduce complexity attempts to reduce the number of control points for the underlying surfaces and curves.
Tolerance specifies the maximum distance by which a control point can be moved.
  • Auto—Specifies that GAMBIT computes the tolerance based on the size(s) of the specified entities
  • Manual—Allows you to specify a tolerance value (default = 10-3)
Heal geometry attempts to heal model geometry.
Simplify geometry attempts to simplify geometry during the healing operation.
Tolerance specifies a simplification tolerance value.
  • Auto—Specifies that GAMBIT computes the tolerance
  • Manual—Allows you to specify a tolerance value (default = 10-4)
Repair geometry attempts to repair the model geometry by redefining surfaces and curves so that the model "fits together" properly.
Make tolerant (always on) creates tolerant geometry, where necessary, to ensure valid topology.


Convert Volumes (Nonreal to Real)

The Convert Volumes (Nonreal to Real) operation (volume convert command) converts one or more non-real (faceted and/or virtual) volumes to real volumes. The conversion process preserves both the topology and any existing mesh(es) associated with the converted volume(s). In addition, all non-real faces, edges, and vertices associated with the volume(s) are converted to real faces, edges, and vertices, respectively.

NOTE (1): A non-real volume cannot be converted to a real volume unless all lower topology associated with the non-real volume is also capable of conversion. This restriction requires that all faces of the non-real volume include mapped meshes (see "Convert Faces (Nonreal to Real)," above). In addition, GAMBIT cannot convert volumes for which guest/host relationships exist.
NOTE (2): Hidden entities that serve as hosts for virtual entities may become active (that is, visible) when their guest entities are converted to real geometry.

Using the Convert Volumes (Nonreal to Real) Form

To open the Convert Volumes (Nonreal to Real) form (see below), click the Convert command button on the Geometry/Volume subpad.

The Convert Volumes (Nonreal to Real) form includes the following specification.

Volumes specifies which non-real volumes are to be converted to real volumes.
All
Pick
  • All specifies all volumes in the model.
  • Pick specifies volumes selected by means of the Volumes list box.


2.5.9 Summarize/Check/Query Volumes and Total Entities

The Summarize/Check/Query Volumes and Total Entities command button allows you to perform the following operations.

Symbol Operation Description
Summarize Volumes Displays volume summary information in the Transcript window

Check Volumes

Checks the topological and geometrical validity of model volumes
Query Volumes Opens the volume query list
Total Entities Displays in the Transcript window the total number of entities of one or more specified types

The following sections describe the procedures and specifications required to execute the operations listed above.


Summarize Volumes

The Summarize Volumes operation (volume summarize command) displays volume summary information in the Transcript window.

Using the Summarize Volumes Form

To open the Summarize Volumes form (see below), click the Summarize command button on the Geometry/Volume subpad.

The Summarize Volumes form includes the following specifications.

Volumes specifies the volumes for which information is to be summarized in the Transcript window.
All
Pick
  • All specifies all volumes in the model.
  • Pick specifies volumes selected by means of the Volumes list box.


Check Volumes

The Check Volumes operation (volume check command) assesses the topological and/or geometrical validity of volumes in the model and summarizes the results in the Transcript window.

When you execute the Check Volumes command, GAMBIT checks the model to determine its validity with respect to either or both of the following types of characteristics:

Topology refers to the spatial relationships between entities. Geometry refers to proximity and shape characteristics of the model.

Topology Check

Topological validity is an assessment of the underlying organization of the model-for example, the correct associations between a face entity and the edges that comprise its boundaries or between entities that are associated with each other by virtue of a virtual-geometry, guest-host relationship.

For a given volume, the Check Volumes topology check operation examines the model to ensure that it meets the following criteria:

NOTE (1): Failure of the topology check for any volume in the model constitutes a serious problem for the model as a whole. GAMBIT does not currently include any tools that allow you to repair problems that cause failures of topology checks.
NOTE (2): GAMBIT can automatically check the validity of all input and output (created) entities for any geometry operation and display warning or error messages in the Transcript window for any entity that fails the check(s). The automatic-checking behavior is specified by means of the GEOMETRY.GENERAL.CHECK_LEVEL default variable, which can be set to any of the following values.
  • 0—Do not automatically check input or output entities.
  • 1—(Default) Automatically check output entities; display a warning message for any entity that fails the check(s).
  • 2—Automatically check input and output entities; display a warning message for any entity that fails the check(s).
  • 3—Automatically check input and output entities; display an error message and abort the operation.

Geometry Check

Geometrical validity is an assessment of the model with respect to proximity and shape characteristics-such as the distances between connected edges and/or the mathematical continuity of model curves and surfaces. The Check Volumes geometry check criteria are as follows:

NOTE: Volume healing operations (see Section 2.5.8) may apply to volumes that fail the geometry check.

Using the Check Volumes Form

To open the Check Volumes form (see below), click the Check command button on the Geometry/Volume subpad.

The Check Volumes form includes the following specifications.

Volumes specifies the volumes to be included in the checking operations.
All
Pick
  • All specifies all volumes in the model.
  • Pick specifies volumes selected by means of the Volumes list box.
Check Topology specifies a topology check on the selected volumes.
Check Geometry specifies a geomtery check on the selected volumes.


Query Volumes

The Query Volumes operation (no corresponding command-line command) allows you to identify the locations and/or labels of individual volumes or subsets of volumes in the model. Its use is similar to that of the Query Vertices command (see "Query Vertices" in Section 2.2.7, above).

Using the Query Volumes Form

To open the Query Volumes form (see below), click the Query command button on the Geometry/Volume subpad.

For a general description of the Query Volumes form, see "Using the Query Vertices Form" in Section 2.2.7, above.


Total Entities

The Total Entities operation (list totals command) displays in the Transcript window the total number of geometry and/or mesh entities that currently exist in the model. For example, if you select only the Geometry entities option on the Total Entities form and click Apply, GAMBIT displays in the Transcript window the total numbers of vertices, edges, faces, volumes, groups, and coordinate systems that currently exist in the model.

Using the Total Entities Form

For a description of the options available on the Total Entities form, see "Total Entities," in Section 2.2.7.


2.5.10 Delete Volumes

The Delete Volumes operation (volume delete command) deletes one or more volumes from the model.

Retaining Volume Faces

By default, when you delete a volume, GAMBIT deletes the faces—including their edges and vertices—that constitute parts of the volume. To retain the faces when the volume is deleted, unselect the Lower Geometry option at the bottom of the Delete Volumes form. When you delete a volume and retain its faces, the resulting faces are connected to each other by means of their common edges and vertices.

NOTE: When you delete a volume, GAMBIT does not delete its faces, edges, and vertices that constitute components of other volumes.

Deleting Associated Vertices

When you delete a volume with associated vertices created by means of the Create Vertex On Volume command, GAMBIT deletes any virtual vertices that are associated with the volume. (The virtual vertex cannot exist without the host volume.)

Deleting Virtual Volumes

If you delete a virtual volume, GAMBIT deletes all lower topology and virtual hierarchy that is associated with the volume and is not associated with any other entities in the model.

Using the Delete Volumes Form

To open the Delete Volumes form (see below), click the Delete command button on the Geometry/Volume subpad.

The Delete Volumes form includes the following specifications.

Volumes specifies one or more volumes to be deleted.
All
Pick
  • All specifies all volumes in the model.
  • Pick specifies volumes selected by means of the Volumes list box.
Lower Geometry specifies that all faces, edges, and vertices that constitute parts of the volumes are deleted.


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