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5.4 Geometry Cleanup Operations

5.4.1 Overview

GAMBIT geometry cleanup operations allow you to easily remove unwanted geometric configurations (such as short edges, cracks, and holes) from the model. They aid such removal operations by identifying the unwanted configurations, displaying itemized lists of the associated geometries, and providing a simple means of executing the commands necessary to repair (remove) the configurations.

NOTE: When you open any geometry cleanup form, GAMBIT automatically selects the user-specified pivot-point option for model manipulation and sets the graphics-window color display to the connectivity mode. To restore the pivot-point and color modes to their default settings, click the Select Pivot and Specify Color Mode pushbuttons on the Global Control toolpad (see Section 3.4 in the GAMBIT User's Guide).

The following sections describe the GAMBIT commands used to clean up existing geometry.

5.4.2 Geometry Cleanup Commands

The Tools/Geometry-Cleanup subpad includes the following commands.

Symbol Command(s) Description
Clean Up Short Edges Removes short edges by connecting vertices or merging edges or faces
Clean Up Holes Removes holes by creating faces from the edge loops that define the holes
Clean Up Cracks Removes cracks by connecting the edges that define the cracks
Clean Up Sharp Angles Removes sharply angular face regions by merging them with other faces
Clean Up Large Angles Removes large angles between faces by merging the faces
Clean Up Small Faces Removes small faces by merging or collapsing the faces
Clean Up Hard Edges Removes hard edges on faces
Clean Up Fillets Removes fillets by merging or collapsing the fillet faces
Select Cleanup Domain Specifies the region of the model to which the current cleanup operation is to apply


Clean Up Short Edges

The Clean Up Short Edges command removes short edges from the model, either by replacing them with vertices or by merging the edges with adjacent edges or faces. Regardless of the original geometry type of the edge to be removed, the Clean Up Short Edges operation produces virtual geometry.

As an example of the Clean Up Short Edges operation, consider the simple, square face shown in Figure 5-55(a), one boundary of which includes a very short edge (edge.6). If you execute the Clean Up Short Edges operation for this geometry using the Method:Vertex connect option (see "Specifying the Method," below), GAMBIT replaces edge.6 with a single vertex labeled v_vertex.7 (see Figure 5-55(b)). The exact location of the new vertex depends on the Vertex connect:Location suboption used. For example, if you specify the Average suboption, GAMBIT locates the new vertex midway between the original endpoint vertices of edge.6.

Figure 5-55: Clean Up Short Edges operation

To remove an edge from the model by means of the Clean Up Short Edges operation, you must specify the following para­meters:

Specifying the Edges

To specify an edge for removal from the model, you must select the edge from a list of candidate edges (Items) that are subject to the Clean Up Short Edges operation. To display the list of candidate edges, you must specify two parameters:

The Cleanup domain specifies the region of the model (either the total model or any individual geometric group) currently subject to cleanup operations. You can specify the Cleanup domain by means of the Select Cleanup Domain form (see "Select Cleanup Domain," below).

The Maximum length value specifies the maximum arc length for candidate edges to be included in the Items list (see below). By default, the Maximum length is 10 times greater than the length of the shortest edge in current Cleanup domain.

Working with the Items List

The Items list on the Clean Up Short Edges form contains a list of edges (items) that are candidates for cleanup operations based on the current Cleanup domain and Maximum length criteria. (NOTE: GAMBIT does not automatically update the Items list when you change the Maximum length criteria. To update the Items list based on the current criteria, click the Update button located adjacent to the Items heading.) To specify an edge for the cleanup opera­tion, you must select its label in the Items list. When you select any edge label in the Items list, GAMBIT highlights the corresponding edge in the graphics window.

A vertical array of pushbuttons adjacent to the Items list allows you to perform the following operations:

GAMBIT displays the length of the currently selected edge in the Current length field located immedi­ately below the Items list.

Manipulating the Graphical Display of a Selected Item

All GAMBIT Geometry Cleanup specification forms, including the Clean Up Short Edges form, contain a set of controls that allow you to manipulate the graphical display of the selected item. The controls are:

The Zoom pushbuttons allow you to zoom in on (In) or away from (Out) the item currently selected in the Items list. If you select the Auto checkbox, GAMBIT automatically zooms in on the selected item.

The Local options specify which portion of the model is displayed in the graphics window and whether or not the displayed geometry is shaded. GAMBIT provides two Local options:

When you select the Visible option, GAMBIT displays only the selected item and any geometry connected to it. When you select the Shaded option, GAMBIT shades the displayed geometry.

Specifying the Method

GAMBIT provides three Method options for cleaning up short edges:

Vertex connect Method

When you specify the Vertex connect method, GAMBIT removes the selected edge from the model by deleting the edge and connecting its endpoint vertices to create a single vertex in its place. The Vertex connect method includes three Vertex location options for locating the vertex that results from the connect operation:

where vertex­_a and vertex_b represent the labels for the endpoint vertices of the selected edge.

When you select the Average option, the new vertex resulting from the Vertex connect operation is located midway between the original endpoint-vertex locations. When you select either of the Preserve options, GAMBIT locates the new vertex at the specified (Preserve vertex) location.

Edge merge Method

When you specify the Edge merge method, GAMBIT removes the selected edge by merging it with an adjacent edge specified by means of the Merge with pick list.

Face merge Method

When you specify the Face merge method, GAMBIT removes the selected edge by merging a face to which it is connected with an adjacent face. The faces to be merged are specified by means of the Faces to merge pick list.

Using the Clean Up Short Edges Form

To open the Clean Up Short Edges form (see below), click the Clean Up Short Edges command button on the Tools/Geometry-Cleanup subpad.

The Clean Up Short Edges form includes the following specifications.

Cleanup domain displays the current domain for cleanup operations. By default, the cleanup domain includes all geometric entities in the model. You can restrict the domain to any existing group in the model by means of the Select Cleanup Domain com­mand (see "Select Cleanup Domain," below).
Maximum length specifies the maximum arc length of edges to be included in the Items list.
Default
populates the Maximum length input field with its default value. The default Maximum length is 10 times greater than the minimum arc length in the current Cleanup domain.
Items: lists all edges that are subject to short-edge cleanup operations based on the Maximum length criterion.
Update
updates the Items list based on the current Maximum length criterion.
Apply
removes the selected edge by means of the currently specified Method (see below).
Apply/Next
removes the selected edge from the model and automatically selects the next item in the Items list.
Auto
(Method:Edge merge option only) automatically removes all listed edges by means of the currently specified Method.
Ignore
deletes the selected edge from the Items list, thereby ren­dering it unavailable for cleanup operations.
Restore
restores all previously ignored edges to the Items list.
Current length displays the arc length of the currently selected edge.
Zoom: specifies zoom operations for the graphics window.
In
zooms in on the currently selected edge.
Out
zooms out from the currently selected edge.
Auto automatically zooms in on any edge selected in the Items list.
Local: specifies the display status of the selected edge and any asso­ciated geometry.
Visible displays only the geometry associated with the selected edge and renders the rest of the model invisible. If you unselect the Visible check box, GAMBIT displays the entire model.
Shaded shades the geometry associated with the selected edge.
Method:
Vertex connect
Edge merge
Face merge
specifies the method to be used in the short-edge cleanup operation. For descriptions of the Method options, see "Specifying the Method," above.
Options: contains suboptions associated with each of the three Method operations.
Vertex location: (Method:Vertex connect option only) specifies the location of the vertex resulting from the Vertex connect method. The three Vertex connect options are:
  • Average
  • Preserve vertex_a
  • Preserve vertex_b
For a description of the effects of these suboptions, see "Vertex connect Method," above.
Merge with (Method:Edge merge option only) specifies an edge with which the selected edge is to be merged.
Faces to merge (Method:Merge faces option only) specifies two or more faces that are to be merged to remove the selected edge.


Clean Up Holes

The Clean Up Holes command removes holes from the model by creating faces from the edge loops that define the holes. To eliminate a hole, GAMBIT creates a new face (by wireframe construction) bounded by the edge loop that defines the hole.

As an example of the Clean Up Holes operation, consider the square, planar face shown in Figure 5-56(a). The face contains an internal edge loop that constitutes a "hole." (NOTE: A hole can be bounded by more than one face—for example, a closed-loop gap formed by the boundary edges of two adjacent faces constitutes a hole.) If you execute the Clean Up Holes operation for this geometry, GAMBIT creates a new face (v_face.2) bounded by the edge loop (see Figure 5-56(b)).

Figure 5-56: Clean Up Holes operation

To remove a hole from the model by means of the Clean Up Holes oper­ation, you must specify the hole (as defined by an edge loop) to be removed. The Clean Up Holes oper­ation removes the hole by means of the Create frame from wireframe method, which is not associated with any user-specified options.

Specifying the Hole

To specify a hole for removal from the model, you must select the hole from a list of candidate holes (Items) that are subject to the Clean Up Holes operation. To display the list of candidate holes, you need only specify the Cleanup domain. The Cleanup domain specifies the region of the model (either the total model or any individual geometric group) currently subject to cleanup operations. GAMBIT automatically searches the Cleanup domain for edge loops that constitute holes. You can specify the Cleanup domain by means of the Select Cleanup Domain form (see "Select Cleanup Domain," below).

Working with the Items List

The Items list on the Clean Up Holes form contains a list of holes (edge loops) that are candidates for cleanup operations based on the current Cleanup domain criterion. To specify a hole for the cleanup opera­tion, you must select its corresponding edge loop in the Items list. (For a description of the general procedures required for updating and working with the Items list, see "Clean Up Short Edges," above.)

Manipulating the Graphical Display of a Selected Item

The Clean Up Holes specification form includes a set of controls that allow you to manipulate the graphical display of the selected hole. For instructions concerning the use of the controls, see "Clean Up Short Edges," above.

Using the Clean Up Holes Form

To open the Clean Up Holes form (see below), click the Clean Up Holes command button on the Tools/Geometry-Cleanup subpad.

The Clean Up Holes form includes the following specifications.

Cleanup domain displays the current domain for cleanup operations. By default, the cleanup domain includes all geometric entities in the model. You can restrict the domain to any existing group in the model by means of the Select Cleanup Domain com­mand (see "Select Cleanup Domain," below).
Items: lists all holes (denoted by edge loops) that are subject to cleanup operations.
Update
updates the Items list according to the geometry of the current Cleanup domain.
Apply
removes the selected hole from the Cleanup domain by means of the Create face from wireframe method.
Apply/Next
removes the selected hole from the Cleanup domain and automatically highlights (selects) the next item in the Items list.
Auto
automatically eliminates all listed holes from the Cleanup domain by means of the Create face from wireframe method.
Ignore
deletes the selected hole from the Items list, thereby ren­dering it unavailable for cleanup operations.
Restore
restores all previously ignored holes to the Items list.
Zoom: specifies zoom operations for the graphics window.
In
zooms in on the currently selected hole.
Out
zooms out from the currently selected hole.
Auto automatically zooms in on any hole selected in the Items list.
Local: specifies the graphic display of the currently selected hole and any associated geometry.
Visible displays only the geometry associated with the selected hole and renders the rest of the model invisible. If you unselect the Visible check box, GAMBIT displays the entire model.
Shaded shades the geometry associated with the selected hole.
Method: specifies the method to be used in the crack cleanup operation. (NOTE: The only method currently available for hole cleanup is Create face from wireframe.)


Clean Up Cracks

The Clean Up Cracks command removes cracks from the model by connecting the edges that define the cracks. For the purposes of the geo­metry cleanup operations, a "crack" is defined as a geometry consisting of an edge pair that meets the following criteria.

To clean up a crack, GAMBIT connects the two edges that comprise the crack, thereby replacing the crack with a single edge.

As an example of the Clean Up Cracks operation, consider the two faces shown in Figure 5-57(a), each of which is bounded by four straight edges. The two adjacent edges that separate the faces from each other (edge.4 and edge.8) share a common endpoint vertex (vertex.5) at one end and are separated by a small gap at the other—therefore, they constitute a "crack."

Figure 5-57: Clean Up Cracks operation, one common endpoint vertex

If you execute the Clean Up Cracks operation for this geometry, GAMBIT connects edge.4 and edge.8 to create a single edge (v_edge.9), thereby replacing the crack with a single edge and creating a common boundary between the two faces (see Figure 5-57(b)).

As noted above, the edges that comprise a crack can share common endpoint vertices at both ends. For example, Figure 5-58(a) shows a geometry in which the edges that separate two adjacent faces (edge.4 and edge.8) share common endpoint vertices at both ends but are separated by a gap the width of which varies along its length.

Figure 5-58: Clean Up Cracks operation, two common endpoint vertices

As before, if you execute the Clean Up Cracks operation for this geometry, GAMBIT connects edge.4 and edge.8 to create a single edge (v_edge.9), thereby replacing the crack with a single, curved edge and creating a common boundary between the two faces (see Figure 5-58(b)).

To remove a crack from the model by means of the Clean Up Cracks oper­ation, you must specify the following para­meters:

Specifying the Crack

To specify a crack to be removed from the model, you must select the crack (edge pair) from a list of candidate cracks (Items) that are subject to the Clean Up Cracks operation. To display the list of candidate cracks, you must specify two parameters:

The Cleanup domain specifies the region of the model (either the total model or any individual geometric group) currently subject to cleanup operations. You can specify the Cleanup domain by means of the Select Cleanup Domain form (see "Select Cleanup Domain," below). The Maximum angle value specifies the maximum angle between edges for edge pairs that are to be included in the Items list (see below). GAMBIT computes the angle at the endpoint vertex shared by the edges. If two edges that comprise a crack share common endpoint vertices at both ends, GAMBIT computes the angle at both vertices and uses the lesser of the two angles to determine whether or not to include the edge pair in the Items list. By default, the Maximum angle is 20°.

Working with the Items List

The Items list on the Clean Up Cracks form contains a list of cracks (edge pairs) that are candidates for cleanup operations based on the current Cleanup domain and Maximum angle criteria. To specify a crack for the cleanup opera­tion, you must select its corresponding edge pair in the Items list. (For a description of the general procedures required for updating and working with the Items list, see "Clean Up Short Edges," above.) The Current angle field, located immedi­ately below the Items list, displays the angle for the currently selected crack.

Manipulating the Graphical Display of a Selected Item

The Clean Up Cracks specification form includes a set of controls that allow you to manipulate the graphical display of the selected crack. For instructions concerning the use of the controls, see "Clean Up Short Edges," above.

Specifying the Tolerance Option

GAMBIT allows you to control the Connect edges operation used to remove the currently selected crack by means of a Tolerance option. The Tolerance option specifies the maximum allowable separation distance between edges to be connected. It is expressed (and input) as a percentage of the shortest length of the currently selected edge pair. When you select a crack for removal, GAMBIT computes the separation distance between edges along the length of the crack. GAMBIT performs the edge-connect operation only if the separation does not exceed the Tolerance value at any point along the length of the crack.

Using the Clean Up Cracks Form

To open the Clean Up Cracks form (see below), click the Clean Up Cracks command button on the Tools/Geometry-Cleanup subpad.

The Clean Up Cracks form includes the following specifications.

Cleanup domain displays the current domain for cleanup operations. By default, the cleanup domain includes all geometric entities in the model. You can restrict the domain to any existing group in the model by means of the Select Cleanup Domain com­mand (see "Select Cleanup Domain," below).
Maximum angle specifies the maximum angle between edges for cracks to be included in the Items list.
Default
populates the Maximum angle input field with its default value (20°).
Items: lists all cracks (denoted by edge pairs) that are subject to cleanup operations based on the Maximum angle criterion.
Update
updates the Items list based on the current Maximum angle criterion.
Apply
removes the selected crack from the Cleanup domain by means of the Connect edges method.
Apply/Next
removes the selected crack from the Cleanup domain and automatically highlights (selects) the next item in the Items list.
Auto
automatically removes all listed cracks from the Cleanup domain by means of the Connect edges method.
Ignore
deletes the selected crack from the Items list, thereby ren­dering it unavailable for cleanup operations.
Restore
restores all previously ignored cracks to the Items list.
Current angle displays the angle of the cur­rently selected crack.
Zoom: specifies zoom operations for the graphics window.
In
zooms in on the currently selected crack.
Out
zooms out from the currently selected crack.
Auto automatically zooms in on any crack selected in the Items list.
Local: specifies the graphic display of the currently selected crack and any associated geometry.
Visible displays only the geometry associated with the selected crack and renders the rest of the model invisible. If you unselect the Visible check box, GAMBIT displays the entire model.
Shaded shades the geometry associated with the selected crack.
Method: specifies the method to be used in the crack cleanup operation. (NOTE: The only method currently available for hole cleanup is Connect edges.)
Options: contains a suboption associated with the Connect edges operation.
Tolerance specifies the maximum allowable separation between edges to be connected.


Clean Up Sharp Angles

The Clean Up Sharp Angles command removes sharp interior angles from faces by merging the faces with adjacent faces. For the purposes of the geometry cleanup operations, a "sharp angle" is defined as an edge pair that meets the following criteria.

As an example of the Clean Up Sharp Angles operation, consider the two coplanar faces shown in Figure 5-59(a). The faces are connected by a common edge (edge.6), and one of the faces (face.2) contains a sharp interior angle (defined by edge.2 and edge.6).

Figure 5-59: Clean Up Sharp Angles operation

If you execute a simple Clean Up Sharp Angles operation for this geometry and do not specify the Merge faces options (see below), GAMBIT merges face.2 with face.1 to create a single face (v_face.3), thereby removing the sharp interior angle (see Figure 5-59(b)). In this case, GAMBIT also merges the outer boundary edges of the faces into a single virtual edge (v_edge.8); therefore, v_face.3 is bounded by only two edges.

To remove a sharp angle from the model by means of the Clean Up Sharp Angles oper­ation, you must specify the following para­meters:

Specifying the Sharp Angle

To specify a sharp angle to be removed, you must select the sharp angle (as defined by its corresponding edge pair) from a list of candidate angles (Items). To display the list of candidate angles, you must specify two para­meters:

The Cleanup domain specifies the region of the model (either the total model or any individual geometric group) currently subject to cleanup operations. You can specify the Cleanup domain by means of the Select Cleanup Domain form (see "Select Cleanup Domain," below).

The Maximum angle value specifies the maximum angle between edges for edge pairs that are to be included in the Items list (see below). For example, if the Maximum angle is specified as 10°, the Items list will contain all edge pairs in the Cleanup domain that define face boundaries with angles less than or equal to 10°. GAMBIT computes the angle at the endpoint vertex shared by the edges. By default, the Maximum angle is 20°.

Working with the Items List

The Items list on the Clean Up Sharp Angles form contains a list of sharp angles (edge pairs) that are candidates for cleanup operations based on the current Cleanup domain and Maximum angle criteria. To specify a sharp angle for the cleanup opera­tion, you must select its corresponding edge pair in the Items list. (For a description of the general procedures required for updating and working with the Items list, see "Clean Up Short Edges," above.) The Current angle field, located immedi­ately below the Items list, displays the value of the currently selected sharp angle.

Manipulating the Graphical Display of a Selected Item

The Clean Up Sharp Angles specification form includes a set of controls that allow you to manipulate the graphical display of the selected sharp-angle geometry. For instructions concerning the use of the controls, see "Clean Up Short Edges," above.

Specifying the Merge faces Options

GAMBIT provides the following options to control the Merge faces operation used to remove the currently selected sharp angle:

The Merge chop suboptions control the shapes of the faces that result from the Merge faces operation. The Faces to merge option specifies the faces to be merged in the removal of the sharp angle.

Specifying the Merge chop Options

GAMBIT provides two Merge chop suboptions:

If you specify the Chop suboption, GAMBIT creates two new faces from the merge operation, one of which is truncated such that its shortest boundary edge is equal to a specified Distance. When executing the Merge faces operation with the Chop suboption, GAMBIT truncates the first of the two faces listed in the Faces to merge pick list.

If you specify the Bi-chop suboption, GAMBIT creates three new faces from the merge operation. Two of the new faces are truncated such that their shortest boundary edges are equal to the specified Distance; the other repre­sents the merging of the truncated pieces.

Chop Suboption

As an example of the effect of the Chop suboption, consider the sets of faces shown in Figure 5-60(a) and (b). The results shown in this figure illustrate the effect of the Chop suboption on the Clean Up Sharp Angles operation for the face containing a sharp angle (face.2) shown in Figure 5-59(a), above. They differ only in the order in which the faces are specified in the Faces to merge pick list, which determines which face is truncated in the Merge faces operation.

Figure 5-60: Clean Up Sharp Angles operation, Chop suboption

If you specify the Chop suboption and specify face.2 first in the Faces to merge pick list, GAMBIT creates the configuration shown in Figure 5-60(a). In this configuration, GAMBIT truncates face.2 to create v_face.7 and merges the truncated part of face.2 with face.1 to create v_face.6. The length of the boundary edge that defines the truncation of face.2 is equal to the Merge chop:Distance specification.

If you specify the Chop suboption and specify face.1 first in the Faces to merge pick list, GAMBIT creates the configuration shown in Figure 5-60(b). In this configuration, GAMBIT truncates face.1 to create v_face.6 and merges the truncated part of face.1 with face.2 to create v_face.7. As before, the length of the boundary edge that defines the truncation of face.1 is equal to the Merge chop:Distance specification.

Bi-chop Suboption

As an example of the effect of the Bi-chop suboption, consider the geometrical configurations shown in Figure 5-61. Figure 5-61(a) represents an initial con­figuration identical to that shown in Figure 5-59(a), above. Figure 5-61(b) shows the configuration that results from the use of the Bi-chop option.

Figure 5-61: Clean Up Sharp Angles operation, Bi-chop suboption

In this case, GAMBIT creates three new faces—v_face.6, v_face.8, and v_face.9. The first two faces, v_face.6 and v_face.8, represent the truncations of face.1 and face.2, respectively. The third face (v_face.9) is created by merging the truncated parts of face.1 and face.2. In performing the operation, GAMBIT truncates face.1 such that the shortest edges of v_face.9 (v_edge.14 and v_edge.15) are equal in length to the Merge chop:Distance specification.

Specifying the Faces to merge Option

The Faces to merge pick list specifies the faces to be merged to remove the currently selected sharp interior angle. If you select the Merge chop:Chop option, the order in which the faces are selected affects the results of the Merge faces operation. If you select the Merge chop:Bi-chop option or do not specify a Merge chop option, the order in which the faces are selected does not affect the results of the operation.

Using the Clean Up Sharp Angles Form

To open the Clean Up Sharp Angles form (see below), click the Clean Up Sharp Angles command button on the Tools/Geometry-Cleanup subpad.

The Clean Up Sharp Angles form includes the following specifications.

Cleanup domain displays the current domain for cleanup operations. By default, the cleanup domain includes all geometric entities in the model. You can restrict the domain to any existing group in the model by means of the Select Cleanup Domain com­mand (see "Select Cleanup Domain," below).
Maximum angle specifies the maximum angle between adjacent edges for sharp-angle geometries to be included in the Items list.
Default
populates the Maximum angle input field with its default value (20°).
Items: lists all sharp-angle geometries (denoted by edge/vertex combina­tions) that are subject to cleanup operations based on the Maximum angle criterion.
Update
updates the Items list based on the current Maximum angle criterion.
Apply
removes the selected sharp angle from the Cleanup domain by means of the Merge faces method.
Apply/Next
removes the selected sharp angle from the Cleanup domain and automatically highlights (selects) the next item in the Items list.
Auto
automatically removes all listed sharp angles from the Cleanup domain by means of the Merge faces method.
Ignore
deletes the selected sharp-angle geometry from the Items list, thereby ren­dering it unavailable for cleanup operations.
Restore
restores all previously ignored sharp-angle geometries to the Items list.
Current angle displays the angle of the sharp-angle geometry cur­rently selected in the Items list.
Zoom: specifies zoom operations for the graphics window.
In
zooms in on the currently selected sharp-angle geometry.
Out
zooms out from the currently selected sharp-angle geometry.
Auto automatically zooms in on any sharp-angle geometry selected in the Items list.
Local: specifies the graphic display of the currently selected sharp-angle geometry and any associated geometry.
Visible displays only the geometry associated with the selected sharp-angle geometry and renders the rest of the model invisible. If you unselect the Visible check box, GAMBIT displays the entire model.
Shaded shades the geometry associated with the selected sharp-angle geometry.
Method: specifies the method to be used in the small-angle cleanup operation. (NOTE: The only method currently available for hole cleanup is Merge faces.)
Options: contains suboptions associated with the Merge faces operation.
Merge chop contains suboptions and specifications associated with the Merge faces opera­tion. The suboptions are:
  • Chop
  • Bi-chop
For a description of the effects of these suboptions and the Merge chop:Distance specification, see "Specifying the Merge chop Options," above.
Faces to merge specifies one or more faces that are to be merged to remove the selected sharp-angle geometry.


Clean Up Large Angles

The Clean Up Large Angles command removes large angles between faces by merging the faces. For the purposes of the geometry cleanup operations, a "large angle" geometric configuration is defined by a set of faces that meet the following criteria.

As an example of the Clean Up Large Angles operation, consider the two square, planar faces shown in Figure 5-62(a). The faces share a common boundary edge (edge.4) and are oriented such that the angle between their outward pointing normals (computed at the midpoint of their common bound­ary edge) is 10°. The resulting "interior" angle between the faces is 170° (= 180°-10°).

Figure 5-62: Clean Up Large Angles operation

If you execute the Clean Up Large Angles operation for this geometry, GAMBIT replaces the faces with a single, virtual face, v_face.3 (see Figure 5-62(b)).

To remove a large-angle configuration from the model by means of the Clean Up Large Angles operation, you must specify the following para­meters:

Specifying the Large Angle

To specify a large-angle configuration to be removed, you must select the configuration from a list of candidate configurations (Items). To display the list of candidate configurations, you must specify two parameters:

The Cleanup domain specifies the region of the model (either the total model or any individual geometric group) currently subject to cleanup operations. You can specify the Cleanup domain by means of the Select Cleanup Domain form (see "Select Cleanup Domain," below).

The Maximum angle defines a "large-angle configuration" in terms of the angle between the outward-pointing normals for the faces in the configuration (see Figure 5-63). If the angle between the outward-pointing normals () for any pair of connected faces is less than or equal to the Maximum angle specification, GAMBIT includes the associated face set in the Items list of candidate large-angle configurations. The default value of the Maximum angle is 5°.

Figure 5-63: Clean Up Large Angles, Maximum angle specification

To determine whether or not a face pair meets the Maximum angle criterion, GAMBIT computes the face normals at the midpoint and endpoints of the boundary edge shared by the faces and uses the minimum of the three computed angles. This methodology allows you to apply the Clean Up Large Angles operation to face sets that involve non-planar faces, as well as faces the common boundary edge of which is curved.

Working with the Items List

The Items list on the Clean Up Large Angles form contains a list of large-angle configurations (face sets) that are candidates for cleanup operations based on the current Cleanup domain and Maximum angle criteria. To specify a large-angle configuration for the cleanup opera­tion, you must select its corresponding face set in the Items list. (For a description of the general procedures required for updating and working with the Items list, see "Clean Up Short Edges," above.) The Current angle field, located immedi­ately below the Items list, displays the qualifying angle for the currently selected face set.

Manipulating the Graphical Display of a Selected Item

The Clean Up Large Angles specification form includes a set of controls that allow you to manipulate the graphical display of the selected large-angle geometry. For instructions concerning the use of the controls, see "Clean Up Short Edges," above.

Specifying the Faces to Be Merged

To clean up a large-angle configuration, GAMBIT merges the set of faces that constitutes the configuration. You can specify other faces to be merged in the operation by means of the Faces to merge option at the bottom of the Clean Up Large Angles form.

Using the Clean Up Large Angles Form

To open the Clean Up Large Angles form (see below), click the Clean Up Large Angles command button on the Tools/Geometry-Cleanup subpad.

The Clean Up Large Angles form includes the following specifications.

Cleanup domain displays the current domain for cleanup operations. By default, the cleanup domain includes all geometric entities in the model. You can restrict the domain to any existing group in the model by means of the Select Cleanup Domain com­mand (see "Select Cleanup Domain," below).
Maximum angle specifies the maximum angle between connected faces for large-angle geometries to be included in the Items list.
Default
populates the Maximum angle input field with its default value (5°).
Items: lists all large-angle geometries (denoted by face sets and their common edges) that are subject to cleanup operations based on the Maximum angle criterion.
Update
updates the Items list based on the current Maximum angle criterion.
Apply
removes the selected large-angle geometry from the Cleanup domain by means of the Merge faces method.
Apply/Next
removes the selected large-angle geometry from the Cleanup domain and automatically highlights (selects) the next item in the Items list.
Auto
automatically removes all listed large-angle geometries by means of the Merge faces method.
Ignore
deletes the selected large-angle geometry from the Items list, thereby ren­dering it unavailable for cleanup operations.
Restore
restores all previously ignored large-angle geometries to the Items list.
Current angle displays the angle of the large-angle geometry cur­rently selected in the Items list.
Zoom: specifies zoom operations for the graphics window.
In
zooms in on the currently selected large-angle geometry.
Out
zooms out from the currently selected large-angle geometry.
Auto automatically zooms in on any large-angle geometry selected in the Items list.
Local: specifies the graphic display of the currently selected large-angle geometry and any associated geometry.
Visible displays only the geometry associated with the currently selected large-angle geometry and renders the rest of the model invisible. If you unselect the Visible check box, GAMBIT displays the entire model.
Shaded shades the geometry associated with the currently selected large-angle geometry.
Method: specifies the method to be used in the large-angle cleanup operation. (NOTE: The only method currently available for hole cleanup is Merge faces.)
Options: contains suboptions associated with the Merge faces operation.
Faces to merge specifies the faces that are to be merged to eliminate the selected large-angle geometry.


Clean Up Small Faces

The Clean Up Small Faces command removes small faces by merging them with adjacent faces or collapsing them between surrounding faces. Regardless of the original geometry type of the face to be removed, the Clean Up Small Faces operation produces virtual geometry.

As an example of the Clean Up Small Faces operation, consider the two faces shown in Figure 5-64(a), one of which (face.2) is very small. If you execute the Clean Up Small Faces operation for this geometry and specify the Merge faces option, GAMBIT merges face.2 with face.1 to create a single face (v_face.3), thereby removing the small face (see Figure 5-64(b)).

Figure 5-64: Clean Up Small Faces operation

To remove a small face from the model by means of the Clean Up Small Faces oper­ation, you must specify the following para­meters:

Specifying the Small Face

To specify a small face to be removed, you must select the face from a list of candidate faces (Items). To display the list of candidate faces, you must specify two para­meters:

The Cleanup domain specifies the region of the model (either the total model or any individual geometric group) currently subject to cleanup operations. You can specify the Cleanup domain by means of the Select Cleanup Domain form (see "Select Cleanup Domain," below).

The Maximum area value defines a "small face" for the purposes of the cleanup operation. For example, if you specify a Maximum area of 1.0, the Items list will contain all faces in the Cleanup domain the area of which is less than or equal to 1.0. The default value for the Maximum area is 100 times the area of the smallest face in the Cleanup domain.

Working with the Items List

The Items list on the Clean Up Small Faces form contains a list of faces (items) that are candidates for cleanup operations based on the current Cleanup domain and Maximum area criteria. To specify a face for the cleanup opera­tion, you must select its label in the Items list. (For a description of the general procedures required for updating and working with the Items list, see see "Clean Up Short Edges," above.) The Current area field, located immediately below the Items list, displays the area for the currently selected face.

Manipulating the Graphical Display of a Selected Item

The Clean Up Small Faces specification form includes a set of controls that allow you to manipulate the graphical display of the selected face. For instructions concerning the use of the controls, see "Clean Up Short Edges," above.

Specifying the Method

GAMBIT provides the following Method options for cleaning up small faces:

Merge faces Method

When you specify the Merge faces method, GAMBIT removes the selected face by merging it with an adjacent face specified by means of the Faces to merge pick list.

Collapse face Method

When you specify the Collapse face method, GAMBIT removes the selected face by collapsing the face between any connected faces that surround it.

Using the Clean Up Small Faces Form

To open the Clean Up Small Faces form (see below), click the Clean Up Small Faces command button on the Tools/Geometry-Cleanup subpad.

The Clean Up Small Faces form includes the following specifications.

Cleanup domain displays the current domain for cleanup operations. By default, the cleanup domain includes all geometric entities in the model. You can restrict the domain to any existing group in the model by means of the Select Cleanup Domain command (see "Select Cleanup Domain," below).
Maximum area specifies the maximum area for faces to be included in the Items list.
Default
populates the Maximum area input field with its default value (100 times the area of the smallest face in the Cleanup domain).
Items: lists all small faces that are subject to cleanup operations based on the Maximum area criterion.
Update
updates the Items list based on the current Maximum area criterion.
Apply
removes the selected face from the Cleanup domain by means of the currently selected Method (see below).
Apply/Next
removes the selected face from the Cleanup domain and automatically highlights (selects) the next item in the Items list.
Auto
automatically removes all listed faces by means of the currently selected Method (see below).
Ignore
deletes the selected face from the Items list, thereby rendering it unavailable for cleanup operations.
Restore
restores all previously ignored faces to the Items list.
Current area displays the area of the face cur­rently selected in the Items list.
Zoom: specifies zoom operations for the graphics window.
In
zooms in on the currently selected face.
Out
zooms out from the currently selected face.
Auto automatically zooms in on any face selected in the Items list.
Local: specifies the graphic display of the currently selected face and any associated geometry.
Visible displays only the geometry associated with the selected face and renders the rest of the model invisible. If you unselect the Visible check box, GAMBIT displays the entire model.
Shaded shades the geometry associated with the selected face.
Method:
Merge face
Collapse face
specifies the method to be used in the small-face cleanup operation (see "Specifying the Method," above)..
Options: contains suboptions associated with the Method options.
Faces to merge (Merge faces option only) specifies two faces that are to be merged to remove the selected small-face geometry.


Clean Up Hard Edges

The Clean Up Hard Edges command removes hard edges from the model. Hard edges (also known as dangling edges) are those that are included in the list of edges that define a face but which do not constitute necessary parts of the closed edge loop that circumscribes the face. Such edges often result from face-split operations in which the split-tool face only partially intersects the target face. To remove hard edges, GAMBIT executes a Simplify Faces operation for the face to which the hard edges are attached. (For a description of the Simplify Faces operations, see Section 2.4.7 in this guide.)

As an example of the Clean Up Hard Edges operation, consider the square, planar face shown in Figure 5-65(a), the boundary-edge loop of which includes a hard edge (edge.6). If you execute the Clean Up Hard Edges operation for this geometry, GAMBIT removes the hard edge from the face (see Figure 5-65(b)).

Figure 5-65: Clean Up Hard Edges operation

To remove one or more hard edges from a face in the model by means of the Clean Up Hard Edges oper­ation, you need only specify the face that includes the hard edges. The Clean Up Hard Edges oper­ation automatically removes any hard edges on the face and is not associated with any user-specified options.

Specifying the Face

To remove a hard edge from the model, you must select the face to which it is attached from a list of candidate faces (Items) in the current Cleanup domain. The Cleanup domain specifies the region of the model (either the total model or any individual geometric group) currently subject to cleanup operations. You can specify the Cleanup domain by means of the Select Cleanup Domain form (see "Select Cleanup Domain," below).

Working with the Items List

The Clean Up Hard Edges form contains a list of candidate faces (Items) in the current Cleanup domain. To specify a face for which hard edges are to be removed, you must select the candidate face in the Items list. For a description of the general procedures required for updating and working with the Items list, see "Clean Up Short Edges," above.

Manipulating the Graphical Display of a Selected Item

The Clean Up Hard Edges specification form includes a set of controls that allow you to manipulate the graphical display of the selected face. For instructions concerning the use of the controls, see "Clean Up Short Edges," above.

Using the Clean Up Hard Edges Form

To open the Clean Up Hard Edges form (see below), click the Clean Up Hard Edges command button on the Tools/Geometry-Cleanup subpad.

The Clean Up Hard Edges form includes the following specifications.

Cleanup domain displays the current domain for cleanup operations. By default, the cleanup domain includes all geometric entities in the model. You can restrict the domain to any existing group in the model by means of the Select Cleanup Domain com­mand (see "Select Cleanup Domain," below).
Items: lists all faces in the Cleanup domain that contain hard edges.
Update
updates the Items list according to the geometry of the current domain.
Apply
removes all hard edges from the selected face.
Apply/Next
removes all hard edges from the selected face and automatically highlights (selects) the next item in the Items list.
Auto
automatically removes all hard edges from all listed faces.
Ignore
deletes the selected face from the Items list, thereby ren­dering it unavailable for cleanup operations.
Restore
restores all previously ignored faces to the Items list.
Zoom: specifies zoom operations for the graphics window.
In
zooms in on the currently selected face.
Out
zooms out from the currently selected face.
Auto automatically zooms in on any face selected in the Items list.
Local: specifies the graphic display of the currently selected face and any associated geometry.
Visible displays only the geometry associated with the selected face and renders the rest of the model invisible. If you unselect the Visible check box, GAMBIT displays the entire model.
Shaded shades the geometry associated with the selected face.
Method: specifies the method to be used in the hard edge cleanup operation. (NOTE: The only method currently available for hard-edge cleanup is Remove all hard edges on face.)


Clean Up Fillets

The Clean Up Fillets command removes fillets in the model by merging the fillets with adjacent faces or collapsing them between surrounding faces. For the purposes of the geometry cleanup operations, a "fillet" is defined as a face that meets the following criteria.

As an example of the Clean Up Fillets operation, consider the three faces shown in Figure 5-66(a), one of which (face.3) constitutes a fillet. If you execute the Clean Up Fillets operation for this geometry and specify the Collapse face option, GAMBIT creates the configuration shown in Figure 5-66(b).

Figure 5-66: Clean Up Fillets operation, Collapse face option

If you execute the operation with the Merge faces option, GAMBIT merges the fillet face with either of the other (user-specified) faces.

To remove a fillet from the model by means of the Clean Up Fillets oper­ation, you must specify the following para­meters:

Specifying the Fillet

To specify a fillet to be removed, you must select the fillet face from a list of candidate faces (Items). To display the list of candidate faces, you must specify two para­meters:

The Cleanup domain specifies the region of the model (either the total model or any individual geometric group) currently subject to cleanup operations. You can specify the Cleanup domain by means of the Select Cleanup Domain form (see "Select Cleanup Domain," below).

The Maximum angle value specifies the maximum allowable deviation from 90° for outward-pointing normals computed at the boundaries of the fillet face. For example, for face.3 in Figure 5-67 to qualify as a fillet for cleanup, the angle () between outward-pointing normals computed at its relevant boundary edges must not deviate from 90° by more than the specified Maximum angle value.

Figure 5-67: Clean Up Large Angles operation, Maximum angle specification

Working with the Items List

The Items list on the Clean Up Fillets form contains a list of faces (items) that are candidates for cleanup operations based on the current Cleanup domain and Maximum angle criteria. To specify a face for the cleanup opera­tion, you must select its label in the Items list. (For a description of the general procedures required for updating and working with the Items list, see see "Clean Up Short Edges," above.)

NOTE: The Auto operation is not available for the Clean Up Fillets command.

The Current angle field, located immediately below the Items list, displays the angle between outward-pointing normals for the currently selected face.

Manipulating the Graphical Display of a Selected Item

The Clean Up Fillets specification form includes a set of controls that allow you to manipulate the graphical display of the selected face. For instructions concerning the use of the controls, see "Clean Up Short Edges," above.

Specifying the Method

GAMBIT provides the following Method options for cleaning up fillets:

Merge faces Method

When you specify the Merge faces method, GAMBIT removes the selected fillet by merging it with an adjacent face specified by means of the Faces to merge pick list (see Figure 5-66). (NOTE: To execute the Clean Up Fillets operation, you must specify both the fillet face and that face to which it is to be merged.)

Collapse face Method

When you specify the Collapse face method, GAMBIT removes the selected fillet by collapsing it between faces specified by means of the Collapse between pick list.

Using the Clean Up Fillets Form

To open the Clean Up Fillets form (see below), click the Clean Up Fillets command button on the Tools/Geometry-Cleanup subpad.

The Clean Up Fillets form includes the following specifications.

Cleanup domain displays the current domain for cleanup operations. By default, the cleanup domain includes all geometric entities in the model. You can restrict the domain to any existing group in the model by means of the Select Cleanup Domain com­mand (see "Select Cleanup Domain," below).
Maximum angle specifies the maximum angle between outward-pointing normals for faces to be included in the Items list.
Default
populates the Maximum angle input field with its default value (20°).
Items: lists all fillets that are subject to cleanup operations based on the Maximum angle criterion.
Update
updates the Items list based on the current Maximum angle criterion.
Apply
removes the selected fillet from the Cleanup domain by means of the currently specified Method (see below).
Apply/Next
removes the selected fillet from the Cleanup domain and automatically highlights (selects) the next item in the Items list.
Auto
automatically removes all listed fillets by means of the currently specified Method (see below).
Ignore
deletes the selected fillet from the Items list, thereby ren­dering it unavailable for cleanup operations.
Restore
restores all previously ignored fillets to the Items list.
Current angle displays the angle of the fillet cur­rently selected in the Items list.
Zoom: specifies zoom operations for the graphics window.
In
zooms in on the currently selected fillet.
Out
zooms out from the currently selected fillet.
Auto automatically zooms in on any fillet selected in the Items list.
Local: specifies the graphic display of the currently selected fillet and any associated geometry.
Visible displays only the geometry associated with the selected fillet and renders the rest of the model invisible. If you unselect the Visible check box, GAMBIT displays the entire model.
Shaded shades the geometry associated with the selected fillet.
Method:
Merge faces
Collapse face
specifies the method to be used in the fillet cleanup operation.
Options: contains suboptions associated with each Method operation.
Faces to merge (Merge faces option) specifies two faces that are to be merged to eliminate the selected fillet.
Collapse between (Collapse face option) specifies the faces between which the fillet face is to be collapsed.


Select Cleanup Domain

The Select Cleanup Domain command specifies the domain to which the geo­metry cleanup operations apply. The cleanup domain can consist of either the entire model (default) or any individual predefined geometry group. (For information on creating a geometry group, see Section 2.6.1 in this guide.)

Using the Select Cleanup Domain Form

To open the Select Cleanup Domain form (see below), click the Select Cleanup Domain command button on the Tools/Geometry-Cleanup subpad.

The Select Cleanup Domain form includes the following specifications.

Current domain displays the current geometry domain to which cleanup oper­ations apply.
New domain specifies a predefined geometry group to which subsequent cleanup operations are to apply. To specify "whole model" as the cleanup domain:
  1. Click the arrow located at the right side of the New domain pick list box to open the Group List (Single) form.
  2. On the Group List (Single) form, remove all items from the Picked list.
  3. Close the Group List (Single) form.
  4. On the Select Cleanup Domain form, click Apply.


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