On this page:
4.5.1 Splitting Geometry
4.5.1.1 Split Curve
4.5.1.2 Split Periodic Surfaces
4.5.1.3 Split Surface
4.5.1.3.3.1 Logical Rectangle
4.5.1.3.3.2 Split Orientation
4.5.1.3.3.3 Corner Specification
4.5.1.3.3.4 Direction
4.5.1.3.3.5 Segment|Fraction|Distance
4.5.1.3.3.6 Through Vertex
4.5.1.3.3.7 Parametric
4.5.1.3.3.8 Tolerance
4.5.1.3.3.9 Preview
4.5.1.3.3.10 Settings
4.5.2 Web Cutting
4.5.2.2 Web Cutting with an Arbitrary Surface
4.5.2.3 Chop Command
4.5.2.4 Web Cutting with a Planar or Cylindrical Surface
4.5.2.5 Web Cutting by Sweeping Curves or Surfaces
4.5.2.6 Web Cutting using a Tool or Sheet Body
4.5.2.7 Web Cutting Options
4.5.3 Section Command
4.5.4 Separating Surfaces from Bodies
4.5.5 Separating Multi-Volume Bodies
2021.11

4.5 Geometry Decomposition

Geometry decomposition is often required to generate an all-hexahedral mesh for three-dimensional solids, as fully automatic all-hex mesh generation of arbitrary solids is not yet possible in Cubit. While geometry booleans can be used for decomposition (and are the basis of the underlying implementation of advanced decomposition tools described here), Cubit has a webcut capability specially tuned for decomposition. It is also useful to split periodic surfaces to facilitate quad and hex meshing.

4.5.1 Splitting Geometry

The Split command divides curves or surfaces into multiple entities. The command results are similar to imprinting. However, vertex and/or curve creation is not necessary for the split command.

4.5.1.1 Split Curve

The Split Curve command will split a curve without the need for geometry creation (unlike imprinting).

To split a curve

  1. On the Command Panel, click on Geometry and then Curve.

  2. Click on the Modify action button.

  3. Select Split from the drop-down menu.

  4. Enter the appropriate value for Curve ID. This can also be done using the Pick Widget function.

  5. Select Fraction, Vertex ID, By Location, Distance or Pick from the Split Method/Location menu.

  6. Click Apply.

Split Curve <id> [location on curve options] [Merge] [Preview]

To split a curve, simply specify a location or a location on curve (see location specification). Using the preview keyword will draw the splitting location on the curve. The merge keyword will merge any topology that contains the newly created vertex.

4.5.1.2 Split Periodic Surfaces

Solids which contain periodic surfaces include cylinders, torii and spheres. Splitting periodic surfaces can in some cases simplify meshing, and will result in curves and surfaces being added to the volume.

To split periodic surfaces

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Modify action button.

  3. Select Split Periodic from the drop-down menu.

  4. Enter the appropriate value for Volume ID(s). This can also be done using the Pick Widget function.

  5. Click Apply.

Split Periodic Body <id_range|all>

This command splits all periodic surfaces in a body or bodies.

4.5.1.3 Split Surface

The Split Surface command divides one or more surfaces into multiple surfaces. The command results are similar to imprint with curve. However, curve creation is not necessary for splitting surfaces. Three primary forms of the command are available.

The first form splits a single surface using locations while the second splits by extending a surface hard-line until it hits a surface boundary. The split automatic splits either a single surface or a chain of surfaces in an automatic fashion.

4.5.1.3.1 Split Across

Two forms of Split Across are available

  1. On the Command Panel, click on Geometry and then Surface.

  2. Click on the Modify action button.

  3. Select Split from the drop-down menu.

  4. Select By Location from the drop-down menu.

  5. Enter in the appropriate value for Surface ID(s). This can also be done using the Pick Widget function.

  6. Enter in the appropriate settings on this menu.

  7. Click Apply.

Split Surface <id> Across [Pair] Location <options multiple locs> [Preview [Create]]

Split Surface <id> Across Location <multiple locs> Onto Curve <id> [Preview] Create]]

This command splits a surface with a spline projection through multiple locations on the surface. See Location, Direction, and Axis Specification for a detailed description of the location specifier.Figure 136 shows a simple example of splitting a single surface into two surfaces.A temporary spline was created through the three specified locations (Vertex 5 6 7), and this curve was used to split the surface.

split surface 1 across location vertex 5 6 7

Figure 136: Splitting Across with Multiple Locations

The pair keyword will pair locations to create multiple surface splitting curves (each defined with two locations). An even number of input locations is required.Figure 137 shows an example:

split surface 1 across pair vertex 5 7 6 8

split_across_pair.gif

Figure 137: Splitting Across with Pair Option

The preview keyword will show a graphics preview of the splitting curve.If the create keywordis also specified, a free curve (or curves) will be created - these are the internal curves that are used to imprint the surfaces.

The onto curve format of the command takes one or more locations on one side of the surface and projects them onto a single curve on the other side of the surface.Figure 138 shows an example:

split surface 1 across vertex 5 6 onto curve 4

Figure 138: Splitting Across with Onto Curve

4.5.1.3.2 Split Extend

The Split Extend function can be called with the following command:

Split Surface <id_list> Extend [Vertex <id_list> | AUTO] [Preview [Create]]

With the following settings:

Set Split Surface Extend Normal {on|OFF}

Set Split Surface Extend Gap Threshold <val>

Set Split Surface Extend Tolerance<val>

This command splits a surface by extending a surface hard-line until it hits a surface boundary. Figure 139 shows a simple example of extending a curve. The hard-line curve was extended from the specified vertex until it hit the surface boundary.

split surface 1 extend vertex 2

Figure 139: Splitting by Extending Hard-line

The auto keyword will search for all hard-lines and extend them according to the Split Surface Extend settings. Figure 140 shows an example:

split surface 1 extend auto

Figure 140: Splitting by Extending with Auto Option

The preview keyword will show a graphics preview of the splitting curve. If the create keyword is also specified, a free curve (or curves) will be created - these are the internal curves that are used to imprint the surfaces.

The normal setting can be turned on or off. When it is on, Cubit will attempt to extend the hard-line so that it is normal to the curve it will intersect. An example of this is in Figure 141:

set split surface normal on
split surface 1 extend vertex 2

Figure 141: Splitting by Extending a Hard Line with Normal Setting ON

Cubit uses the gap threshold to decide whether or not to extend a hard-line when the user specifies auto. If the distance between a vertex on a hard-line and the curve it will hit is greater than the gap threshold, then Cubit will not extend that hard-line. The default value is INFINITY, and can be set to any value. To reset the value back to INFINITY, set the gap threshold to -1.0.

This setting only applies when using the keyword auto.

An example of using the gap threshold is shown in Figure 142:

set split surface gap threshold 2.0
split surface 1 extend auto

Figure 142: Extending Hard-lines with Gap Threshold = 2.0.
(Notice Vertex 1 was not extended because it exceeded the gap threshold)

The tolerance setting can be used to avoid creating short curves on the surface boundary. If Cubit tries to extend a hard-line that comes within tolerance of a vertex, it will instead snap the extension to the existing vertex. An example of this is shown in Figure 143:

set split surface tolerance 1.0
split surface 1 extend vertex 2

Figure 143: Extending Hard-lines with Tolerance
(Notice the extension snapped to Vertex 3)

4.5.1.3.3 Split (Automatically)

This form of the command splits a single surface or a chain of surfaces in an automatic fashion.It is most convenient for splitting a fillet or set of fillets down the middle - oftentimes necessary to prepare for mesh sweeping. These surfaces cannot have multiple curve loops.

To Split a surface

  1. On the Command Panel, click on Geometry and then Surface.

  2. Click on the Modify action button.

  3. Select Split from the drop-down menu.

  4. Select Along Fillet from the drop-down menu.

  5. Enter in the appropriate value for Surface ID(s). This can also be done using the Pick Widget function.

  6. Click Apply.

Split Surface <id_list>[Corner Vertex <id_list>] [Direction Curve <id>] [Segment|Fraction|Distance <val> [From Curve <id>]] [Through Vertex <id_list>] [Parametric <on|OFF>] [Tolerance <val>] [Preview [Create]]

The volume shown in Figure 144 was quickly prepared for sweeping by splitting the fillets and specifying sweep sources as shown (with the sweep target underneath the volume). The surface splits are shown in blue.

split_sweep_example.gif

Figure 144: Splitting Fillets to Facilitate Sweeping

Each surface is always split with a single curve along the length of the surface (or multiple single curves if the Segment option is used). The splitting curve will either be a spline, arc or straight line.

4.5.1.3.3.1 Logical Rectangle

The Split Surface command analyzes the selected surface or surface chain to find a logical rectangle, containing four logical sides and four logical corners; each side can be composed of zero, one or multiple curves. If a single surface is selected (with no options), the logical corners will be those closest to 90 and oriented such that the surface will be split parallel to the longest aspect ratio of the surface. If a chain of surfaces is selected, the logical corners will include the two corners closest to 90 on the starting surface of the chain and the two corners closest to 90 on the ending surface of the chain.

The split will always occur along the chain.

In Figure 1360, the logical corners selected by the algorithm are Vertices 1-2-5-6. Between these corner vertices the logical sides are defined; these sides are described in Table 1. The default split occurs from the center of Side 1 to the center of Side 3 (parallel to the longest aspect ratio of the surface), and is shown in blue.

Figure 145: Split Surface Logical Properties

Table 1. Listing of Logical Sides for Figure 1360

Logical Side

Corner Vertices

Curve Groups

1

1-2

1

2

2-5

2,3,4

3

5-6

5

4

6-1

6

Figure 1361 shows a surface along with 2 possibilities for its logical rectangle and the resultant splits.

Figure 146: Different Possible Logical Rectangles for Same Surface

Table 2 shows various surfaces and the resultant split based on the automatically detected or selected logical rectangle. Note that surfaces are always traversed in a counterclockwise direction.

Table 2 - Sample Surfaces and Logical Rectangles

Surface(s) (Resultant Split in Blue)

Ordered Corners (to form the logical rectangle)

corner1.gif

1-2-3-4

(using aspect ratio)

corner2.gif

4-1-2-3

(user selected)

corner3.gif

1-2-5-6

corner4.gif

2-5-6-1

corner5.gif

1-2-3-4

(split is always along the chain)

corner6.gif

1-2-3-4

(notice triangular surfaces along the chain)

corner7.gif

1-1-2-3

(note side 1 of the logical rectangle is collapsed; side 3 is from vertex 2 to 3)

corner8.gif

1-2-2-3

(note side 2 of the logical rectangle is collapsed)

corner9.gif

1-2-3-4

corner10.gif

1-2-4-4

corner11.gif

1-1-2-2

corner12.gif

1-1-2-2

(selected automatically)

4.5.1.3.3.2 Split Orientation

If a chain of surfaces are split, the surfaces will always be split along the chain. The command will not allow disconnected surfaces.

For a single surface, the split direction logic is a bit more complicated. If no options are specified, the surface aspect ratio determines the split direction - the surface will be split parallel to the longest aspect ratio side through the midpoint of each curve. This behavior can be overridden by the order the Corner vertices are selected (the split always starts on the side between the first two corners selected), the Direction option, the From Curve option, or the Through Vertex list.

Table 3 shows examples of the various split orientation methods. These options are explained in more detail in the sections below.

Table 3 - Split Orientation Methods

Surface Example

Split Orientation Method

orient1.gif

Multiple surfaces are always split along the chain

orient2.gif

Parallel to longest surface aspect ratio (default)

orient6.gif

Corner Vertex 4 1 2 3

(split always starts on side 1 of the logical rectangle)

orient3.gif

Direction Curve 1

orient4.gif

From Curve 1 Fraction .75

or

From Curve 1 Distance 7.5

orient5.gif

Through Vertex 5 6

4.5.1.3.3.3 Corner Specification

The corner option allows you to specify corners that form logical rectangle the algorithm uses to orient the split on the surface. When analyzing a surface to be split, the software automatically selects the corners that are closest to 90. The Preview option displays the automatically selected corners in red. Sometimes incorrect corners are chosen, so you must specify the desired corners yourself. The split always starts on the side between the first two corners selected and finishes on the side between the last two corners selected. Figure 1362 shows a situation where the user had to select corners to get the desired split.

Figure 147: Selecting the Desired Corners

The split can be directed to the tip of a triangular shaped surface by selecting that corner vertex twice (at the start or end of the corner list) when specifying corners, creating a zero-length side on the logical rectangle. A shortcut exists whereas if you specify only 3 corner vertices, the zero-length side will be directed to the first corner selected. If you specify only 2 corner vertices, a zero-length side will be directed to both the first and second corner you select. Table 4 shows these examples. Note the software will automatically detect triangle corners based on angle criteria - the corner selection methods for zero-length sides explained in this section need only be applied if the angles are outside of the thresholds specified in the Set Split Surface Auto Detect Triangle settings.

Table 4 - Selecting Corners to Split to Triangle Tips

Surface

Corner Specification

corner10.gif

1-2-4-4- or 4-4-1-2

or

4-1-2 (shortcut method)

corner11.gif

1-1-2-2 or 2-2-1-1

or

1-2 or 2-1 (shortcut method)

4.5.1.3.3.4 Direction

The direction option allows you to conveniently override the default split direction on a single surface. Simply specify a curve from the logical rectangle that is parallel to the desired split direction. If Corners are also specified, the Direction option will override the split orientation that would result from the specified corner order. The Direction option is not valid on a chain of surfaces. Figure 1363 shows an example.

Figure 148: Direction Specification Overrides Corner Order

4.5.1.3.3.5 Segment|Fraction|Distance

The segment option allows you to split a surface into 2 or more segments that are equally spaced across the surface. The fraction option allows you to override the default 0.5 fractional split location. The distance option allows you to specify the split location as an absolute distance rather than a fraction. By specifying a from curve, you can indicate which side of the logical rectangle to base the segment, fraction or distance from (versus a random result). Table 5 gives examples of these options.

Table 5 - Segment, Fraction, Distance Examples

Surface

Command Options

seg_frac_dist1.gif

Segment 6 From Curve 1

seg_frac_dist2.gif

Fraction .3 From Curve 1

seg_frac_dist3.gif

Distance 3 From Curve 1

4.5.1.3.3.6 Through Vertex

The through vertex option forces the split through vertices on surface boundaries perpendicularto the splitdirection.Use this option if the desired fraction is not constant from one end of the surface to another or if a split would otherwise pass very close to an existing curve end resulting in a short curve.Through vertices can be used in conjunction with the Fraction option- the split will linearly adjust to pass exactly through the specified vertices.It is not valid with the Segment option.The maximum number of Through Vertices that can be specified is equal to the number of surfaces being split plus one.The selected vertices can be free, but must lie on the perpendicular curves.Table 6 gives several examples. Table 6 - Through Vertex Examples

Surface(s)

Command Options

through1.gif

Fraction .3 From Curve 1 Through Vertex 9

through2.gif

Through Vertex 5 6 7 8

4.5.1.3.3.7 Parametric

By default, split locations are calculated in 3D space and projected to the surface. As an alternative, split locations can be calculated directly in the surface parametric space. In rare instances, this can result in a smoother or more desirable split. The command option parametric {on|off} can be used to split the given surfaces in parametric space. Alternatively, the default can be overridden with the Set Split Surface Parametric {on|OFF} command.

4.5.1.3.3.8 Tolerance

A single absolute tolerance value is used to determine the accuracy of the split curves. A smaller tolerance will force more points to be interpolated. The tolerance is also used when detecting an analytical curve (e.g., an arc or straight line) versus a spline. A looser tolerance will result in more analytical curves. The default tolerance is 1.0. The command option tolerance <val> can be used to split the given surfaces using the given tolerance. Alternatively, the default tolerance can be overridden with the Set Split Surface Tolerance <val> command.

It is recommended to use the largest tolerance possible to increase the number of analytical curves and reduce the number of points on splines, resulting in better performance and smaller file sizes. The Preview option displays the interpolated curve points. Table 7 shows the effect of the tolerance for a simple example.

Table 7 - Effect of Tolerance on Split Curve

Surface

Tolerance

tolerance1.gif

2.0

tolerance2.gif

1.0

tolerance3.gif

0.5

tolerance4.gif

0.01

4.5.1.3.3.9 Preview

The preview keyword will show a graphics preview (in blue) of the splitting curve (or curves) and the corner vertices (in red) selected for the logical rectangle. The curve preview includes the interpolated point locations that define spline curves. Note that if no points are shown on the interior of the curve, it means that the curve is an analytical curve (line or arc). If the create keyword is also specified, a free curve (or curves) will be created - these are the internal curves that are used to imprint the surfaces. Table 8 shows some examples.

Table 8 - Graphics Preview

Surface

Curve Type

preview1.gif

Spline

preview2.gif

Arc (no preview points shown on interior of curve)

4.5.1.3.3.10 Settings

This section describes the settings that are available for the automatic split surface command. To see the current values, you can enter the command set split surface, optionally followed by the setting of interest (without specifying a value).

Set Split Surface Tolerance <val>

This sets the default tolerance for the accuracy of the split curves. See the Tolerance section for more information.

Set Split Surface Parametric {on|OFF}

This sets the default for whether surfaces are split in 3D (default) or in parametric space.See the Parametric section for more information.

Set Split Surface Auto Detect Triangle {ON|off}

Set Split Surface Point Angle Threshold <val>

Set Split Surface Side Angle Threshold <val>

The split surface command automatically detects triangular shaped surfaces as explained in the section on Corners. This behavior can be turned off with the setting above. Two thresholds are used when detecting triangles - the point angle threshold and the side angle threshold, specified in degrees. Corners with an angle below the Point Angle threshold are considered for the tip of a triangle (or the collapsed side of the logical rectangle). Corners within the Side Angle threshold of 180 are considered for removal from the logical rectangle. In order for a triangle to actually be detected, corners for both the point and side criteria must be met. The default Point Angle threshold is 45, and the default Side Angle threshold is 27. Figure 1364 provides an illustration.

Figure 149: Triangle Detection Settings

4.5.1.3.4 Split Skew

The Split Skew function can be called with the following command:

Split Surface <id_list> Skew [Preview] [Create]

This command will split a surface or list of surfaces in a logical way to reduce the amount of skew in a quadrilateral mesh. This function uses the control skew algorithm to determine where to make these logical splits. Users should note that Split Skew can only be utilized effectively on surfaces that lend themselves to a structured meshing scheme. These surfaces cannot have multiple curve loops. Figure 1365 shows a simple example of a surface being split.

split surface 1 skew

Figure 150: Split Skew applied to an L-shaped surface

The preview keyword will show a graphics preview of the splitting curves. If the create keyword is also specified, free curves will be created.

4.5.2 Web Cutting

The term "web cutting" refers to the act of cutting an existing body or bodies, referred to as the "blank", into two or more pieces through the use of some form of cutting tool, or "tool". The two primary types of cutting tools available in Cubit are surfaces (either pre-existing surfaces in the model or infinite or semi-infinite surfaces defined for web cutting), or pre-existing bodies.

The various forms of the web cut command can be classified by the type of tool used for cutting. These forms are described below, starting with the simplest type of tool and progressing to more complex types.

4.5.2.1 General Notes

The primary purpose of web cutting is to make an existing model meshable with the hex meshing algorithms available in Cubit. While web cutting can also be used to build the initial geometric model, the implementation and command interface to web cutting have been designed to serve its primary purpose. Several important things to remember about web cutting are as follows:

The Decomposition Tutorials and the Power Tools Tutorial contain some examples that demonstrate the use of web cutting operations.

4.5.2.2 Web Cutting with an Arbitrary Surface

An arbitrary "sheet" surface can also be used to web cut a body. This sheet need not be planar, and can be bounded or infinite. The following commands are used:

To webcut using a sheet

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Surface Extended from the drop-down menu.

  4. Enter in the appropriate values for Body ID(s) and With Surface ID(s). This can also be done using the Pick Widget function.

  5. Click Apply.

Webcut {blank} with sheet {body|surface} <id> [webcut_options]

Webcut {blank} with sheet extended [from] surface <id> [webcut_options]

In its first form, the command uses a sheet body, either one that is pre-existing or one formed from a specified surface. Note that in this latter case the (bounded) surface should completely cut the body into two pieces. Sheet bodies can be formed from a single surface, but can also be the combination of many surfaces; this form of web cut can be used with quite complicated cutting surfaces.

Extended sheet surfaces can also be used; in this case, the specified surface will be extended in all directions possible. Note that some spline surfaces are limited in extent, and so these surfaces may or may not completely cut the blank.

4.5.2.3 Chop Command

The chop command works similarly to a web cut command, but is faster. Given two bodies, the command will find the intersection of the two bodies, and divide the main body into a body that lies outside the intersection, and a body that lies inside the intersection. The tool body will be deleted, unless the keep option is specified. The syntax of the command is:

Chop [Volume|BODY] <id> with [Volume|BODY] <id> [keep] [nonreg]

The nonreg option results in the bodies being non-regularized.

4.5.2.4 Web Cutting with a Planar or Cylindrical Surface

This section details the commands used to web cut with a planar or cylindrical surface.

4.5.2.4.1 Coordinate Plane

In the command’s simplest form, a coordinate plane can be used to cut the model, and can optionally be offset a positive or negative distance from its position at the origin.

To use a coordinate plane to webcut

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Coordinate Plane from the drop-down menu.

  4. Enter the appropriate values for Body ID(s). This can also be done using the Pick Widget tool.

  5. Select YZ, ZX or XY.

  6. Enter in the Offset Value.

  7. Enter any other appropriate settings from this menu.

  8. Click Apply.

Webcut {Volume|Body|Group} <id_range> [With] Plane {xplane|yplane|zplane} [Offset <val>] [rotate <theta> about x|y|z <xval> <yval> <zval> [center <xval> <yval> <zval>]] webcut_options

The cutting plane can be rotated about a user-specified axis using the rotate option. The center of rotation can be moved by using the center option.

4.5.2.4.2 Planar Surface

An existing planar surface can also be used to cut the model; in this case, the surface is identified by its ID as the cutting tool.

To use an existing planar surface to webcut

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select General Plane from the drop-down menu.

  4. Enter the appropriate values for Body ID(s). This can also be done using the Pick Widget tool.

  5. Enter the appropriate settings for With Plane. By clicking the With Plane... button, another window appears to specify settings.

  6. Enter any other appropriate settings from this menu.

  7. Click Apply.

Webcut {Volume|Body|Group} <id_range> [With] Plane Surface <surface_id> webcut_options

4.5.2.4.3 Plane from 3 Points

Any arbitrary planar surface can be used by specifying three vertices that define the plane, and can optionally be offset a positive or negative distance from this plane.

To use a planar surface by specifying three vertices

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Plane From Vertices from the drop-down menu.

  4. Enter the appropriate values for Body ID(s), Vertex 1 ID, Vertex 2 ID and Vertex 3 ID. This can also be done using the Pick Widget tool.

  5. Click Apply.

Webcut {Volume|Body|Group} <id_range> [With] Plane Vertex <vertex_1> [Vertex] <vertex_2> [Vertex] <vertex_3> [Offset <value>] webcut_options

The plane to be used for the web cut can be previewed with the preview option in the general webcut options.

4.5.2.4.4 Plane Normal to Curve

The next command allows a user to specify an infinite cutting plane by specifying a location on a curve. The cutting plane is created such that it is normal to the curve tangent at the specified location.

To specify the cutting plane by specifying the location on the curve

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Plane From Curve from the drop-down menu.

  4. Enter the appropriate values for Body ID(s) and Curve ID. This can also be done using the Pick Widget tool.

  5. Select Fraction, Position, Distance or Near Vertex from the Position menu.

  6. Enter any other appropriate settings from this menu.

  7. Click Apply.

Webcut {Volume|Body|Group} <id_range> [With] Plane Normal To Curve <curve_id>
{Position <xval><yval><zval> | Close_To Vertex <vertex_id>} webcut_options

Webcut {Volume|Body|Group} <id_range> [With] Plane Normal To Curve <curve_id>
{Fraction <f> | Distance <d>} [[From] Vertex <vertex_id>] webcut_options

The position on the curve can be specified as:

  1. A fraction along the curve from the start of the curve, or optionally, from a specified vertex on the curve.

  2. A distance along the curve from the start of the curve, or optionally, from a specified vertex on the curve.

  3. An xyz position that is moved to the closest point on the given curve.

  4. The position of a vertex that is moved to the closest point on the given curve.

The point on the curve can be previewed with the Draw Location On Curve command and the plane to be used for the web cut can be previewed with the preview option in the general webcut options.

4.5.2.4.5  General Plane Specification

A webcut plane can be defined using the general plane specification options in the Specifying a Plane section of the documentation.

To webcut using general plane specification

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select General Plane from the drop-down menu.

  4. Enter the appropriate values for Body ID(s). This can also be done using the Pick Widget tool.

  5. Enter the appropriate settings for With Plane. Click on the With Plane... button, another window appears to specify settings.

  6. Enter any other appropriate settings from this menu.

  7. Click Apply.

Webcut {Volume|Body|Group} <id_range> [With] General Plane {options} webcut_options

4.5.2.4.6  Cylindrical Surface

Finally, a semi-infinite cylindrical surface can be used by specifying the cylinder radius, and the cylinder axis. The axis is specified as a line corresponding to a coordinate axis, the normal to a specified surface, two arbitrary points, or an arbitrary point and the origin. The "center" point through which the cylinder axis passes can also be specified.

To use a cylindrical surface to webcut

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Cylinder from the drop-down menu.

  4. Enter the appropriate values for Body ID(s). This can also be done using the Pick Widget tool.

  5. Select Value or From Existing Arc from the Radius menu.

  6. Enter in the appropriate values for Radius or Arc ID.

  7. Select X Axis, Y Axis, Z Axis, Vector, Vertex Pair or Surface Normal from the Axis menu.Enter any other appropriate settings from this menu.

  8. Click Apply.

Webcut {Volume|Body|Group} <range> [With] Cylinder Radius <val> Axis {x|y|z|normal of surface <id>| vertex <id_1> vertex <id_2>| <x_val> <y_val> <z_val>>} [center <x_val> <y_val> <z_val>] webcut_options

4.5.2.4.7 Cone Surface

A semi-infinite cone surface can be used by specifying the cone outer radius, and the cone inner radius. The axis is specified as a location first of where the outer radius is applied and the second location of where the inner radius is applied.

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Cone from the drop-down menu.

  4. Enter the appropriate values for Body ID(s). This can also be done using the Pick Widget tool.

  5. Enter the appropriate values for Radius 1 and Radius 2.

  6. Enter the appropriate settings for Location 1 and Location 2. Click on the Location... button, another window appears to specify settings.

  7. Enter any other appropriate settings from this menu.

  8. Click Apply.

Webcut {Volume|Body|Group} <ids> [With] cone radius <val> <val> location {options} location {options} [Imprint] [Merge] [group_results] [preview]

4.5.2.5 Web Cutting by Sweeping Curves or Surfaces

Webcutting with sweeping creates a swept tool body in the same step as the web cut operation. There are 4 general ways to web cut.

4.5.2.5.1 Web Cutting by Sweeping a Surface Along a Trajectory

This command allows one or more surfaces to be swept, creating a volume that is used for the web cut. If more than one surface is specified, the surfaces must contain coincident curves. The surfaces are swept along a direction and some distance or perpendicular and some distance or along a curve. For best results the curve to sweep the surface along should intersect one of the surfaces. The through_all option will sweep the surfaces along the trajectory far enough so as to intersect all input bodies. The stop surface <id> option is used to identify a surface at which the sweep will stop. If using this option when sweeping along a curve, the sweep will stop at the first place possible. The up_to_next option indicates that the user wants to web cut with only the first water tight volume that forms as a result of the intersection between sweep and union of all blank bodies. The [outward|inward] options specify a sweeping direction that is either INTO the volume or OUT from the volume.

To sweep a surfvace along a curve or vector

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Sweep Surface from the drop-down menu.

  4. Enter in the appropriate values for Body ID(s) and Surface ID. This can also be done using the Pick Widget function.

  5. Select Vector or Along Curve from the Direction menu.

  6. Enter in the appropriate settings from this menu.

  7. Click Apply.

Webcut {Volume|Body|Group} <range> Sweep Surface <id_range> {Vector <x> <y> <z> [Distance <distance>] | Along Curve <id>} [Through_all | Stop Surface <id> | Up_to_next ] [webcut_options]

To sweep a surface a perpendicular direction

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Sweep Surface from the drop-down menu.

  4. Enter in the appropriate values for Body ID(s) and Surface ID. This can also be done using the Pick Widget function.

  5. Select Perpendicular from the Direction menu.

  6. Enter in the appropriate settings from this menu.

  7. Click Apply.

Webcut {Volume|Body|Group} <id> Sweep Surface <id_range> Perpendicular {Distance <distance> | Through_all | Stop Surface <id>} [OUTWARD|Inward] [webcut_options]

Figure 151: Example of web cutting with swept surfaces in a direction (left) and result web cut (right)

Figure 152: Example of web cutting along a curve to a stop surface (left) and result web cut (right)

4.5.2.5.2 Web Cutting by Sweeping a Surface About an Axis

This command allows one or more surfaces to be swept, creating a volume that is used for the web cut. If more than one surface is specified, the surfaces must contain coincident curves. The surface is swept about a user-defined axis or about one of the x y z coordinate axes and a specified angle. The stop surface <id> option is used to identify a surface at which the sweep will stop. The up_to_next option indicates that the user wants to web cut with only the first water tight volume that forms as a result of the intersection between sweep and union of all blank bodies. For these 2 options to work correctly the user must specify an angle large enough for the rotation to traverse the stop surface or the up_to_next surface.

To sweep a surface by rotating about an axis

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Sweep Surface from the drop-down menu.

  4. Enter in the appropriate values for Body ID(s) and Surface ID. This can also be done using the Pick Widget function.

  5. Select Rotate About Axis from the Direction menu.

  6. Enter in the appropriate settings from this menu.

  7. Click Apply.

Webcut {Volume|Body|Group} <id> Sweep Surface <id_range> {Axis <xpoint ypoint zpoint xvector yvector zvector> | Xaxis | Yaxis | Zaxis } Angle <degrees> [Stop Surface <id> | Up_to_next] [webcut_options]

4.5.2.5.3 Web Cutting by Sweeping a Curve(s) Along a Trajectory

This command allows a curve(s) to be swept, creating a surface that is used for the web cut. If multiple curves are specified, they must share vertices and form a continuous path. The curve(s) is swept along a direction and some distance or along another curve. If sweeping a curve(s) along another curve, for best results the curve(s)-to-swept and the curve to sweep along should intersect at some point. The stop surface <id> option is used to identify a surface at which the sweep will stop. If using this option when sweeping along a curve, the sweep will stop at the first place possible. The through_all option will sweep the curve(s) along the trajectory far enough so as to intersect all input bodies. For the web cut to be successful, the swept curve(s) must completely traverse a portion of a blank body(s), cutting off a complete piece of the blank body(s). Option through_all should not be used when defining the web cut with a vector and a distance or along a curve.

To sweep a curve along a curve or vector

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Sweep Curve from the drop-down menu.

  4. Enter in the appropriate values for Body ID(s) and Curve ID. This can also be done using the Pick Widget function.

  5. Select Vector or Along Curve from the Direction menu.

  6. Enter in the appropriate settings from this menu.

  7. Click Apply.

Webcut {Volume|Body|Group} <id> Sweep Curve <id_range> {Vector <x> <y> <z> [Distance <distance>| Along curve <id>] } [Through_all | Stop Surface <id>] [webcut_options]

4.5.2.5.4 Web Cutting by Sweeping a Curve(s) About an Axis

This command allows a curve to be swept, creating a surface that is used for the web cut. If multiple curves are specified, they must share vertices and form a continuous path. The curve(s) is swept about a user-defined axis or about one of the x y z coordinate axes and a specified angle. For the web cut to be successful, the swept curve(s) must completely traverse a portion of a blank body(s), cutting off a complete piece of the blank body(s). The stop surface <id> option is used to identify a surface at which the sweep will stop. For this option to work correctly the user must specify an angle large enough for the rotation to traverse the stop surface.

To sweep a curve about an axis

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Sweep Curve from the drop-down menu.

  4. Enter in the appropriate values for Body ID(s) and Curve ID. This can also be done using the Pick Widget function.

  5. Select Rotate About Axis from the Direction menu.

  6. Enter in the appropriate settings from this menu.

  7. Click Apply.

Webcut {Volume|Body|Group} <id> Sweep Curve <id_range> {Axis <xpoint ypoint zpoint xvector yvector zvector> | Xaxis | Yaxis | Zaxis } Angle <degrees> [Stop Surface <id>] [webcut_options]

4.5.2.6 Web Cutting using a Tool or Sheet Body

Any existing body in the geometric model can be used to cut other bodies; the command to do this is:

To use an existing body to webcut

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Tool from the drop-down menu.

  4. Enter the appropriate values for Body ID(s). This can also be done using the Pick Widget function.

  5. Click Apply.

Webcut {blank} tool [body] <id> [webcut_options]

This simply uses the specified tool body in a set of boolean operations to split the blank into two or more pieces.

Another form of the command cuts the body list with a temporary sheet body formed from the curve loop. This is the same sheet as would be created from the command Create Surface Curve <id_list>.

To webcut with the body formed from the curve loop

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Webcut action button.

  3. Select Loop from the drop-down menu.

  4. Enter the appropriate values for Body ID(s) and With Curve ID(s). This can also be done using the Pick Widget function.

  5. Click Apply.

Webcut {Body|Group} <id_range> [With] Loop [Curve] <id_range> NOIMPRINT|Imprint] [NOMERGE|Merge] [group_results]

Webcut {Volume|Body|Group} <id_range> [With] Bounding Box {Body|Volume|Surface|Curve|Vertex <id_range>} [Tight] [[Extended] {Percentage|Absolute} <val>] [{X|Width} <val>] [{Y|Height} <val>] [{Z|Depth} <val>]] NOIMPRINT|Imprint] [NOMERGE|Merge] [group_results]

The final form of this command cuts a body with the bounding box of another entity. This bounding box may be tight or extended.

bounding.gif

Figure 153: Cylinder cut with bounding box of prism.

4.5.2.7 Web Cutting Options

The following options can be used with all web cut commands:

[NOIMPRINT|imprint [include_neighbors] ]: In its default implementation, web cutting results in the pieces not being imprinted on one another; this option forces the code to imprint the pieces after web cutting. The include_neighbors option will also imprint adjacent bodies.

[NOMERGE|merge]: By default, the pieces resulting from an imprint are manifold; specifying this option results in a merge check for all surfaces in the pieces resulting from the web cut.

[group_results]: The various pieces resulting from the previous command are placed into a group named ‘webcut_group’.

[preview]: This option will preview the web cutting plane without executing the command.

4.5.3 Section Command

This command will cut a body or group of bodies with a plane, keeping geometry on one side of the plane and discarding the rest. The syntax for this command is:

Section {Body|Group} <id_range> [With] {Xplane|Yplane|Zplane} [Offset <value>] [NORMAL|Reverse] [Keep]

Section {Body|Group} <id_range> With Surface <id> [NORMAL|Reverse] [Keep]

In the first form, the specified coordinate plane is used to cut the specified bodies. The offset option is used to specify an offset from the coordinate plane. In the second form, an existing (planar) surface is used to section the model. In either case, the reverse keyword results in discarding the positive side of the specified plane or surface instead of the other side. The keep option results in keeping both sides; the section command used with this option is equivalent to webcutting with a plane.

4.5.4 Separating Surfaces from Bodies

The separate surface command is used to separate a surface from a sheet body or a solid body.

To separate a surface from a body

  1. On the Command Panel, click on Geometry and then Surface.

  2. Click on the Modify action button.

  3. Select Split from the drop-down menu.

  4. Select Separate from the drop-down menu.

  5. Enter in the appropriate value for Surface ID(s). This can also be done using the Pick Widget function.

  6. Click Apply.

Separate Surface <range>

Separating a surface from a solid body will create a "hole" in the solid body. Thus the solid body will become a sheet body. The newly separated surface will be also sheet body, but it will have a different id. Multiple surfaces can be separated from a body at the same time, but each separated surface will result in a distinct sheet body, as if the command had been performed on each surface individually.

4.5.5 Separating Multi-Volume Bodies

The separate command is used to separate a body with multiple volumes into a multiple bodies with single volumes.

To separate a body

  1. On the Command Panel, click on Geometry and then Volume.

  2. Click on the Modify action button.

  3. Select Separate from the drop-down menu.

  4. Enter in the appropriate value for Volume ID(s). This can also be done using the Pick Widget function.

  5. Click Apply.

Separate {Body|Volume} <id_range|all>

Only very rarely will this command be needed. It is provided for the occasional instance that a multi-volume body is found.

Another related command allows the user to control the separation of bodies after webcutting. In most instances the user will want to separate bodies after webcutting. One reason to possibly have this option turned off is to be able to keep track of all the volumes during a webcut. Setting this option to "off" keeps all volumes in the same body. But the more common approach is to name the original body and allow naming to keep track of volumes. This setting is on by default. The syntax is:

Set Separate After Webcut [ON|Off]