Modeling Modify geometry Use boolean operations on shells > What if...?

Edit objects

How to delete, convert, reverse, or change the internal structure of curves and surfaces.

Delete objects

Use the items in the Delete menu to remove objects, animation, and other information from the scene.

Delete the picked objects

Press .

or

Choose Delete > Delete active .

Delete all objects of a specific type in the scene

Use the other items in the Delete menu to quickly delete all objects of a specific type:
Delete > Delete guidelines
Delete > Painting > Delete Canvases  
Delete > Delete all locators

These items delete active and inactive, visible and invisible objects.

Delete a selection handle

Pick the selection handle (using Animation > Pick > Selection handle ) or its target object.
Choose Delete > Animation > Delete selection handles .
Set Objects to Active.
Click Go.

Delete all selection handles

Choose Delete > Animation > Delete selection handles .
Set Objects to All.
Click Go.

Change the tangent direction at a blend point

Control how a blend point changes the shape of its blend curve.

Change the tangent direction at a blend point

Choose Curves > Blend curve toolbox to show an extra floating palette containing the BlendCrv Tools tab.
Choose BlendCrv Tools > Blend curve edit .
Click the blend point you want to edit.
Use the tangent manipulator to set the tangent direction at the picked blend points.

Hold and click to select multiple blend points. Changes to the tangent direction manipulator are applied to all the selected blend points.

How do I use the tangent direction manipulator?

To set the tangent direction, click an axis line.

For direction constraints, the axis lines relate to world space (X, Y, Z). For geometry constraints, the axis lines relate to the curve, surface, or point cloud (U, V, Normal).





To change the rotation freely, click the rotation handle (the small circle on the arrow), then drag with the different mouse buttons or type rotational coordinates.
To change the rotation in a plane, click an arc, then drag left and right or type a rotation angle.





To change the tangent magnitude, click the square, then drag left or right or type a value.





To change the curvature magnitude, click the large circle, then drag left or right or type a value. The default is 1.0.

This handle appears when the constraint's continuity is set to G2 or higher.





To change the curvature rate of change, click the small circle, then drag left or right or type a value. The default is 1.0.

This handle appears when the constraint's continuity is set to G3 or higher.

Related topics

See Blend curves

Change the direction type of a blend curve constraint

Change the way a constraint affects the direction of the curve as it passes through the constraint.

Change the type of the picked blend points

Choose Curves > Blend curv toolbox to show an extra floating palette containing the BlendCrv Tools tab.

Do one of the following:
To constrain the curve to pass through the blend points position (without regard to direction), choose BlendCrv Tools > Constraint Interpolation Direction > Blend constraint interp location.
To constrain the curve to pass through the blend point in a certain world space direction, choose BlendCrv Tools > Constraint Interpolation Direction > Blend constraint interp direction.
To constrain the curve to pass through the blend point in a direction relative to the object to which it is attached, choose BlendCrv Tools > Constraint Interpolation Direction > Blend constraint interp geometry.

You can only change a constraint to "geometry" if it is already attached to an object.

Change the type of a directional constraint

Do one of the following:
To set the actual direction of the tangent at this point, choose BlendCrv Tools > Constraint Direction Type > Blend constraint directed.
To set the tangent at this point along a line (in either direction), choose BlendCrv Tools > Constraint Direction Type > Blend constraint parallel.

Related topics

See Blend curves

Change the continuity at a blend point

Change what kind of continuity a blend curve maintains with an object its constraint is attached to.

Change the continuity at the picked blend points

Choose Curves > Blend curve toolbox to show an extra floating palette containing the BlendCrv Tools tab.
Choose the continuity level from the BlendCrv Tools > Constraint Continuity sub-menu.

Change how curvature continuity is calculated at the picked blend point

You can only change the curvature type of a constraint that is attached to an object, and has G2 or greater continuity.

Choose the curvature type from the BlendCrv Tools > Curvature Type sub-menu:

What is the difference between parametric and geometric curvature?

Parametric curvature: align the curvature to the isoparametric direction of the surface. This type of curvature is especially useful to achieve curvature continuity with the corner of a surface.

Geometric curvature: align the curvature to the intersection of the tangent and the normal direction of the surface.

You must use geometric curvature if you want the blend curve to be planar (all points on the curve lie in the same plane).

Change the degree or parameterization of a blend curve

Change the degree of a blend curve, or change the parameterization of the underlying curve.

Change the degree of the picked blend curves

Choose Curves > Blend curv toolbox to show an extra floating palette containing the BlendCrv Tools tab.
Choose the degree from the BlendCrv Tools > Curve Degree sub-menu.

When you change the degree of a blend curve, surfaces constructed from the blend curve are also rebuilt to the new degree (unless they have constraints of their own that prevent regeneration).

Change the parameterization of the picked blend curves

Choose the parameterization from the BlendCrv Tools > Curve Knot Spacing sub-menu.

What if...?

] I want all new blend curves to have a certain degree or parameterization?

Choose BlendCrv Tools > Blend curve create   and set the degree and parameterization options.

Insert additional edit points/isoparametric curves into a curve or surface

Inserts edit points to a curve, or edit point isoparametric curves to a surface. This results in additional spans/patches and accompanying CVs.

Insert an edit point/isoparametric curve

Choose Object edit > Insert .
Click the curve or surface.

For surfaces, click the type of isoparametric curve (U or V) you want to insert.

Drag the locator to the position at which you want to insert.

Press and click to snap to the halfway (in parametric distance) points between edit points/isoparametric curves.

Click Go.

Slice (section) a group of curves

Use a curve to specify points to trim, detach, or insert on a group of curves or curves-on-surface all at once.

The Curve section tool lets you:

Define points on a group of curves at:
Intersections with a free curve, surface, reference plane or construction plane.
Specific parameters.
Specific distances from their endpoints.
Then use these points to do one of the following:
Trim the curves.
Detach the curves.
Insert edit points.
Create a curve that passes through the intersections.

Slice a group of curves at their intersections with a sectioning curve or surface

Choose Curve Edit > Curve section .
Do one of the following:
To trim the curves, set the Sectioning Mode to Trim.
To detach the curves, set the Sectioning Mode to Segment.
To insert edit points on the curves, set the Sectioning Mode to Slice and the Slice Creation Mode to Insert Edit Points.
To create a new curve that passes through the intersections, set the Sectioning Mode to Slice and the Slice Creation Mode to Create Curve.
Set the Sectioning Criterion to Geometry, then click Go.
Pick the curves or curves-on-surface you want to trim, in the view window where the curves and the sectioning curve/surface intersect.

For trims, click the part of the curve you want to keep. Red arrows show the "kept" part of the curve.

Click Go.
Click the curve, surface, or construction plane that you want to section with.

Section a group of curves based on parameter or distance

Choose Curve Edit > Curve section .
Do one of the following:
To trim the curves, set the Sectioning Mode to Trim.
To detach the curves, set the Sectioning Mode to Segment.
To insert edit points on the curves, set the Sectioning Mode to Slice and the Slice Creation Mode to Insert Edit Points.
To create a new curve that passes through the intersections, set the Sectioning Mode to Slice and the Slice Creation Mode to Create Curve.
Set the Sectioning Criterion:
To section each curve at a specific parameter, set the criterion to Point.
To section each curve at a specific length, set the criterion to Distance.
Click Go.
Pick the curves or curves-on-surface you want to trim.

For trims, click the part of the curve you want to keep. Red arrows show the "kept" part of the curve.

Green locators show the current sectioning point for each curve.

Do any of the following:
Drag the green locators to change the sectioning point on a curve, or click a locator and type an exact value.
Click a locator to see the corresponding parameter/distance on the prompt line.
Click Go.

After the Trim/Segment/Slice operation, locators reappear on each curve segment. Drag them to another location if you want to continue sectioning, or choose another tool.

What if...?

] Curves that should slice don't, or vice versa?

If you pick the curves to section in an orthographic windows, the intersections are visual. That is, where the curves appear to cross in the view window.
Remember to pick the curves in the orthographic view where they cross the sectioning curve or surface.
If you pick the curves to section in a perspective window, the intersections are exact. The curves must actually intersect the sectioning curve or surface in space.

Change an object's degree or number of spans

Use the Degree and Spans options in the control panel to quickly change the degree of or number of spans in the picked curves and surfaces.

Change an object's degree or number of spans

Pick the object.
Edit the Degree or Spans fields in the control panel.



AliasStudio shows the object with the new settings. This lets you check the effect of the change on existing evaluation locators.

Do any of the following:
Click Deviation to show the deviation between the changed and the original object in the prompt line.
Click Accept to use the changed object.
Click Cancel to return to the original object.

Simplify objects

Remove multi-knots from a curve or surface, or attempt to rebuild a curve or surface so it has the same shape but fewer spans/patches.

Simplify objects

Choose Curve Edit > Rebuild curve or Surface Edit > Rebuild surface .
Set Rebuild Type to Reduce Spans and turn Auto Recalc on.
Click the curves or surfaces.



Click Go.



Use the Tolerance control to adjust how much the tool can simply the curves.

A low value creates a more exact copy but simplifies the curve less. A high value is less exact but simplifies more.

If you click an isoparametric curve or trim edge with the Rebuild curve tool, it will be rebuilt into a curve on surface. You can only rebuild these curves as degree 1 or 3 curves.

Remove multi-knots

Choose Curve Edit > Rebuild curve or Surface Edit > Rebuild surface .
In the Rebuild Type pop-up menu, choose Del Multi-Knots.
Click the curves or surfaces.
Click Go.

Convert rational to non-rational geometry

Convert rational objects to non-rational objects. Rational geometry can be more accurate but is harder to work with and is unusable by many other software packages.

Convert rational objects to non-rational

Choose Curve Edit > Rebuild curve .
In the Rebuild Type pop-up menu, choose Non-rational.
Click the rational curves or surfaces.
Click Go.
Use the Tolerance and Continuity Angle controls to adjust how close the new object must come to the shape of the original.

A low value creates a more exact copy but with more complex geometry. A high value is less exact but creates simpler geometry.

Reverse the direction of a curve or surface

Reverse the tangent direction of a curve (by swapping the start and end points), or the parametric directions (U/V) of a surface.

Reverse, swap, or examine the directions (tangents) of a surface

If you want to reverse the direction of several surfaces at once, select them now.
Choose Surface Edit > Reverse Surface UV
In the option box, choose whether you want to reverse the U direction, the V direction, or swap U and V.
Click on the first surface you want to examine or reverse.

An indicator appears on the surface showing the current tangent(s) (U, V, or both, depending on the option chosen).

Do any of the following:
Click the and drag over the surface to examine the tangent direction(s).
Click the or the Reverse Active button in the window to reverse the surface you clicked.
Click the or the Reverse All button in the window to reverse all selected surfaces.
Click on another surface and repeat step 5.

Reversing the direction of the U and V parameters on a surface does not affect the direction of the normal.

Reverse the direction of a curve

Choose Curve Edit > Reverse Curve .
Click the first curve you want to reverse.

The tangent of the curve is shown at the point where you clicked.

Do any of the following:
Click the and drag along the curve to examine the tangent direction.
Click the or the Reverse Active button in the window to reverse the curve you clicked.
Click the or the Reverse All button in the window to reverse all selected curves.
Click on another curve to add to the selection and repeat step 3.

You can also select all the curves you want to reverse before entering the tool.

Reverse the direction of a surface normal

Reverse the direction of the normal on a surface

Choose Surface Edit > Orientation > Reverse Surface Orientation
Click a surface on which you want to reverse the normal.

An indicator appears on the object to show the current normal.

A light blue arrow means the normal is pointing toward you.
A yellow arrow means the normal is pointing away from you.
Do any of the following:
Click Reverse Active to reverse the last surface you clicked.
Click Reverse All to reverse all selected surfaces.

Reversing the direction of the normal on a surface does not affect the direction of the U or V parameters.

Construction history is preserved.

Orient surface normals

Orient surface normals so they point toward or away from the camera.

To change the direction normals face

Choose Surface Edit > Orientation > Set Surface Orientation .

All surfaces in the scene are shaded in blue and yellow.



Normals that point toward the camera result in blue surfaces; normals pointing away from the camera produce yellow surfaces.

To change the direction of the normal on a surface:
click the surface with the to orient the normal toward the camera.
click the surface with the (or + ) to orient the normal away from the camera.

You can click anywhere on the surface (not only the wireframe).

The color of the surface changes immediately.

If there are several surfaces to change, draw a pick-box around them (using the appropriate mouse button as described above).



After orienting all the normals to face toward the camera, all the surfaces in the scene should be blue.

Make all normals consistent

Modifies a collection of patches so that all normals accross a set of adjacent surfaces point in the same direction.

This helps to ensure that lighting is correct in renderings, and is also useful when modeling, and offsetting surfaces.

See Normals

To unify the normal direction on a collection of surfaces

Choose Surface Edit > Orientation > Unify Surface Orientation .

You are prompted to:

Select input surfaces. When finished, click `Classify'. 

Pick all the surfaces to be unified, and then click the Classify button in the lower right corner of the active window.

Based on the Topology Distance tolerance value (set in Preferences > Construction options , under the Tolerances: Topology sub-tab), the surfaces are grouped into sets of adjacent patches. Each set consists of those surface patches that are within the Topology Distance tolerance. The sets are drawn in different colors to help differentiate them.

An arrow shows the direction of the unified surface normal on each set. To change the direction of the surface normal, click on it.

When all surface normals are pointing in the correct direction, click the Unify button.

You can continue changing normal directions, then clicking Unify again, until you select another tool.

Construction history is preserved during this operation.

Unify Surface Orientation is a continuous function. To finish using this tool, select another tool.

Make an object open or closed

Converts an object between being open (having free endpoints or edges) and being closed (having connected endpoints/edges).

When a curve is closed, it forms a continuous loop, with no loose ends. When a curve is open it has two ends that can be moved independently, though they might happen to occupy the same point in space.

Similarly, a surface can be closed (periodic) across U, V, or both dimensions. When a surface is open, it has free edges.

Open or close a curve

Choose Object edit > Close .
Click the curve.

Open or close a surface

Choose Object edit > Close .
Click a U or V isoparametric curve or edge to open or close the surface across that dimension.

Close a curve or surface by attaching its ends/edges

Choose Object edit > Attach > Attach .
Click the two ends of a curve, or click opposite edges of a surface.

You must have at least four spans (not counting multi-knots) between the opposite edges of the surface to attach them.

What if...?

] I want to know if an object is open or closed?

1. Pick the object.

2. Choose Windows > Information > Information window .

3. The Geometry info section tells whether the object is open or closed.

Automatically add spans to a curve with high curvature

Automatically adds spans to the high curvature parts of a curve, resulting in more CVs in those areas and so easier control of the curve's shape.

Add edit points to a curve based on its curvature

Choose Curve Edit > Rebuild curve .
In the Rebuild Curve window:
In the Rebuild Type pop-up menu, choose Curvature.
Turn Auto Recalc on.

Set Max Spans Type to Absolute if you don't want the number of spans to exceed a certain number (Max Spans), otherwise use Relative.

Click the curve(s).



Click Go.



Use the Tolerance control to adjust how many edit points the tool should add to the curves. A low value inserts more new edit points. A high value adds fewer new edit points.

Convert a curve to uniform parameterization

Once converted, curves can be used with other tools.

Convert a curve to uniform parameterization

Choose Curve Edit > Rebuild curve .
In the Rebuild Curve window:
In the Rebuild Type pop-up menu, choose Uniform Knots.
Turn Auto Recalc on.
Click the curve(s).
Click Go.

Convert surfaces to and from shells (stitch/unstitch)

Surfaces can be altered for use in Boolean operations or for exportation to a CAD package.

Convert surfaces into a shell object

Make sure the normals on the surfaces are all pointing outward.
See Orient surface normals
Pick the surfaces you want to combine into a shell. The surfaces must together define a closed space with no gaps.
Choose Surface Edit > Stitch > Shell stitch .

The prompt line provides feedback on the result of the operation. For example: "Created 2 shells with 0 boundaries (0 non-manifold)."

If some boundaries are left open, small red arrows point to them.

Depending on how you set the options, a shell may not match the original surfaces exactly. In this case, unstitching will not produce surfaces that match the originals exactly either.

Convert a shell object into its separate surfaces

Pick the shell object.
Choose Surface Edit > Stitch > Shell unstitch .

What if...?

] I can't make a shell object because of gaps between the surfaces?

You can use the Align tool to make the surface edges match exactly.
v See Align curves and surfaces with continuity
You can change the tolerance governing how close surface edges must be. In the option box, turn off Use construction options and set the Tolerance value.

] I can't stitch surfaces together again after scaling them?

If you stitch an object, then scale it, then unstitch it, you may not be able to re-stitch the object. This is because the scaling operation can increase the gaps between surfaces beyond the current tolerances.

Use boolean operations on shells

Boolean operations applicable to shells are subtraction, intersection, and combination.

Subtract the volume of one shell from another

Choose Surface Edit > Shells > Shell subtract .
Click the shell the will be subtracted from.
Click the shell whose volume will be subtracted from the first shell.

Delete all but the intersecting volume between two shells

Choose Surface Edit > Shells > Shell intersect .
Click the two shells whose intersecting volume you want to keep.

Combine the volumes of two shells

Choose Surface Edit > Shells > Shell union .
Click the two shells whose volume you want to combine.

What if...?

] A boolean operation does not work?

Make sure the shell's normals are pointing outward.
See Reverse the direction of a curve or surface
Boolean operations may not work on shells that contain problematic geometry such as collapsed sides or multi-knots.
See Simplify objects
Boolean operations may not work on shells that have open edges. Use Object edit > Query edit to check for open edges. If CLOSED VOLUME is True, there are no open edges. Otherwise, the number of open edges is given, and they are clearly indicated by red arrows.

] I want to work with multiple shells at once?

Group the shells and perform the boolean operations on the groups.

See Group and ungroup objects