Creating Shapes in the Shape Modeling Construction Modes

Creating Shapes in the Shape Modeling Construction Modes

When you’re creating shapes, you can use any number of deformation operators, including envelopes, as the tools for sculpting the shapes. Because you can use these deformation operators for tasks other than shape animation, you need to let XSI know how you want to use them. For example, when you apply a deformation, you could be building the object’s basic geometry (modeling), or creating a shape key for use with shape animation (shape authoring), or creating an animated deformation effect (animation).

To tell XSI how you’re using the deformation, you need to select the correct construction mode: Modeling, Shape Modeling, Animation, or Secondary Shape. The mode puts the deformation operator in one of four regions in the object’s construction history that corresponds to that mode. These regions keep the construction history clean and well ordered by allowing you to classify operators according to how you want to use them.

For general information on all construction modes and the viewing options related to these modes, see Construction Modes and Regions in the Modeling and Deformation Basics guide.

Overview of Using the Construction Modes for Shape Animation

Here is a quick overview of how you can use the four different construction modes for doing shape animation:

Shape Animation and the Modeling Region

Because shapes are stored as offsets from the geometry, XSI needs to know which of the deformations are meant to be stored in a shape. The state of the geometry in the Modeling region of the construction history is the reference that the shape animation uses; that is, the resulting geometry of all the operators in the Modeling region is the base from which all shapes are created.

This means that when you make a change to the geometry in Modeling mode, any shape keys created from it are updated to reflect these changes.

In versions of XSI previous to v4.0, the first shape to be stored was the reference shape. All subsequent shape keys were stored as the difference in point positions from this reference. The “reference” shape is now the results of the operators that are in the Modeling region. If you want to change this reference, switch to Modeling mode to change the underlying geometry.

Switching between Construction Modes

Making changes to a shape-animated object is easy as long as you remember to switch to the appropriate mode. For example, let’s say that the director of the animation stops by your office and asks for changes to the geometry of the character. You assume that those changes would need to be propagated throughout the shapes you’ve already created. Since the modifications to be made are of a modeling nature, all you need to do is change the construction mode to Modeling and make the changes. When you change the geometry of the object in Modeling mode, these changes ripple down throughout the existing shape animation. Then you can switch back to Shape Modeling mode to continue creating shapes with this new geometry.

If you like, you can also have XSI switch construction modes automatically when you are performing certain operations. For example, when you save or store a shape key, XSI can automatically switch to Shape Modeling mode.

To change construction mode automatically

1. Choose File > Preferences from the main menu.

2. Select Modeling in the Preferences property editor and select the Construction Mode Auto Update option.

If you don’t want XSI to switch automatically, warning messages appear if you try to save shape keys in any mode other than Shape Modeling or Secondary Shape.

If you just did some modeling that you wanted to store in a shape, which is the mostly likely situation, there are two ways in which you can fix this:

• Click Cancel. In the explorer, select the deform operators which were meant to model the shape, then drag-and-drop them into the object's Shape Modeling region in its construction history

• Click Cancel. Delete or undo the deformations which were meant to model the shape, switch to a Shape Modeling mode, and reapply the deformations. (Switch to Secondary Shape mode for setting shape keys in relation to an envelope’s animation).

Remember that you need switch to Shape Modeling mode before deforming the geometry for setting shape keys. Any changes to the geometry you make before switching will be changes to the reference geometry (Modeling region), and will not be saved as shapes for the shape key.

Creating Shapes in Shape Modeling Mode

If you want to deform the geometry of an object to create shape keys for it, you need to first switch to Shape Modeling mode. When you save or store a shape key in Shape Modeling mode, the deformation operators you apply for shape animation are stored in the Shape Modeling region.

The Shape Modeling region is above the Modeling region in the object’s construction history and contains the Cluster Shape Combiner node. The Cluster Shape Combiner is an operator that is created as soon as a shape is created, such as if you save a shape key or bring it into the mixer. The Cluster Shape Combiner must always be at the bottom of all the operators used in the Shape Modeling region because it uses all deformation operators above it to create the shape keys.

When you create a shape clip by saving or applying a key, all operators in the Shape Modeling and Secondary Shape regions are removed except for the Cluster Shape Combiner . This protects animated deformations that may be present in the regions above, such as envelopes in the Animation region, from being removed.

When you open or import a scene or model created in versions of SOFTIMAGE|XSI previous to v4.0 and an object has shape animation, the position of the Cluster Shape Combiner node determines the end of the Shape Modeling region.

To use the Shape Modeling construction mode

1. Select Shape Modeling from the Construction Mode list on the main menu at the top of the interface.

2. Create shape keys as usual for an object or cluster using any deformation operator or by moving points.

New deformations are applied at the top of the Shape Modeling region, above the Cluster Shape Combiner.

3. At any time, you can display the final result (the result of all operators in all regions) or the just the current mode (the result of all operators in the current region and those below it) as described in Construction Modes and Regions in the Modeling and Deformation Basics guide.

You can change operators’ regions after they have been applied by moving operators in the stack, but the usual caveats still hold—see Changing the Order of Operators in the Modeling and Deformation Basics guide).

Creating Shapes in Secondary Shape Mode

If you want to use the animated envelope for creating shape keys, you can switch to the Secondary Shape construction mode and save shape keys in reference to the animated envelope’s geometry. This is a useful mode for tweaking the envelope’s deformation for shape animation, such as for fixing the corner or a mouth or an elbow crease, or doing pose-based deformations using the Link with commands (see Deforming a Shape Based on Poses or Orientation).

Saving shape keys in this also mode prevents the Envelope operator in the Animation region from being deleted when you bring the shape keys into the mixer to create shape clips.

The Secondary Shape mode currently works only with envelopes. Creating shape keys in this mode may not give satisfactory results if you use it with other animated deformations.

The Secondary Shape region is at the top of the construction history. When you save or store a shape key in Secondary Shape mode, the operators in the Secondary Shape and Shape Modeling regions are stored in the shape.

Then the operators in both these regions are removed when you create a shape clip, such as by saving or applying a shape key. All shape keys are applied at the level of the Cluster Shape Combiner at the bottom of the Shape Modeling region, including shapes created in Secondary Shape mode.

To use the Secondary Shape construction mode

Here’s a typical scenario in which you would want to use the Secondary Shape mode:

1. The shape-animated object has been applied as an envelope to a skeleton and has an Envelope operator in the Animation region. The envelope is animated by the skeleton, such as by the jaw bone for animating the mouth movements for lip synching.

2. Select Secondary Shape from the Construction Mode list on the main menu at the top of the interface.

3. Use any deformation operator or move points on the envelope, such as to fix up the mouth region in relation to how the envelope is animated. New deformations are applied in the Secondary Shape region.

4. Save, store, or replace a shape key as usual.

Muting the Envelope Automatically

If you don’t switch to the Secondary Shape mode when working with envelopes, you can also set up XSI so that the Envelope operator (and any other deformation operator) is muted automatically when you create shape clips in the mixer.

To do this, choose Deform > Shape > Preferences, then select the Mute Deforms on Instantiation option in the Shape Preferences property editor before working with envelopes or other deformations.

However, if a deformation operator doesn’t support muting, it is deleted even if this option is on.

You can set this command to be active by default with the Shape Animation preferences—see Setting Preferences for the Shape Animation.

SOFTIMAGE|XSI v.6.01

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