Metamorphosing Same Topology Items

Set key shape lets you transform one object into another object by transforming the CVs. There are two types of interpolations that can be created:

Keyshape

Key shape interpolations are created by animating the CVs of the base object so that they will match the positions of the target object.

ShapeShifter

ShapeShifter interpolations are created by placing the CVs of the base object into clusters, and then providing a method for the amount of transformation to be selected interactively. ShapeShifter interpolations also allow various target shapes to be mixed together.

How to Use

1

Select Anim > Set key shape or click on its icon.

The system prompts:

Pick the curves or surfaces which are to change shape. Press GO when ready.

2

Click on the curve or surface. The system prompts:

Enter a keyframe value(s) for the picked item(s) current shape (last frame set is 0):

3

Type a number and press Enter. The system displays the message:

Setting keyframes for 4 CVs of object (curve#2)

You are then prompted to pick the curve or surface to match and set keyframes for these elements.

How to Use Key Shape Interpolations

1

Begin with an original piece of geometry and copy it as many times as you like.

2

Manipulate the shape of each copy by applying Xform transformations to the CVs or DAG nodes of each copy, or by adjusting the CV weights using Curve Edit > Modify > Adjust weight.

3

When you select Set key shape, you are prompted to select the curves and surfaces that are to change shape, then enter keyframe times at which the objects should maintain their original shape.

You are then prompted to select another shape and enter a keyframe time at which the original objects should take on this new shape. The process of selecting new shapes can continue until all modified copies have been selected and keyframe times are set for them.

If you want to keep the original geometry shapes, make a copy of the original objects before invoking the function, or make sure you set a keyframe time for the original shape of the objects. This way, you can return the objects to their original shapes by viewing that keyframe time.

4

When you select another shape for the original geometry to assume, the original geometry immediately takes that shape during the selection process and loses its original shape.

The key shape animation is created by animating each of the CVs of the original objects. The interpolation between the CVs (the process that transforms one key shape into another) is, by default, a smooth interpolation. You can adjust this interpolation by modifying the tangents of the animation curves of the CVs in the Action Window .

For more information on using the Action Window, see Animation > The Action Window on page 138.

When you complete the key shape animation, you can delete the animation and start again if you are not satisfied with the results. However, before deleting the animation, you may want to restore the original shape of the transforming object. If you typed a keyframe time for the original shape, this is easily done by selecting Anim > View frame and typing the time of that keyframe.

When satisfied with the animation, you can delete the intermediate objects as their shapes are now recorded as keyframes.

How Set Key Shape Works

You can use any number of interpolation shapes. Each shape must have identical topology. It is recommended that you copy the original geometry (the geometry shape for the first keyframe), then manipulate the copied geometry into the desired shape for subsequent keyframes. If you are interpolating curve shapes, you can use Curves > New curve and set Knot Spacing to Uniform in the option window to ensure that you create curves with identical topology.

The objects that are used to transform the original object must have the same topology as the original object. Surfaces with same topologies have the same number of CVs in the U and V parametric directions. Curves must have the same number of CVs. The corresponding CVs of each object should have the same multiplicity. CV multiplicity can be changed using Curve Edit > Modify > Multiplicity.

Example

In this example, a sphere is used to create an interpolation animation where the sphere takes on a diamond shape through 10 keyframes, then reverts to its original shape through another 10 keyframes, and back to the diamond in another 10 keyframes.

Place two spheres

1

Select Objects > Primitives > Sphere and place a sphere in the Front window at -5,0,0.

2

Place another sphere at 3,0.0. Both of these pieces of geometry are identical in topology.

Scale and move the spheres

1

With the second sphere active, select Xform > Scale and type 4 to scale the sphere to a value of 4 units.

2

Select Object Display > Control - and make sure the CVs is toggled ON (indicated by a check mark). Press GO.

3

Select Pick > Nothing to ensure that no geometry is active, then select Pick > Point types > CV and using the bounding box technique, select only the first row of CVs along the top of the second sphere.

4

When the CVs are active, select Xform > Move and use the right mouse button to move these CVs upwards along the Z-axis to elongate the top of the sphere into a pointed shape.

5

Select Pick > Nothing to ensure that no geometry is active. Select the last row of CVs along the bottom of the second sphere.

6

When the CVs are active, select Xform > Move and use the right mouse button to move these CVs down the Z-axis to elongate the bottom of the sphere into a pointed shape.

7

Select Pick > Nothing to ensure that no geometry is active. Select the middle row of CVs of the second sphere.

8

When the CVs are active, select Xform > Scale and use the left mouse button to scale these CVs up to create a bulge in the middle section of the shape so that it resembles the diamond shape shown in the diagram at the left.

The original sphere defines the start shape and the modified sphere defines the final interpolated shape. Although only two shapes are being used in this example, several interpolated shapes could be used.

Set a keyshape

1

Select Pick > Nothing to ensure that no geometry is active, then select Anim > Set key shape. The system prompts:

Pick the curves or surfaces which are to change shape. Press GO when ready.

2

Click on the first sphere. Once selected, it is highlighted to indicate the object whose shape will be changing.

If you were including other geometry animation, you would continue to select geometry in response to the prompt.

A small GO icon appears in the lower right corner of the active window, and the system continues to prompt:

Pick the curves or surfaces which are to change shape. Press GO when ready.

3

Click the GO icon to continue, and the system prompts:

Enter a key frame value(s) for the picked item(s) current shape (last frame set is 0):

4

Type 1 followed by a space, then type 20 and press Enter.

This indicates that the shape of the initial sphere is to be used for keyframes 1 and 20. The system prompts:

Pick the curve or surface to match.

5

Click on the second sphere. The original geometry changes shape to match the selected geometry.

If the surface you select to match does not match the topology of the surface you select to change shape, an error message is displayed and the system prompts:

Pick the curve or surface to match.

If the topology of the selected surfaces match, the system prompts:

Enter a key frame value(s) for this shape (last frame set is 20):

6

Type 10 followed by a space, then type 30 and press Enter.

This indicates that the shape of the manipulated sphere is to be used for keyframes 10 and 30.

7

Select Animation > Playback to view the interpolation animation.

During playback, the initial sphere shape interpolates into the shape of the manipulated sphere through frames 1 to 10. It then interpolates back to the original shape through frames 10 to 20, then back to the manipulated shape through frames 20 to 30.

How to Create ShapeShifter Interpolations

With ShapeShifter, an unlimited number of expressions and forms can be combined to transform objects into a variety of shapes, as well as mixing facial expressions together.

ShapeShifter transforms (or "morphs") one shape into another by transforming CVs using clusters and expressions. This lets you select how much of the interpolation should be applied at any particular time, as well as mix several different target shapes together. Because clusters are used, the underlying geometry can be polygonal or NURBS. Source and target objects can also be hierarchical, as long as the hierarchies match.

ShapeShifter greatly simplifies complex facial animation. For example, given a base (or neutral) face, and other faces that represent a smile and frown, you can create a face which is 75% smiling and 50% frowning and control the timing of the interpolation between the various targets.

Since the interpolation is done by determining the translation which will make a CV in the source object move to the corresponding CV in the destination object, the two objects must share the same topology (that is, they must have the same number of CVs in both u and v).

The interaction is simple - for each target, a "control" object is created. The X translation of this object determines the amount of transition from the base to the target object and, of course, can be animated. For example, to have the neutral face "ease-in" to a smiling face over two seconds, you simply move the control object to the left of the slider, set a keyframe at 0, then move the control object to the far right and set another keyframe at 60. Set the appropriate animation interpolation in the Action Window on the control object's X_translation channel (or use an expression) and you're ready to go.

Example

The following example shows how ShapeShifter is used to combine features from two separate head expressions.

The middle head combines the features from the other two heads. The head on the left has been manipulated to exaggerate the chin and horns of the little devil. The head on the right has a pointier head, as well as some devilishly handsome ears.

Moving the control object of the top slider causes the middle head to acquire some of the features of the head on the right. Notice how the middle head is also pointier, and has begun to sprout its own pair of ears. The amount of the shape shifting can be controlled by the position of the slider.

As you start to move the control object of the bottom slider, notice how the middle head begins to acquire some of the characteristics of the left head as well as retaining the effects of the right head.

Notes:

If Create control geometry is checked, a trianglular object is included in the control object DAG node.

If Create slider geometry is checked, a DAG node containing the geometry representing a slider bar and a locator object for its name are also created.

This last object is created in a templated state.

To set the options:

1

Select Anim > Set key shape -, then click ShapeShifter in the Interpolation section of the option box.

2

At the prompt for the source object, select the head at the left.

3

At the prompt for the target object, select the middle head.

4

At the prompt for the control object name, type chin.

A DAG node containing 3 clusters and a DAG node for the control object are created.

Hierarchical ShapeShifter Interpolations

ShapeShifter interpolations can also be created between objects consisting of many grouped geometry nodes.

• To create a ShapeShifter interpolation using hierarchical objects, pick the objects at the base nodes that form them. The geometry topology must match between the two objects.

• To match up the two objects, traverse individual geometry nodes from left to right in the SBD window. Any non-geometry nodes are ignored during the matching process.

For grouped objects, the Shape Center is created as follows:

• First CV- the first CV of the first (left-most) geometry node in each object is used as the shape center.

• Centroid- the volumetric center of all grouped objects is calculated.

• Scale Pivot- the scale pivot of the picked DAG node for the base and target objects is used.

The following is an example of the SBD view with two diverse hierarchies, which can still be used for ShapeShifter interpolations. Geometry nodes are matched up going from left to right through each object.

Set Keyshape Options

Select Set key shape- from the Anim menu or double-click on its icon to display the Set Keyshape Options window.

Interpolation

The Interpolation options determine the type of shape interpolation that is performed.

Key shape

Creates CV animation that interpolates from the original object to the new shape.

ShapeShifter

Creates a group of clusters and control objects that interpolates from the original object to the new shape.

Shape Center

The Shape Center options determine the placement of the new shape with respect to the current shape of the object.

First CV

The first CV on a NURBS curve or surface is represented as a small square.

The First CV on the new shape matches position with the first CV on the original object. The easiest way to determine which CV is the first one on a object is to pick the object, then use the pick walker (Shift - arrow down) to walk to the first CV on the object.

Centroid

The volumetric center of the new shape matches position with the volumetric center of the current shape.

Scale Pivot

The scale pivot of the new shape matches position with the scale pivot of the original object.

ShapeShifter Options

When ShapeShifter Interpolation is selected, several additional options are displayed in the Set Keyshape Options window.

Control name

The Control name options determine how the name of the control object is displayed. The control object is the object which when transformed using Xform > Move will cause the original object to change shape.

Prompt

A prompt is displayed asking for the name of the control object.

From target

The name of the control object is derived from the name of the target object.

Control parameter

The Control parameter options determine which translation direction of the control object will affect the ShapeShifter interpolation.

Moving the control object in either of the other two axes has no effect on the ShapeShifter interpolation.

X,Y,Z Translate

Moving the control object in the X, Y, or Z direction determines the amount of interpolation applied to the original object.

Control range

The Control range settings determine the range of translation of the control object that affects the ShapeShifter interpolation. These settings also control the placement of translation of the control object on the axis.

• When the control object is positioned at the start point, the ShapeShifter interpolation has a 0% effect (the original object is not interpolated towards the target shape).

• When the control object is positioned at the end point, the ShapeShifter interpolation has a 100% effect (the original object assumes the same shape as the target object).

Limit translate to range

When checked ON, the control object cannot be moved outside of this Control Range and has no effect on the ShapeShifter interpolation. The default setting is OFF, which allows "undershooting" and "overshooting" of the interpolation.

Add 0% cluster CVs

When checked ON, all CVs are added in the original object as a cluster, whether or not the CV will ever be affected by the ShapeShifter interpolation.

When checked OFF, only the CVs that need to be transformed are added to the clusters, reducing the number of CVs being affected by the cluster. The default setting is OFF.

Create control geometry

When checked ON, geometry is created (a small triangle) and is attached to the control object so that it can be more easily manipulated. The default setting is ON.

When checked OFF, the control object becomes a NULL DAG node, which can be picked from the SBD window.

Create slider geometry

When checked ON, geometry is created (a slider bar with the control's name) and is attached to the control object so that the control range can be more easily identified. The default setting is ON.

Slider position

The location, in world space, of the slider geometry can be set here. This lets you position the object anywhere that is convenient.