From Play-Doh to Softimage: Using Shape Animation, Clusters & Qu
About Shape Animation

Shape Animation as described by Softimage "allows you to animate the entire geometry of an object." It is the process of interpolating the shape of an object on a point by point basis. Shape animation requires that the objects being deformed have the same number of points. The shape animation process can be as simple as linearly keying two or more shapes derived from the same three dimensional object (see Candle and Dancing Coat Hanger Tutorials) or a bit more challenging by blending overlapping key shapes to create more expressive characters (see Cat Face Tutorial, later in this file).

To create just the look you might desire from your shape animation, the concept of interpolation is important to understand. Interpolation is the technique that calculates all the in-between positions from one key point to the next. In Softimage shape animation can be interpolated in one of two categories, average or additive.
The average interpolation category is an average value between key points. For example, you have two shapes, one shape starts at frame one and interpolates into shape two by frame 10. At frame 5, the shape is made up of 50% of shape one and 50% of shape two, at frame 8, the shape is made up of 20% of shape one and 80% of shape two, and so on... Average interpolation is the default in Softimage.
The additive interpolation category means that two or more shapes can be combined at the same point in time. Say, for example, you have three different facial shapes: One is a smile, one is growing horns, and the other has puffy checks. With additive interpolation you can combine all those shapes to create a smiling, puffy-checked devil or any combination thereof. You can also vary the scaling on any of those shapes to create exaggerated or subtle effects with your facial expressions.
In Softimage, once a shape animation function curve is created you can adjust from average to additive interpolation and vice versa. This adjustment can be found in the Shape_Shape List dialog box. Another adjustment to note in either of the additive or average categories is the type of the interpolation. In Softimage, there are three types of interpolations that can be used with average or additive. They are as follows:
Linear: a linear interpolation means that from key point to key point the shape will deform in a linear direction with no acceleration or deceleration into and out of a key point along the spline.
Cardinal: a cardinal interpolation means that from key point to key point the shape moves along a curved spline, creating movement with subtle changes in acceleration.
Weighted: a weighted interpolation creates a function curve for each key shape or cluster. Having one function curve per shape allows an animator to emphasize one curve over the other or in other words "weight" them.
The types of interpolation for shape animation can by found in the Shape_Shape Interp. menu option. It is important to note that the effects of an additive interpolation can only be simulated when in the weighted interpolation type. To see and adjust the function curve for weighted interpolation you must go to Fcrv_Select Shape Weight (see Cat Face Tutorial).

About Cluster Animation

Shape animation is the technique of deforming the whole geometry of a mesh. Cluster animation is designed to help animate assigned areas of a geometry .You can assign as many clusters to a mesh as needed. It is as simple as tagging an area on your model, lets say the nostril of your dragon, and assigning it a cluster name by going to Shape_Set Cluster or Tag_Set Cluster.

Softimage also has the added option of creating a center for your cluster. In the Shape _Set Cluster dialog box you can check "create center" and a null will be placed in the center of your chosen cluster area. In your schematic view you will notice how the null has become a child of the object with the cluster. This null can then be selected and your cluster can be proportionally scaled, rotated and translated.
Setting keyframes for clusters are different depending on if you are moving your clusters as a tagged area or by a null-center. To set keyframes as a tagged area select Shape_Save Cluster Key. To set keyframes on a null center go to Save_Key Object.

Tutorial Examples

Featured below are a series of tutorials related to shape and cluster animation. These tutorials are written assuming the user is somewhat familiar with Softimage and its basic modeling tools. It is recommended to read over the tutorial, and to use the basic concepts presented as a means to a users own creative projects.

Tutorial: Dancing Coat Hanger

Average Shape Animation Using Modeling Relation
1. Turn on Preferences_Modeling Relation.
2. Draw_Curve NURBS (you can use any kind of spline).
3. Draw a coat hanger shape.
4. Get-Primitive_Circle (leave the circle at its default steps and in the global center).
You will extrude the circle along the coat hanger spline, so scale if necessary. You can also readjust the shape after the extrusion since modeling relation is on.

Please Note: the more points on your spline or circle, the more steps your 3D object will have (more steps means a smoother surface, but a more complex mesh) . A NURBS spline will create an infinitely smooth object. Go to the Info-Selection if you would like to make the step value of that NURBS lower than 10).

5. Select your coat hanger spline. Choose Surface_Extrusion. In the dialog box select NURBS (if you would like to maintain the objects smoothness) and the Extrusion along Curve option. Exit dialog box.
6. Pick on the Circle . Adjust if necessary, by moving points on the original spline. You now have your first shape (see Original Coat Hanger Shape graphic).
7. Select the original spline. Duplicate three times. Move the points on each duplicate spline to reflect a different shape.
8. Perhaps make one in the shape of the number eight, another a question mark, another a lamp post. Line the shapes up in the order you want to keyframe them.
9. Set up the animation in the Motion Module.
10. Select the original spline. Move to frame 1.
11. Choose SaveKey_Shape. Move to frame 20.
12. Choose Shape_Select Key Shape and pick spline shape number two.
13. Continue process with the next two shapes.
14. Play back the animation.

To alter the animation you can go to your Function Curve and manipulate key points. Each key point in your function curve represents a different shape. You can easily change how the shapes move one into the other by adjusting the interpolation of the function curve (Fcrv_Edit, Interpolation). To change the order of the shapes, set your timeline to where you want to add, remove, or replace key shapes, go to Shape_Shape Library and select the new shape you want.

Set a Shape_Select Key Shape keyframe.