Order of Operators

When you're close to finalizing the envelope and shape animation or deformation on your characters, there are still a number of decisions that you'll need to make in order to optimize your characters performance. The order of operators on a particular piece of geometry make a big difference when the time comes to begin animating. To the right is an image of the order of operators on a given character. This order of operators lends to errors later on in the production process.

When I built the character, I enveloped and weighted first, freezing my envelope weights when done. Afterwards, I began the process of building shapes into the face and added deformers whose shape and amplitude were controlled with weight maps and custom parameters. Following this workflow, the push and taper operators will be above the Envelope Operator, as should the Cluster shape combiner, because they were all built in after enveloping.

If I had left these operators in the above order, XSI calculates the effects starting from the top Operator in the stack and then finishing with the last operator. Everything looks OK in the default position if you manipulate the characters deformers or slide shape values in the mixer. As soon as you begin to move the character into pose and then start animating, all of the shapes or deforms you initially set will begin to register incorrectly. They begin to change because XSI first calculates the shapes, and then adds the effect of the envelope on top. Smiles turn to grimaces, and frowns turn to twisted geometry.

 

To rectify these types of issues, make certain that your Envelope Operator resides at the top of the Stack. You can do so by dragging and dropping it on top of the very top Operator. Your stack should appear something like the image to the right. In this order, your shapes and deformers should become rather predictable.