Wire Deformer Rig for Face Shape
Creation
For the purposes of creating a fast way to create blend shapes, I
created a wire deformer rig. The wire deformer makes the creation of
expressions very quick. By manipulating the points on the curves, I was
able to move the surface of the skin in a very elastic, natural way.
Another thing that was working in my favor, in a big way, was that
the model being manipulated was a low-resolution cage. This version of
the model was very fast to edit, and the smoothed results always looked
better than if the model had been edited in high-resolution.
During the process of modeling blend shapes, the animation rig
that had the jaw rotation skeleton was used to ensure that the rotation
used for the blend shape jaw matched the rotation used by the jaw on
the actual animation rig.
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| [Figure
48] indicates where the curvers were drawn to create the wire
deformers used to edit the model for blend shapes. |
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Cleanup and Testing
The modeler needs to test and clean up blend shapes after making them.
Testing blend shapes is a critical part of the modeling process. Many
things can go wrong during the creation of blend shapes. Any time the
model is exported from Maya in another format (like .obj) will scramble
the order of the polygons in the model. Anything that affects polygon
ordering will create many problems.
When testing the model, the modeler should be looking for technical
problems as well as aesthetic problems. The technical problems will
become evident quickly and require no additional discussion.
The aesthetic problems include the following:
- Does the shape look natural? Does it look like a shape that would
normally occur on the face?
- Does the shape cause undesirable stretching and twisting? Most
expressions on a real face do not cause too much stretching of the
skin, but on a cartoon character, this is not the case. In extreme
poses, there will be some stretching that needs to be dealt with, so
the modeler needs to determine whether the stretching is acceptable or
not.
- Are the polygons distributed as evenly as possible for the
blend shape? Uneven distribution of the polygonal topology will cause
the geometry and textures to deform unnaturally. The skin in a
character is an elastic sheet that covers the bones and muscles, so the
modeler has to determine if that sheet is getting stretched too much in
one place.
- Test the final blend shapes with the hair, eyes and teeth in
place. Are there any intersections of the skin surface with the hair,
eyes and teeth?
UVs
In order to get the character rendered, the modeler needs to apply UV
coordinates to the character. The process of editing UVs has a fairly
straightforward goal: Will the texture artist be able to paint textures
on this character that will not twist or deform unnaturally?
There are many methods for applying UVs. For this section, the
basic application types will not be discussed. In order to texture this
model, there were two primary methods employed in the application of UV
coordinates. One method was used solely on the head, and the other
method was used on the rest of the character.
