Try to keep exactly four surfaces at each intersection between surfaces, which allows for simple stitching of surfaces to be applied, keeping all surfaces tangent all the time throughout the animation. When it is impossible to maintain four surfaces at each surface intersection, use five-cornered intersections. The surfacing pattern shown in this eye diagram can be used at eye, arm, hip, mouth and any other locations.
The intersection shown in Figure 4 has five surfaces coming together at one point. Using this technique allows multiple surfaces to be introduced into a regular grid of surfaces without introducing triangular patches. When you align surfaces later, you will need to use special techniques to maintain tangency across this special condition.
Do not introduce patch boundaries in areas of detail. When you are trying to maintain tangency across surfaces in areas of detail, you do not have as much control as you need to keep detail and maintain tangency. Try to create detail from the surface and introduce patch boundaries across areas of the least detail Detail can be added by adjusting CVs or by increasing isoparms, if necessary.
The lines that were digitized are set up so the lines can easily be used to create surfaces. Note how the lines radiate from the eyes and mouth so they can create radial surfaces around those parts of the face. Whenever possible, try to determine ahead of time how the surfaces will be built, then digitize accordingly. The lines shown on Figure 7 indicate the construction of the final surfaces.
Convert the lines into B-splines. If you digitized NURBS curves from inside Maya or imported B-spline digitized data, this next step is not necessary. Select the degree-1 NURBS curves in the file. When all of the lines are highlighted, use Object, Edit, Fit B-Spline to create degree-3 NURBS splines where the original digitized lines were.
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