Inspired 3D: Character Modeling Tutorial (continued from page 1)

[Figures 3-6] Improper surfacing strategy diagram (far left). Surfacing strategy diagram for transitioning round objects into larger, smooth areas (center left). The five-cornered intersection (center right). Do not add patch boundaries in small tight areas (far right).

Never create a triangle. In nature, there are many places where the natural flow lines of the contours of the face seem to come to a point. Figure 3 shows improper surfacing strategies. The triangular region in the corner of the eye will never surface correctly. The detailed areas at the corner of the eye are bad places to try to maintain tangency between surfaces.

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.

[Figures 7 & 8] The foam sculpture (left) was digitized using lines used in the construction of the actual surfaces. Convert degree-1 curves into degree-3 curves using Fit B-Spline (right).

The data can be imported as .obj or .dxf if you have polyline data to start with. Maya does not actually support polylines. When the data is imported into Maya, the polylines are converted into degree-1 NURBS curves.

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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