Game Development Reference
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Figure 15.1 Subdivision using a linear model, the butterfly model and the
Catmull-Clark scheme.
can be very important. Figure 15.2 shows the effect of subdivision on a
very low resolution mesh. The sample on the left uses butterfly
subdivision, which is interpolating, while the sample on the right uses
exactly the same control mesh, but this time the subdivision scheme is
approximating. Interpolating subdivision has the effect of slightly swelling
the original mesh if the original mesh is principally convex. Approximating
subdivision shrinks the mesh; the fewer polygons in the original mesh, the
more exaggerated this result. With a very low polygon control mesh, the
subdivided mesh can differ greatly in volume and shape from the base.
Approximating subdivision is the scheme used by Pixar for most of their
Figure 15.2 Using interpolating and approximating subdivision on a low polygon
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