The following pictures of a 2964-point shirt used 50 horizontal slices in each of 15 different orientations for the visibility cones. It took 58 seconds on a 500 MHz Pentium to compute all the visibility cones (on both sides of the surface).
The shirt is illuminated with a uniform hemispheric diffuse source, like the illumination of a cloudy day. Given the visibility cones from the preprocessing step above, it took 1.5 seconds to compute the cloth shading.
Note the subtle shading inside the shirt, and the darker creases under the arms and where the cloth folds inward.
The following image is flat shaded to show the size of the mesh elements.
My sincere thanks to Xavier Provot and Jeremy Denise of INRIA for the great model!