Thursday, June 5, 2008

Rotating bunny

Isometric perspective and a little animation can be used to conveniently visualize intricate 3D models:
The 1,889 points defining the surface of the bunny statuette have been obtained from the Stanford 3D Scanning Repository at the Stanford University Computer Graphics Laboratory. We have used the same Filmation technique exercised in a previous entry, with one important simplification: if we ignore the (rare) antitransitive cycles of the "is behind" relationship and consider a situation where all the elements in the scene have the same dimensions (as in our current setting), we can approximate the "is behind" relationship by any lexicographical order in the (x,y,z) coordinates, or, if we let the approximation be even coarser, by any order in only one of the coordinates. Since our statuette rotates along the z axis, the elements' z coordinates remain constant, so we can sort the elements by their z coordinate at the beginning of the program and use this ordering to assign a fixed drawing priority, thus sparing us the recalculation of the drawing ordering at each animation step. The resulting rendering anomalies (elements appearing in front of others when they shouldn't) are hardly noticeable.

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