
598 Chapter 12 Surfaces
Figure 12.9 Subdivision that has no cracking.
Figure 12.10 Subdivision that contains more complicated cracking.
the midpoints to the corners at those edges. Recurse on the four subblocks. The
nonuniform subdivision requires two passes: one to generate the vertices of the final
mesh and one to fix the cracking. While the second pass may not be that expensive, it
must handle the type of subdivision shown in Figure 12.10.
Now let us consider a single-pass algorithm that prevents the quadtree subdivi-
sion of a more detailed block. The main idea is to do a depth-first traversal of the
quadtree, but to use topological information about ...