Hi,

I've been experimenting with different ways of rendering non-intersecting
grains. One way to approximate this is to make each grain a blob, and then to
subtract negative blob components from it using neighboring points. The method
is similar to how I made the underwater air bubbles, except I now have access to
a list of each point's nearest neighbors, which means the parse time is
*significantly* reduced.

This scene took 11 seconds to parse. It took only 7 minutes 9 seconds to trace
with one 7x7 area illuminating area light. Blobs, when used in this manner, are
very efficient. Total particle count: 10,090.

The Voronoi calculations (using an external program) took about 1 minute to
solve for 32,768 points. However, the output from that program only needs to be
created once. The resulting data can then be used in different ways. For this
image the actual points filled a cubic volume, but (in POV) I kept only the
points which existed in a sphere and below a plane. That is why only 10,090 out
of 32,768 points made it into the final render.

The next challenge will be to vary the particle sizes without having them
produce incorrect results :/

~Sam

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