Kirk Andrews wrote:
> I'm posting in the hopes that perhaps some of the brilliant minds around here
> could improve upon what I'm doing.  In fact, I'd be surprised if no one around
> here has tried this before, but I couldn't find anything like it yet.

I worked on something similar months ago:
http://news.povray.org/povray.binaries.images/thread/%3C489e1fe2@news.povray.org%3E/?ttop=290287&toff=100

But my technique involved simply moving the next point according to the 
normal of the hf at any given tested point. This was a sloppy way of 
handling it, because oftentimes there would be a "ping-pong" effect 
along the rivulets. I had originally considered testing the lowest point 
like you do, but ended up going forward with the easier way, which 
turned out being difficult to work with :( Attached is an image I 
rendered today using my trace/normal technique. I managed to improve the 
shading somewhat, allowing the rivulets to "cut" into the height field 
pattern in one render step. If I work on this again, I think I will try 
to test for lower points (like you are doing) instead of using trace(). 
It can be done by testing patterns, which might reduce the parse times. 
In fact, erosion could take place during an animation sequence, with 
erosion working on earlier erosion over time, without using height 
fields at all... Hm.

Sam

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