"Tim Nikias" <JUSTTHELOWERCASE:timISNOTnikias(at)gmx.netWARE> wrote in
message news:41b60788@news.povray.org...
> So, what I have: two meshes of the same tree. One is with all the tiny
> branches, the other with just the big ones. What I want to do is place
> spheres for a blob onto the less intricate tree, and then use it in
> conjunction with the detailed tree. Thus, I get snow on the bigger
branches
> for the detailed tree.
>
> Now, does anyone have any ingenious SDL-Code which would place the spheres
> on the tree via trace()? I could go about, generate a field with millions
of
> particles and then just drop them, those that stick will stay, the rest
will
> get deleted, but I'd rather use a more sophisticated approach, which
should
> be faster. My initial idea was to generate a top-down image of the tree,
> white=tree and black=empty space, and before actually shooting trace(), I
> check this image if there's any tree beneath it. With an even distribution
I
> could thus quickly generate all the spots on the tree, but I'd have to
> generate thousands of starting points of which again thousands will get
> discarded once I test them against the image.
>
> Anyone have any ideas or suggestions? I don't mind scripting the thing
> myself, I just need a good algorithm which will work faster than
> brute-force.
>
> Regards,
> Tim
>

http://graphics.stanford.edu/courses/cs448-01-spring/papers/fearing.pdf
or his website
http://www.cs.ubc.ca/nest/imager/contributions/fearing/snow/snow.html

i've been wishing i knew where to start for about 2 months now. as the
author notes, top down doesn't work real well. You want to go from the
ground up, since snow has a habit of drifting and avoiding obstacles as it
falls. so even if ground doesn't have any direct exposure to the sky, it
still might have a thin layer of snow. I'd really like to implement this for
POV, it is one thing i'd really like to do...

i mean, it wouldn't be very hard to pick N number of points on the snow
target (the object which snow will cover) and use some algorithm for
determining the snow density at that point. I don't know how to create a
mesh of those points though. I also don't know how to do the "flake dusting"
he talks about. But oh well, one can dream.


-ross

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