Hi Lars,
To define trees in Radiance, you can either use an impostor as you do in your CAD system, and apply a "colorpict" to it, or (as I prefer), model the tree as detailed geometry and compile into an octree for the "instance" primitive. This is very efficient, since a single tree model may be duplicated throughout your scene without adding to associated scene memory. You cannot easily get holes in a tree otherwise, as you would have to use the "mixdata" type with "void" as one of the modifiers, and translate your texture into a large, ASCII data file. It's doable, but the results won't look as nice as a real tree, and won't be much faster to render, either. Ray tracing is very fast at rendering complicated geometry -- much faster than a typical CAD program.
There is a pine tree in the standard Radiance distribution, but I never got around to modeling anything more elaborate....
-Greg
Greg Ward wrote:
Hi Lars,
To define trees in Radiance, you can either use an impostor as you do in
your CAD system, and apply a "colorpict" to it, or (as I prefer), model
the tree as detailed geometry and compile into an octree for the
"instance" primitive. This is very efficient, since a single tree model
may be duplicated throughout your scene without adding to associated
scene memory. You cannot easily get holes in a tree otherwise, as you
would have to use the "mixdata" type with "void" as one of the
modifiers, and translate your texture into a large, ASCII data file.
There is a "mixpict" modifier available at least in 3R1p20 and in
the Windows binaries included with Rayfront (but not in those
from Desktop Radiance). This would eliminate the need to
translate anything into ASCII data, you just need to create a
mask picture. Of course, all the other things said so far remain
true anyway.
The best advice is probably to exclude the tree geometry from the
ambient calculation as mentioned in another reply. Unfortunately
this is not yet directly supported by the Rayfront interface
(which Lars is using), but you can still add the necessary
parameters to the rif file manually. Rayfront will preserve those
entries when reading the file, and correctly pass them to rpict
and friends, even if it doesn't expose them in the GUI.
-schorsch
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--
Georg Mischler -- simulations developer -- schorsch at schorsch.com
+schorsch.com+ -- lighting design tools -- http://www.schorsch.com/
Hi!
The best advice is probably to exclude the tree geometry from the
ambient calculation as mentioned in another reply. Unfortunately
this is not yet directly supported by the Rayfront interface
(which Lars is using), but you can still add the necessary
parameters to the rif file manually. Rayfront will preserve those
entries when reading the file, and correctly pass them to rpict
and friends, even if it doesn't expose them in the GUI.
In fact, I am currently working on the scene without rayfront. Is there a way
to make rayfront generate one octree per imported geometry (I used
rad-geometries, but the dxf-import would be ok, too)? If I try to oconv all
my rad-files in one run, I get the famous oconv overflow 
So I created one
oct per "object" (in fact per color) and have a instance file "model.rad"
where I put all my octs together.
CU, Lars.
Hi!
To define trees in Radiance, you can either use an impostor as you do in
your CAD system, and apply a "colorpict" to it, or (as I prefer), model
the tree as detailed geometry and compile into an octree for the
"instance" primitive.
I used geometry now, with replmarks and instances on 3r4b. Works fine, thank
you for your reply. In fact, I get the quite large model rendered on my old
laptop with 128 MB...
CU, Lars.