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- From: paik@mlo.dec.com (Samuel S. Paik)
- Subject: Re: PoV question: Is there a way to render shadows but not objects?
- Message-ID: <1993Jan22.012339.13856@peavax.mlo.dec.com>
- Sender: usenet@peavax.mlo.dec.com (USENET News System)
- Organization: Digital Workstations Software Group
- References: <1j761gINN8ps@topper.ksu.ksu.edu> <1993Jan18.152328.492@qdeck.com>
- Date: Fri, 22 Jan 1993 01:23:39 GMT
- Lines: 23
-
- In article <1j761gINN8ps@topper.ksu.ksu.edu> jregehr@topper.ksu.ksu.edu (John David Regehr) writes:
- >
- >I am working on raytracing groups of plants, and I would like to make
- >images of just the shadows cast by the plants - sort of the opposite of
- >using the noshadows keyword.
- >If anyone knows how to do this, I'd like to hear from you. Thanks.
-
- Here are two ideas:
-
- If you have source code to the ray tracer, you could modify the
- lighting code so that shadow rays stop at all surfaces, or, more
- flexibly, stop shadow rays at all surfaces that have some (new)
- attribute set. The last could be hacked quickly if you select some
- existing attribute you aren't using and use that. However you might
- want to cast ``transparent'' shadows...
-
- In Renderman, here is a simple idea:
-
- Use shadow depth maps for the lights. Do the shadow depth maps with
- all the scene objects, then render the scene, using those shadow depth
- maps, but without the objects you don't want to see.
-
- Sam Paik
-