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rirad
07-24-2003, 02:53 PM
I have a small question about inverse volumetrics. I would like to simulate the presence of a opalescent medium between two geometries (For example inside a sphere). My idea was to use inverse volumetrics to do the trick. I made a scene like this:

- top inverse volumetric light spot (facing down and containing a transparency map with noice)
- below the light: a plane (normals facing towards the light)
- below the plane: another plane (normals facing away of the light)

After the light rays pass the first plane, the inverse volumetrics are created. Now I hoped the second plane would block the inverse volumetrics light beam (making it appear as if the volume inbetween the two planes is opalascent) but unfortunately it doesn't.
I tried reversing normals and light exclusion settings.

Does anyone know a method to block inverse volumetric light beams by geometry?

Thanks, rirad (also posted at postforum)
rirad
07-24-2003, 03:04 PM
The question still stands but I found another way to get the effect I wanted.
Put a volumetric fog on a sphere does exactly what I want.
I am still interested in an answer to my first question though.
Thanks anyway.
rirad
07-24-2003, 03:22 PM
Now I have another problem also. I can't seem to exclude lights to the object that has the fog shader (volumetric fog, no decrease fog type) applied. I put the object in the exclusion list of 2 out of 3 lights (so the third light would eluminate the fog) but when I render it, it is overexposed. If I disable the 2 lights, I obtain the effect I am looking for.
Can anyone confirm this. Is it a bug of the fog shader?
rirad
07-24-2003, 04:31 PM
I am having fun answering my own guestions :)
Apperently, the volumetric fog shader acounts all light sources (acording to the manual, so sorry for asking).
That is a pitty however, if a scene only uses one light source it works great. Most scenes use more lights so you lose a lot of control thisway and the volumetric light effect is easily blown out.
Does anyone know of other alternatives? I am out of options.
JamesMK
07-24-2003, 06:05 PM
If you attenuate your lights carefully, you should be able to control some of the overexposure. Not the same as exclusion, of course, but it might be worth looking into.
flingster
07-25-2003, 10:43 AM
interesting question....would like to know peoples thoughts and experiments on this one also..haven't a clue as to a solution though sorry!

any chance you can post a result rirad?
:thumbsup:
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