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View Full Version : Need help w/Volumetric, please



Pinzmon
06-27-2003, 11:47 AM
I'm having real trouble trying to make a volumetric light look right. I have a point light with volumetrics enabled inside this head with a slice missing at the forehead level. It generates the volumetric effect I want out of the slice, but it also renders this dark shadow around the whole object. (See picture)

http://www.haynie.org/files/volprob.jpg

The head surface is double sided, and set to cast and receive shadows. The white backdrop is a sphere that is set to be unseen by rays, and not cast or receive shadows. I've also tried it with just a white backdrop, and it still shows this shadow area.

Any and all help getting this right is appreciated.

pinz

06-28-2003, 10:14 AM
A quick burst in demo mode ('cause I left my dongle at work) shows me that the effect you wish you werent experiencing is produced only when you turn 'opacity' up above zero percent with some darkish volumetric settings.
Put it this way, you can acheive the effect you are looking for - the light comong out through the split - just by using a texture in the volumetric light.
Then what you are asking LW to do is pretend that the 'medium' - fog, particles, droplets or whatever - is only existing in the volume defined by the light beam.
If you want a more 'real world' effect, then you set a value for opacity, whereupon lightwave assumes that the 'medium' is actually filling the whole volume defined by the falloff settings of the light, not just within the unshadowed areas of its beam.

Generally speaking I would recommend setting up a specific volumetric light setting in a very simple test scene, starting from almost scratch unless you are sure of what you are doing &storing the settings in a preset library as you tweak it. As you have found, some of the settings do not do what common sense suggests they might, and applying common sense does not therefor lead you to the culprit.

Pinzmon
06-28-2003, 11:32 AM
Absolutely - thank you very much. It now does exactly what I was looking for.

Pinz.