Hi all.

Have a houdini a some ways for creating multicolored (sorri, i don`t know right name for this) volumes for post color-correction ?

Or how professionals make this ? My skill in this is “zero”. But, if for example, i have troubles with lighting in 3D scene setup (or it very long time to render with shadows) - how can i do this trick for post-composition?

And, please, if someone know, where i can read about this ? I`m only see this technique in Digital Domain demos… No learning info.

How can i create this effect in houdini ? This possible ?

p.s.

Sorry, i mean post-lighting setup. Or lighting and color correction of volumetric effect.

That technique is only three different lights in different positions (for example key, fill and rim), each one with red, blue or green color. Then in comp you can control the intensity of each light.
It's pretty simple, actually

Wow wow wow! MiguelPerez thanks!
very interesting, and only one question -

This three lights are generate shadows or not ? Without shadows volumes look pretty flat ..

?

Hm. Answer not needed.
Of course - is not. Only one shadow is needed.

Three lights can be a bit limiting and of course only works if you have monochrome (i.e. grey) volumes.

The more advanced solution to this is to make your own Illuminance loop that breaks out each light to its own deep raster image or channel. There is a thread on Odforce (somewhere) detailing this, though it's not for volumes specifically.

Basically, a Volume shader has two components. One calculates the density of the volume, and the other calculates the lighting on the volume. The density is of course the same for each light, so that is just calculated once. The lighting is calculated for each light. The trick is to make sure you multiple the lighting calculations by the density for each light otherwise it looks completely wrong (blocky and ugly).

Cheers,

Peter B

Thanks pbowmar, i try to work with it. In some cases start volumetrics render again after slightly light tuning - is insane idea. I try now all methods - with 3 lights for gray-colored volumes, and, of course, another trick - as you say.

big thanks..