View Full Version : god rays

08 August 2003, 03:38 AM
hey guys,
wondering if anyone has a clever way to mimic underwater god rays without using volume fog on a light. i'm thinking more towards simple geometry and transparency maps... i just need a push in the right direction.
cheers, tav

Son of Octropos
08 August 2003, 10:57 PM
Boy does THIS take me back . . . .

You can use a gradient that fades from nearly opaque at the top to fully transparent at the bottom (you can use a simple greyscale gradient to do this if you package supports Transparency maps, alternately if you have access to gradients in your materials editor it works that way too). You can apply this to a triangular/trapezoidal piece of geometry.

For rays with volume, same idea- just apply your gradient to a cone or what have you

Back before I got hold of volumetrics, I found making the opaque part of the gradient a slightly lighter shade of the main light color gave reasonable results. . .

Depending on how your renderer calculates such things, these may be quite a bit faster to render, too.

Hope it helps!

08 August 2003, 11:21 PM
thanks Son of,
that helps... i think i can use a ramp in the example you were giving. this is something i want to animate to give the apearance of light moving through water. my thoughts to get this effect have been to key the ramp at different opacity values on a cycle (with a texture on the light ofcourse). think this will work?

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