View Full Version : Volumetric fog/light beams

02-24-2002, 03:03 PM
hi, I've searched all over the net for 3 hours now. usually I'm good at weeding out tutorials or sample code or whatever else I can find would be useful. but on the topic of volumetric fog I can't find any decent documentation.

here's what I want to do:
simply make a couple of lights, spotlights, rotating from a central light "source". however, I want the volume of the light to be seen, as if it's shining through mist.

I've looked everywhere for anything on this subject, which you'd think would be well documented. I found a lot of broken links and demos of what I *wanted* to do but didn't include any source code on.

so anyway if anyone could help I'd really appreciate it.

02-25-2002, 01:17 AM
There are many ways to achieve a volumetric effect, choosing the best depends on waht you want, speed, photorealistic rendering...

A common way to do volumetric rendering is to render many slices of the shape you need (a cone I think), using the right texture and the right alpha.

This method it's quite slow if you don't implement it the right way.

Onther way could be using billboarded particles. (and light shafts looks more realistic if you have dust particles in them).

This could be fastest than the previous, but it doesn't look so good.

The last way it's to use models for light shafts, for example rendering blended concentric cones, with alpha = 1 in the edge and alpha = 0 in the base.

This is faster, but it doesn't look that good.

Hope this helps.

rIO.sK http://www.spinningkids.org/rio

02-25-2002, 10:04 AM
Do you know of any examples of each, or even one, of those different examples? The guesswork I'm doing with it doesn't seem to be working out.

like, for example, how would I make the base of a cone alpha=1 and the top alpha=0? can I do this using quadratics? i.e. gluSphere(...)?

02-27-2002, 12:33 AM
No, but building a cone isn't that difficult... http://www.opengl.org/discussion_boards/ubb/biggrin.gif

rIO.sK http://www.spinningkids.org/rio