View Full Version : Volumetric Light+ Projected Image

06-26-2005, 05:43 PM
I'm playing around with volumetric lights and image projection in order to get the underwater effect for my trilobite animation. I've generated a sequence of images using the amazing Caustics Generator (http://www.lysator.liu.se/~kand/caustics/) and have been projecting it. I've noticed that when the light is just volumetric, the beams are very apparent, but when I turn on projection, in order to have the light play across the objects underwater, the beams become much more faint. I'm going to be rendering these things as separate passes, but I'm curious as to why this might occur.

06-28-2005, 01:29 PM
Nice link! Very nice underwater effects!

This image was generated just using the AVI file from their website (masked with a circular mask) as a projection image on a spotlight with a 1024 shadow map and simply checking the Volumetrics box. The rays look fantastic to me.

Maybe adjust the contrast/brightness of the generated imagery? Maybe the sequence(s) you're generating are too dark?


06-28-2005, 04:54 PM
I think that's it. The image I was rendering was just a ball moving through the beams in a blank, black background (say THAT three times, fast!). It's as though LW optimized the scene for contrast on the ball, darkening the rest.

Your render looks cool, by the way. Reminds me of a Painter piece I did a while back.

06-30-2005, 12:38 AM
Something else you can try:
Load a blank black or white image into the image editor.
Apply the textured filter to the blank image and set it up with something like the underwater procedural or somthing similar. You can also animate the procedural from the textured filter panel. Project the blank image thru a spotlight and it will also now project the procedural.


06-30-2005, 12:44 AM
Great tip! Thanks!
I also use Cinema 4D, and it allows you to assign textures to lights just as you would objects, and I've always wondered if there was a way to let LW do the same thing, but my experiments with goboes and transparency were less than spectacular....

06-30-2005, 01:01 AM
This trick also works with UV maps. You can apply the blank image to a UV map with the procedural applied to the blank image in the same way. Youll now be able to see the procedural in Opengl and adjust the UVs on the procedural. This works in model as well :)

andy gee
09-23-2005, 05:46 AM
Hi this i just the effect im after

i can acheiveths technique but, with a spot light it doesnt cover my whole scene

would le to know how this was done


Andy Gee

09-23-2005, 06:09 AM
If it's just because your spotlight beam is too narrow, move the light back so you get more spread. Make the texture a little smaller if you have to, and adjust the falloff or disable it entirely so that the beams reach to where you need them to. If it's some other cause, I'd need to know more.

andy gee
09-23-2005, 06:55 AM

well i want the caustic rays to all over my scene because the camera moves a bit,

i want to be able to see the caustic rays were ever i point the camera at the moment i

can see the effect but i some times see the actual cone shape of the light, instead of

continuous caustic rays ! so how can i sort this out ?

Cheers Andy Gee

09-23-2005, 07:20 AM
I'd just really move the light back so that the radius of the cone down where your camera is is bigger than the fog fall-off radius you have set. That way, no matter which way you look, the beams will go off into the distance and you won't see any edges. You could also widen the cone a little, but I rarely go beyond about 30 degrees because that leads to unnatural splaying of the light. Just move it far enough away and that'll solve the problem.

09-23-2005, 07:22 AM
Oh, yeah, you have to keep the texture plane close to the camera when you move it, too (parent it), otherwise, while the spread of the beam will get bigger, your texture will just be a little spot in there.