How can i fake underwater caustic rays ?

[andy gee]

Hi everybody

In Lightwave 3D I have a scene, where i want to create under water

caustic rays.

Now i know i could use volumetric lighting for this but i dont want

to wait 3 weeks for it to render.

Is there a way to fake this effect ?

Thanks

Andy Gee

[BazC]

Well you might fake it with luminous columns with an incidence based gradient on the transparency channel. Might take a lot of work to get it looking good though. I don't find volumetric lights so slow, you can add a texture to create multiple beams from one light, if you only use half a dozen spots for the beams it shouldn't take too long to render?

[Red_Oddity]

indeed, wobbly sheets and columns works very well...
check the making of pebble at the digital domain site to see how much you can fake with simple 3d and post

http://www.d2.com/links/comm/behindscenes/BHS1/bhs1.htm

(the d2 site seems to be a bit wonky, so here's the link to the movie file : http://www.d2.com/links/comm/behindscenes/BHS1/makingofpebl.mov)

[Wonderpup]

Splinegod posted a neat way to fake the underwater caustics on objects by using the underwater procedural in the luminosity channel with a gradient falloff in y (something like that) sounded really nice- worth a play anyway.

[loki74]

Splinegod posted a neat way to fake the underwater caustics on objects by using the underwater procedural in the luminosity channel with a gradient falloff in y (something like that) sounded really nice- worth a play anyway.

Wouldn't the gradient be in slope? :stumped: hmm.... Couldn't you also apply the texture to the light so it would cast that way?

At any rate, that would be for the cast caustics; I believe OP is referring to the "light-curtaining" effect caused by refracted light hitting microscopic particles or murkiness in the water (why else would a vlumetric light be needed?). Anyway I think the sheets/columns is a good idea, but you'll have to be careful about flying trough them...

[Wonderpup]

Hi loki74,

Quite right- slope's the thing. I realise I wasn't addressing the original question but I was thinking ahead- once you've got your light beams you'll need your other underwater stuff too right?

You could use a light, but I think that means rendering out the procedural first- which may be less flexible.

[duke]

Sorry to dig up an old thread but I'm trying to do the same thing right now. The underwater procedural doesn't quite cut it because of how it appears to come from a source. I remember there being a (free?) program that could spit out tileable, loopable image sequences of fake water caustics. It was included on a 3D world CD a long, long time ago.

[arsad]

http://www.lysator.liu.se/~kand/caustics/

hehe, have fun!

[erikals]

Used it, love it.

[McFilms]

That looks like a great program. Its a shame it can only be run on a PC...

*sniff* *sniff*