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Dragon89
02-24-2007, 02:59 AM
anyone know of a way to do underwater lightshafts (god rays) on a bumpmapped water surface...

Mikkel Gjoel
02-24-2007, 08:18 AM
How about a bunch of additive billboards for the god-rays, and... uhm... bumpmapping for the bumpmapped water surface? :D

Dragon89
02-24-2007, 09:40 AM
sounds like an idea... but how should i do the billboards? should i have several long triangles into the water and then set some texture on them... how do i get some good movement on them? should i use some kind of radial blur?

Jan
02-24-2007, 12:56 PM
How about just trying it out?

remdul
02-24-2007, 01:57 PM
How about a more constructive comment?


Originally posted by Dragon89:
but how should i do the billboards? should i have several long triangles into the water and then set some texture on them... how do i get some good movement on them? should i use some kind of radial blur? You should try textured, axis aligned billboards. Here's a link with more info + some code:

http://home.planet.nl/~buijs512/articles/billboards/

Use alpha transparancy to fade out the rays when the viewer gets to close to the line segment, or the viewing direction is almost parallel to the line.

Another method is by placing several, ~50% overlapping, view aligned billboards (or particles) along the rays path (make the billboards fainter as they go deeper. Also use transparancy to fade out the billboards when you get to close.
With this method you will also see the ray when the viewer is in the light's path. I saw this in Call of Duty (light thru church window effect) and it worked surprisingly well.

As for animation, use a sine wave to dim and brighten the color alpha over time (different, unique phase for each ray). If the surface of the water is moving, just translate the entire ray vertically.

Dragon89
02-25-2007, 12:33 AM
thx.. ill try that