Re: [Algorithms] Water Effects

[Charles B. <cb...@cb...>]

The outcast home page has a description of their water
technique, as well as a lot of other cool tricks. 
Unfortunately, their algorithms only work with their
software renderer for their voxel engine.

The recent "Game Programming Gems" book has a little
article by some ATI guys (Jason Mitchell + some guy)
on 3d water effects.  Basically, they just wiggle
some verts with trig functions, and then do some nice
UV mapping for reflection and refraction simulation.

The water in Halo has been talked about alot.  It would
be nice if someone wrote up a summary of all the tricks
for water (I've been meaning to).  (For example, it's
well known that "particles can be used to simulate the
specular flicker", but I've never seen a good write-up
of that technique).

My basic summar of how to do water is to start with
reflection, using EMBM or environment mapping or something.
Refraction is pretty irrelevant for large bodies of
water, you basically can't see into them.  Once you've got
the water base-textured with the reflection map (with uv's
wiggled to simulate waves) you need to lay some fake
speculars on.  I would do this with a black and white texture.
You simply tile it, and wiggle the uv's to make it irregular,
and lay it down as an additive pass.  Then, rotate the uv's
and wiggle them differently and lay down another additive pass.
The combinatin of the two passes, both wiggled a bit, is
that you break up the regular tiling pattern that afflicts
most water.  Also, if you shift the uvs of both passes you get
a nice irregular wave effect.

Of course, to simulate the height of the water, you just do the
old 2d wave effect and make a mesh from it.

A bit rushed and incoherent, but hopefully you get the idea...

At 10:34 AM 8/26/00 -0700, you wrote:
>Hi,
>
>Does anyone know how the fantastic water effect is done in Outcast?  Is
>there any good 3D water-effect tutorial on the web?  (I know GameDev has
>one, but only 2D.)
>
>Thank you for the help,
>
>Pai-Hung Chen
>
>
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-------------------------------------------------------
Charles Bloom    cb...@cb...    http://www.cbloom.com