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Water normal maps

Started by MGB Feb 27, 2007 at 4:56 PM 1 reply 1.4k views

Original Post

Feb 27, 2007 at 4:56 PM

Hi all, I'm trying to do ye olde water via (GLSL) shaders, and having 'fun' with the normal map. From the examples I've looked at, a normal is read from the normal map texture and then some funny things are done to it, like:


  surfNorm = surfNorm * 2.0 - 1;

I think this is transforming the range of the normal (i.e. from 0..1 to -1..1)? Thing is, applying fresnel to this and visualising gives totally wrong results: (red is 'refracted', blue is 'reflected')

I suspect the normals are the problem, because using an up-vector normal + fresnel gives a correct image:

Umm, so any ideas on how I should manipulate the water normal map?

jamesw

Feb 27, 2007 at 10:13 PM

Make sure your up vector in whatever space you are doing the calculations (tangent or world most likely) matches the up vector in the normal map. So for example if z is up you should see mostly blue in the normal map.

MGB

Author

MGB

Feb 28, 2007 at 3:42 AM

...and funnily enough, my normal map is mostly... blue!
Doh, that'll be it then - I'll swap the g & b - cheers jamesw.

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