[osg-users] Computing Normals for Drawables

Jean-Sébastien Guay jean-sebastien.guay at cm-labs.com
Fri Nov 6 11:31:42 PST 2009

Hi Simon,

> I'm not familiar enough with shaders though to say it's actually
> possible to do that., but it looks doable.

Totally, it's good idea. It's actually reminiscent of spherical 
harmonics, but in reverse (instead of sampling illumination in all 
directions on a sphere, you're choosing the direction that best 
represents the normal).

The only thing is that the smallest unit for per-vertex attributes is a 
32-bit float, so using a byte doesn't necessarily save anything over a 
normal stored as theta+phi angles quantized to two half-floats, and that 
way you don't need the lookup table of normals to index into.

But it's a good idea, I agree, as long as you can accept a slight loss 
in lighting quality because of approximated normals (will probably show 
up as banding on smooth surfaces).

Jean-Sebastien Guay    jean-sebastien.guay at cm-labs.com

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