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hardware bumpmapping

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nitzan    108
What exactly is being done on the hardware in "hardware bumpmapping" aside from multi-texturing ? It seems like the majority of the calculations are cpu rather then graphic card based. Thanks, Nitzan

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Corrail    133
No, the bump-calculation is normaly done in the Texture Environment or Pixel Shader (for new graphic cards). Normally you do a dot product using the normal map and the normalized (using a normalization cube map) light vector (or view vector, whatever you want).
Beside this dot product there is (depending which parts of the lighting equation you want to implement) the attenuation and the specular "power" operation. These can be done in software or hardware. The specular "power" operation is quite difficult to realize in non-pixel shader systems (I use NV_blend_square and draw the specular component a few times depending on the shininess).
The preperation (Lightvector or viewvector from object space to tangent space) can be done fully in hardware using vertex programs or texture matrices. You surely can do that in software but if your graphic cards supports vertex programs (GeForce 1 and up in software emulation, GeForce 3 and up in true hardware or Radeon 8500 and up int ture hardware) use these.


"If it looks good, it is good computer graphics"
"If it looks like computer graphics, it is bad computer graphics"


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