Using HILO textures with Cg

OpenGL OpenGL: Advanced Coding
1

Hi! Does anyone know how to use HILO textures for bumpmapping with Cg fragment programs?
I might be missing something here, but I can’t get it to work on the FP20 profile. Reading the texture’s rgb components just gives me 0’s.
Thanks!

2

With the fp20 profile, HILO textures can only be used by the DOT_PRODUCT* texture shader operations (i.e dot product 2d, dot product reflect, etc…). You can’t directly lookup into a HILO texture using tex2D().

3

In the NV_register_combiners extension (which the Cg fp20 profile is based on), you can’t use a HILO texel. You can only use them in certain texture shader operations.

In the NV_fragment_program extension (basis of the Cg fp30 profile), you can read and do math on a HILO texture. The same will be true using ARB_fragment_program (Cg arbfp profile) if you have a HILO texture.