   HLSL - Multiple effects on GPU
  Having already asked 2 HLSL questions no one can anwer, I am going for three.I have already bumped into the 64 instruction slot max for PS_2_0.  So, I now have different functions defined for Blinn versus Phong shading.  It does the calculation for up to 4 directional lights.  I want to add bump mapping and the ability to have different kind of lights, like a spot light, that has even more calculations to perform.I am realizing that there ain't no way I am going to be able to do all of this in the pixel shader.  Every sample I have ever seen just uses one light.  So I am wondering how game developers deal with situations where they want to have multiple lights, use a pixel shader technique (like Phong), and do bump mapping, where you would need to apply the TNB matrix to each light vector and pass it along to the pixel shader.  Do they end up falling back to vertex lighting when they want mulitple effects?  It seems that until PS_3_0 the VS has plenty of room for stuff, but the PS is too limited for anything substantial.TIA.   
  For a large number of reasons (shadowing algorithms probably being the most important among them), most games do not run more than one light per pass.   ;  You might want to look at deffered shading.   