One more HLSL trick

When implementing a quite complex pixel shader on pixel shader for multi-cascade shadows maps on shader model 2.0, I’d got a usual error message saying that “Arithmetic instruction limit of 64 exceeded“, so once again I have to find an instruction slot.

I had a code that tries to find the best shadow map for current pixel, something like:

//float2 map[] is a u/v pair; if it is "inside" the texture, I can use it
if (map[0].x < 0 || map[0].x > 1 || 
    map[0].y < 0 || map[0].y > 1)
{
  //...
}

This code was converted to:

//float2 map[] is a u/v pair; if it is "inside" the texture, I can use it
if( any (map[0]-saturate(map[0] ) ) )
{
  //...
}

This takes much less instructions, so now I have some free slots!

Advertisement

Tags: HLSL, optimizations