Background

So here's the scenario. I have a baseUV that I reuse to sample several base maps (eg. base color, material, normal map, height map, etc). When I apply Parallax Occlusion Mapping, I have to calculate ddx(baseUV) and ddy(baseUV) to use before sampling the height map in a while loop.

Questions

1. Is it more efficient for me to reuse that ddx(baseUV) and ddy(baseUV) with tex2Dgrad() to sample all my base maps?
2. Is it better to just use tex2D() at this point, especially after applying offsets from POM?

Thanks.

Okay. Thank you for your assistance. ;)

Historically, tex2Dgrad is slower than a normal tex2D even if they have equivalent results. Explicitly specifying gradients potentially requires that the shader core send quite a bit more per-thread data (6 floats vs 2 floats for the 2D case), and on some older GPU's this caused a performance penalty. I'm not sure if it's still slower on newer GPU's, but personally I would still avoid it in order to avoid unneeded register pressure.