Derivative Texture Sample Cost?

[Ludvig]

I find this answer very informative

Procedural normals for threshold animations

Yeah, people are always scared of derivatives, but they are nearly free. Certainly cheaper than resampling the texture 2 or 3 more times. Like @mattorialist mentioned it’s using data that’s already been calculated, a ddx or ddy is effectively just the cost of a single subtraction, but shared between 4 pixels. Even fwidth is just two subtraction and an add, again shared between 4 pixels. For to reduce aliasing from using derivatives you can try using ddx_fine instead. Since ddx is calculated for…