Why are dFdx/ddx and dFdy/ddy 2 dimension variables when quering a 2d texture?

Question

I cannot seem to understand this, shouldn\'t the derivative/change along the U or V coordinate in a 2d texture/array be single dimension variable as we are checking it only alon

Answer 1

You are computing the derivative of a variable (such as the uv-coordinate of a texture) with respect to the screenspace in either the x or y direction. Or in other words you could say that the function answer the question: "what change will happend to this variable when I move one pixel to [the left]/[up]".