No, I mean (non-)differentiable, although differentiable non-continuous is also not useful. If you scanned every pixel for every polygon and discretely determin

No, I mean (non-)differentiable, although differentiable non-continuous is also not useful. If you scanned every pixel for every polygon and discretely determined whether it was inside or outside that would be as you describe, but that's rarely the case. Take a look at the typical line drawing algorithm[0] - it procedurally determines which pixels to draw as part of the line. Without modification such algorithms don't give you derivatives of how each pixel depends on the shape parameters. [0] https://en.m.wikipedia.org/wiki/Bresenham%27s_line_algorithm https://en.m.wikipedia.org/wiki/Bresenham%27s_line_algorithm