I am trying to implament this paper in threejs, and in order to do so I need to get the direction that the arrows are going at each pixel here in screen space. The arrows are just visuals, this isn’t going to rely on them. They go along the positive y axis of the UV coordinates. I am attempting to calculate a orientation map in the fragment shader so that I can feed it into the non-photorealistic post processor. Ignore the hall of mirrors hell going on in the background.
I have tried converting [0,1,0] from tangent space to world space and then projecting that onto the view plane, which did not work. I also tried getting the dF/dx and dF/dy of the uv coordinates, which also did not work.