How to quantize surface normals
问题 I am trying to quantize surface normals into let's say 8 bins. For example, when computing features like HOG to quantize 2D gradients [x,y] into 8 bins we just take the angle with the y plane i.e. arctan(y/x) which will give us an angle between 0-360. My question is, given a 3D direction [x,y,z] , a surface normal in this case, how can we histogram it in a similar way? Do we just project onto one plane and use that angle i.e. the dot product of [x,y,z] and [0,1,0] for example? Thanks EDIT I