NVlabs / PWC-Net

PWC-Net: CNNs for Optical Flow Using Pyramid, Warping, and Cost Volume, CVPR 2018 (Oral)
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Question on flow normalize #88

Open ghost opened 5 years ago

ghost commented 5 years ago

Hello, Could I ask why you normalize the flow by vgrid[:,0,:,:] = 2.0*vgrid[:,0,:,:].clone() / max(W-1,1)-1.0 in the warping function?

Due to minus value in flow, the vgrid could also have minus and then the result of that line could be less then -1. Isnt that out of purposed vgrid range [-1, 1]?

Can we assume that vgrid == sum(grid, flow) always stay larger than 0?