calculate flow consistency

[huagl]

Hi, I read your paper recently and found your code here. It's really a fantastic work. I have a question about the part of calculating flow consistency. `self.fwd_flow_diff_pyramid = [tf.abs(self.bwd2fwd_flow_pyramid[s] + self.fwd_full_flow_pyramid[s]) for s in range(opt.num_scales)]

self.bwd_flow_diff_pyramid = [tf.abs(self.fwd2bwd_flow_pyramid[s] + self.bwd_full_flow_pyramid[s]) for s in range(opt.num_scales)]` Does this mean to compute the full flow difference by forward-backward consistency check? Then, why the operation is '+' to calculate the difference, instead of '-' ?

[yzcjtr]

Hi @huagl, thanks for your interest. Actually, the forward and backward flows have different directions. That is, for point x1 in image1 and its correspondence x2 in image2, the forward flow is x2-x1 while the backward flow is x1-x2. Thus we adopt plus here.

[huagl]

Thanks for your reply! self.bwd2fwd_flow_pyramid = [flow_warp(self.bwd_full_flow_pyramid[s], self.fwd_full_flow_pyramid[s]) \ for s in range(opt.num_scales)] I asked question because I thought that self.bwd2fwd_flow_pyramid is the forward flow warped from the backward flow. Thus I thought it's reasonable to use '-'. So, the function 'flap_warp' doesn't convert backward flows into forward flows? Sorry to bother you a lot.

[yzcjtr]

No. bwd2fwd_flow actually means sampling backward flow according to forward flow.

[huagl]

Get it. Thanks for your kind reply.