edwardzhou130 / PolarSeg

Implementation for PolarNet: An Improved Grid Representation for Online LiDAR Point Clouds Semantic Segmentation (CVPR 2020)
BSD 3-Clause "New" or "Revised" License
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Circular convolutions and infering back to 3D? #52

Open JohanBergius opened 2 years ago

JohanBergius commented 2 years ago

Hi, Author. Could you please explain or give me directions to where I can better understand the approach of Circular convolutions (ring CNN). I would also like to understand better how your was able to reverse back to the original 3D space after going removing the Z dimension!

YangZhang4065 commented 2 years ago

Hi Johan, sorry about the late reply. For circular padding, please refer to my latest reply here: https://github.com/edwardzhou130/PolarSeg/issues/46#issuecomment-1188624027 Reversing back to 3D space is actually quite easy. At the last layer of our neural network, we predict a 2D feature map of size HxWxZ for each scan/ BEV image. H and W is the height and width of the BEV map. Z is the feature dimension which equals to the number of semantic segmentation classes * the number of cells you want to have per each pillar (we used 32, but you can use whatever you want). Then you can reshape it to H x W x num_class x num_voxel_per_pillar and treat this reshaped feature map as semantic segmentation prediction on the 3D voxel level.