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hehefan / P4Transformer

Implementation of the "Point 4D Transformer Networks for Spatio-Temporal Modeling in Point Cloud Videos" paper.

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Transfer of points to nearest frames

sheshap opened this issue · comments

commented

@hehefan

Can you please explain what does transfer of points to nearest frames mean?
how are they transferred? (I understand those anchor points are picked using Farthest point sampling)

image

Thanks in Advance.

commented

Hi,

Anchor points are picked using Farthest point sampling from anchor frames and then transferred (copied) to the nearest frames.

commented

@hehefan

Thanks for your reply.
Can you please elaborate a little more?

When we do Farthest Point Sampling (FPS) on anchor frames we know the indices in the array of 3D points.
Since points are unordered, how would copying to the nearest frames would help get FPSs points in those nearest frames?

or

By copying how do we know where the points are actually in 3D? (they could be anywhere in the next frame because they are unordered)

Thanks in advance.

commented

Hi @sheshap,

The method is point-based. Point coordinates are always maintained and used for position. When transferring a point to the nearest frames, both the point coordinate and feature are copied.