When I choose points from two overlapping cloud points, how can I just choose the upper one?

[yjf27281181]

Hi Daniel,
I met a very thorny problem when I used cloudcompare.
When I choose or cut cloud points, it seems that cloud compare would choose all points that is in the polygon drawn by users. However, in most cases, I just want to choose those points which is not covered. In other words, I want choose the upper one which is in the polygon from two overlaying layer. Does there have existing tools to let me do this. If there does not have, do you have any advises to help me implement this function?

[daniel]

Actually the Interactive Segmentation tool only selects points from the selected clouds. So if you already know which cloud is above the other one, you just have to select the right one.

Otherwise, if both clouds are 'mixed', I'm not sure how to do this properly... You could maybe try to use OpenGL to detect if a point is above the others, but it won't be easy to do it efficiently. And the result will depend on the current zoom as points won't have the same size depending on how close you look at them (that's always the same issue with point clouds ;).

Anyway, everything happens in the ccGraphicalSegmentationTool.cpp file, and more specifically in the ccGraphicalSegmentationTool::segment method. In this method you have access to the 3D view, and to the selected clouds.