Hidden Point Removal (plugin)
qHPR stands for "Hidden Point Removal" and is an implementation of the method proposed by S. Katz et al. in their article titled 'Direct Visibility of Point Sets'.
The algorithm filters out the points of a cloud that wouldn't be seen (by the current 3D camera) if the cloud was a closed surface. Therefore it tries to remove the points that should be hidden in the current viewport configuration.
Therefore, if you use this tool for a scientific publication, please cite the author before citing CloudCompare (which is also very good but less important in this particular case ;).
This algorithm only works if the projection mode of the 3D view in which the selected cloud is displayed in is perspective.
The user has to set the octree level at which the cloud will be approximated (the greater the finer the result will be but also the longer the computation will take).
In the latest versions of CloudCompare the plugin outputs a new cloud containing the visible points only.