Would it be usefull to pre-sort the points in some gpu relatd way?
I don’t think you need to do that for 15 millions of points.
VTK will not have a huge gain if you do that as the vtk mapper cannot reuse it directly, if you still want to do that you’ll need to write your own point cloud mapper with a first pass of depth sorting
Note that this approach was already done in another vtk based app named F3D for gaussian splatting support, here is the related mapper: f3d/vtkext/private/module/vtkF3DPointSplatMapper.h at master · f3d-app/f3d · GitHub