Okay, so it has nothing to do with the orientation of the point planes. Having thought about it some more, I think this is a consequence of the reduction of su

Okay, so it has nothing to do with the orientation of the point planes. Having thought about it some more, I think this is a consequence of the reduction of surface area hit by the LIDAR rays, as the square of it's distance. Basically, the rays are cast in a spherical distribution (which has a surface area of 4pir^2). So the further out you go, the rays "capture" less of the environment, and you get the sort of sparse pixels at a distance. So those circles are just reductions in pixel density that are proportional to linear distance from the center of the LIDAR sphere. You can kind of see how depending on the distance to the building walls, the surrounding 'halo' of circular pixel density increases or decreases.