While I was preparing a guest lecture, I created the following example of a SWI Prolog external predicate interfacing into the Point Cloud Library (PCL). A CCalc (action language interpreter built with SWI Prolog) example is provided also. The readme should do the explaining.
The toy example given is multi-robot path planning with obstacles obtained by finding the ground plane and then counting points above the plane (the example uses cropped Kinect data from one of the PCL sample files).