Hi all, I am in the middle of writing a piece of scientific software which needs to know where a particle at (x,y,z) is in relation to a 3-D model. This part of the code needs to know what object (x,y,z) is inside, and which objects are next to that object containing the particle for when the particle exits the object with (x,y,z). Are there any easy algorithms or libraries to do this? I was looking at something like CGAL, but that only seems to have a 2-D point-in-polygon routine, and not a 3-d one. I'd love to figure this out independently, but unfortunately doing so would double the work required for my thesis, and it is not even a required element, just something i decided not to simplify away. Any help is appreciated!