Many times in VFX work the need arises to quickly calculate the intersection of two or more objects and then do stuff with the resultant intersecting regions. I was asked this question from one of the many clever Houdini users where a simple example was worked up. The idea is to take any objects loaded from disk (cached from an RBD simulation or whatever) and then generate dust from the areas where the objects would get close or interpenetrate.
Let's step back a bit and set some reasonable initial criteria and work up a simple SOP node network. When calculating the intersection between two objects, the objects should be somewhat manifold meaning a closed shape that can be used to build a proper volume. With that single restriction (really not a restriction as you can generate volumes from anything: points, curves/lines, flat planes, etc), you can use a few SOPs including some new to Houdini 11 and a clever technique to isolate intersecting regions between any number of objects.
Three examples will be worked up from a simple two object intersection, multiple object intersection and finally calculating intersections from an RBD simulation. First on the list is to look at a simple method to detect overlapping regions of multiple objects.