Basically, I have two objects represented by 3D surface point clouds. Object 1, lets say, is a blob of clay. Object 2 is the same blob of clay, but chunks of clay have been added or removed.
So I have these two point clouds, and they have already been registered into the same coordinate space. Now, I need to answer the question: which parts of the 1st blob remained intact in the 2nd, and which parts are new?
Here is an example. The first picture shows an example of the "1st blob of clay." Note the small cone protruding from the clay. The 2nd picture shows the "2nd blob of clay," in red, registered to the 1st blob of clay. The 2nd blob of clay is exactly the same as the 1st blob of clay, except the 2nd blob does not contain the protruding cone.
This is precisely what I would like to know. I would like to know that the 2nd blob is the same as the 1st blob, except for the cone. This is an easy example, but I have more complex secondary blobs that have both added and removed portions. I just want to know which parts of the secondary blob are leftover from the 1st blob.