How do I combine registration with clustering?

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Hi,

I am using the kinect and searching for one or more objects on a table. That works fine for me. Now I want to change the position of the kinect i.e. move it partly around the object and again search the objects lying on the table and then combine both object point clouds. The result of that should be that I get more point of an object (from different viewpoints) or in other word i will just remember the points I saw before. Is there a way to do that with pcl::registration? And do I have to use the registration algorithms before I cluster the objects or am I able to do it after clustering with only the few points I get from an object.

Thanks Stefan