samizdatco/arbor — pull request #30 by pcottle (2012-05-26 22:39:23+00:00)
Title: Use Mass in Velocity Verlet integration to restore drag-and-drop behavior

As per our earlier discussion, I realized that the mass of a particular particle can change in time; the mass of all the particles may not be the same as well, so this required new code to deal with changing mass.

I also changed the physics to cache the "old mass," meaning we can now cache the old acceleration and get even better dynamic behavior. The atlas demo now shows off this new mass changing behavior (and dragging and dropping); frankly I think it looks quite nice!