Collide force doesn't handle identical initial positions well #199
Description
I'm working on a fixed force layout with collision and X and Y positioning. It's being rendered by React, and so I'm trying to optimize and speed up the force layout to reduce the expense of the simulation as my component may be resized, panned, and thus rerendered/resimulated quite often.
I found that initializing the node positions with the x and y properties greatly reduces the number of ticks needed to get the layout looking the way I want it. But it also causes some problems where the initial position is the same for several points, as in this map where I'm trying to cluster points around polygon centroids.
With another 40-50 ticks, it will settle down into something like this which is what I expect. (Possibly just due to floating point error?)
I can get the same effect with a shorter simulation by applying a deterministic (seeded) random jitter to the initial positions, but I thought it would be nice if D3 could handle this itself similar to the way the phyllotaxis arrangement around 0,0 does this for the default initial positions.