Collide force doesn't handle identical initial positions well about d3-force HOT 7 OPEN

Sorry I don't know why I had never pushed this branch from my laptop. Now PR #214.

from d3-force.

Respecting user-defined initial positions seems like the expected behavior. In fact, adding jitter to user-defined initial positions might cause problems in some cases (for example if you need all the initial x values to be exactly 0). A possibility might be to define a force that jitters positions on initialization, but I don't see how this would be easier to use than jittering the initial positions?

from d3-force.

I guess my suggestion is less that initial positions should be jittered (that was just my own solution and I agree that overriding users' explicit intentions would not be good) and more that the direction of the force applied by forceCollide should be. It seems to send all points outward along a common axis, rather than sending them in all directions as I would expect. I suppose there must already be some way of deciding which way to send the points in this case, but it seems to apply to all points with the shared position rather than picking a random direction separately for each.

Anyway, just a friendly suggestion. Thanks for your contributions to such an awesome library.

from d3-force.

It should already be the case

oh, I see… it seems to be because, once the two first dots have been "randomly" separated, the other coincident points are not anymore within 0 of those points, and so the force is in the direction set by the first random jitter. A bug!

from d3-force.

Oh wow nice catch @Fil ! That's subtle.

from d3-force.

I have a fix here https://observablehq.com/d/dd1bcd29c2b1b850; it breaks the symmetry of the original solution for 2 coincident nodes, which is not a requirement but was kinda nice.

from d3-force.

Any update on this? I just realized that it's been nearly a year. I actually have a few other use-cases now were it would be really nice to have this resolved. Happy to try and create a pull request if it helps!

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