For creating runtime tight knot

[josemendez]

Hi,

     I was working on the obi rope to tie a knot,How to make a tight knot without collapsing with rope thickness under 0.2. We are trying to simulate suture threads. What sort of values and parameters would be ideal for this. I tried the self-collisions and different collision iterations, particle iterations but it didn't solve my purpose.

Regards.

Hi chanddu,

Ideal settings for this are high distance constraint iteration count (ObiSolver->Distance Constraint Parameters->iterations), and high particle collision iteration count. However, given that Obi is an iterative solver, there will always be a limit at which constraints won't be able to be perfectly met.

So no matter how much you increase these, there will be a threshold force that, once surpassed, will cause the knots to undo. Best approach for this is clamping the amount of force that can be exerted by the user by pulling the rope.

Also for suture threads you'll most likely need a type of constraint usually known as a "sliding" constraint. They allow to constraint the rope particles to pass trough a point in space, which is essential to accurately simulate sutures. Obi does not provide these, as they are pretty much used just for this very specific scenario.