Tons of problems trying to simulate simple rope without elasticity

[josemendez]

paperclip is not tightly fixed to the bottom rope particle. I also tried to add by 1 control point to each side of the rope, just to see, will it "help" to hold paperclip or not, but this didn't work. Here is example

Pin constraints are still constraints. This means that if they don't fully converge at the end of the frame, the condition imposed by them might not hold perfectly. As in any iterative solver, this is exacerbated by large mass ratios, and improved by using smaller time steps or more iterations.

You can either use more substeps, spend extra iterations on pin constraints alone, or reduce the mass of the clip. This should help completely close the gap.

I found that if paperclip hit the trigger collider (I need it in my case to detect the TriggerEnter event with another object) each frame. This means OnTriggerEnter and OnTriggerExit are called even when paper visually doesn't leave the collider area. I assume this is because the interpolations, but is there a way to solve it?

Not sure what you mean. Triggers are part of Unity, Obi's solver interpolation has no effect on them. If you're referring to rigidbody interpolation, then yes this is to be expected: interpolation derives rendering state from physical state: objects are drawn where they should be according to render time, but as far as the physics engine goes (this includes triggers) they're located elsewhere since simulation time != render time. Same for extrapolation. I don't think this can be prevented.

I updated your sample scene adding real size objects and added TriggerDebugger component so you can get easy what do I mean in #2. Please have a look, I hope I may make it work finally as expected.

I can't see any links to the updated scene. Can you share it so that I may take a look?