ObiColliders and Procedural Load

[josemendez]

Well, OK, I suppose I can give up at this point and stick with the rope solution I had before.

I'd read about this problem as it relates to Obi before, but I figured it could be bypassed because mass ratio is always mentioned in the same sentence. I do not require the rope to have low mass. When you crank up the weight of the rope it starts to behave more like a heavy cable, which is exactly what you'd expect when lifting something really heavy. Adjusting the mass of the rope to keep the mass ratio within the simulation limit is how I got my current rope solution to work. But I guess it doesn't work with Obi.

Thanks,

Jon

Hi Jon,

Obi has exactly the same limitations as PhysX when it comes to mass ratios, since they are both iterative solvers and use integrators of the same order. For the same mass ratio / constraint chain length / iteration count / step length combination, both behave the same way. The difference is that PhysX (Unity's engine) becomes unstable (jittering, velocity spikes and the possibility of a crash) when the rope is overstretched, and Obi does not (things just stretch).

Btw, cranking up the weight of the rope yields exactly the same dynamics (same visual behavior) as lowering the mass of the load. So why do you need the load to be so heavy, if you can afford the rope to be very heavy too? Having a low mass ratio (similar rope weight and load weight), will make the load look light because it will not tense the rope quick enough.

That being said, I still believe that using an iterative solver for this is a bad idea. Found some AgXDynamics bindings for Unity, it's an engineering grade simulator that features both direct and iterative solvers. You might want to give it a run: https://github.com/Algoryx/AGXUnity