Help Rope Tunnels Through Even With Continuous Surface Collisions

[Rangasoup]

Hi,

What's the mass of the rope, and the mass of the object?

Also, could you share your full solver constraint settings? You're using 8 distance constraint iterations at 160% relaxation, if your collision constraints - not visible in your screenshot - have less iterations you're basically telling the solver "the rope not stretching is a lot more important that the rope missing collisions, so it's fine if you ignore collisions as long as the rope doesn't stretch".

Typically your iterations should all be set to 1 and 100% relaxation, then crank up your updater's substeps for better simulation quality. Then fine-tune constraint iteration counts if there's a specific constraint type that you want to spend more resources on. The manual contains a very in-depth explanation of substeps/iterations and how they affect the results: http://obi.virtualmethodstudio.com/manua...gence.html

kind regards,

Thank you for the quick reply.

The rope has a mass of 2 (Are the units per particle? Does that mean resolution and width affect the rope's kg/m?) and the object 1440, but tested with lower mass ratios as well, brought it down to 6 with no fix.



I was using 6 substeps and all the other constraints were at 1 iteration. I bumped the collision constraints up to the same as the distance constraints and am using 100% relaxation now but it does not fix the problem.

I had tried trading iterations for substeps but 6 is about the limit before performance goes < 60fps. Tried up to 42 substeps with 1 iters anyway but it does not fix it either.

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How is collision resolved for SDF colliders? When continuous collision creates that velocity-based bounding box, are nearest contact points predicted, or does it only add more colliders to check for the broad-phase? I am wondering if the particle goes deep enough into the SDF, and if collision pushes it out in direction of the gradient, then maybe it is being pushed out in the seemingly wrong direction because the particle is going past the local minima/center of the SDF in a single step?

Also, I imagine it's the case that Obi physics is aware of Unity physics, but not vice-versa. So, for example, if an object moves fast enough in a single step that it phases through a stationary taught rope, there is no way for Obi's continuous collision to detect that?