12-08-2021, 07:48 AM
(This post was last modified: 12-08-2021, 01:17 PM by josemendez.)
Hi there,
Both videos you linked to are private, so I need permission to be able to see them.
Rope should be pretty stiff with the default parameters. This being said, the usual mass ratio limitations existing in all iterative solvers (which account for pretty much 100% of all realtime physics engines) also apply to Obi: very heavy objects attached to very light ropes will cause the rope to have spurious elasticity. As a rule of thumb, the mass ratio between objects must not exceed 1:10.
A resolution of 0.5 should be enough for most ropes, and the default amount of substeps (4) should be enough too unless you're dealing with very long ropes and/or very large mass ratios. You could go a bit higher on substeps, but never needed more than 8 in any use case I've ever encountered. That's not enough to cause any performance issues.
(*)This sounds way off. Compliance should be set to zero (its default value) unless you want stretchy ropes, since it's the inverse of stiffness. Any non-zero compliance value will result in elastic ropes, the higher your compliance value, the more slack your rope will have. More compliance = less stiffness.
This might be a shot in the dark, but make sure your solver's constraint relaxation parameters are all set to at least 1. (see: http://obi.virtualmethodstudio.com/manua...olver.html) In the past I've seen cases where the relaxation parameters where set to the minimum value (0.1, which results in constraints only being applied to 10% of their full strength) yielding very elastic ropes regardless of all other parameters.
Both videos you linked to are private, so I need permission to be able to see them.
(11-08-2021, 05:54 PM)greenisfun100 Wrote: My goal is to have the cables be stiff when bearing weight and not let the rest of the bridge sag.
Rope should be pretty stiff with the default parameters. This being said, the usual mass ratio limitations existing in all iterative solvers (which account for pretty much 100% of all realtime physics engines) also apply to Obi: very heavy objects attached to very light ropes will cause the rope to have spurious elasticity. As a rule of thumb, the mass ratio between objects must not exceed 1:10.
(11-08-2021, 05:54 PM)greenisfun100 Wrote: I have tried several things such as manipulating the blueprints resolution, the number of solver steps on the obi solver (to the point of very low fps)
A resolution of 0.5 should be enough for most ropes, and the default amount of substeps (4) should be enough too unless you're dealing with very long ropes and/or very large mass ratios. You could go a bit higher on substeps, but never needed more than 8 in any use case I've ever encountered. That's not enough to cause any performance issues.
(11-08-2021, 05:54 PM)greenisfun100 Wrote: and incorporating a slight reduction in the stretching compliance(*). The last one was the most successful but not quite what I want.
(*)This sounds way off. Compliance should be set to zero (its default value) unless you want stretchy ropes, since it's the inverse of stiffness. Any non-zero compliance value will result in elastic ropes, the higher your compliance value, the more slack your rope will have. More compliance = less stiffness.
This might be a shot in the dark, but make sure your solver's constraint relaxation parameters are all set to at least 1. (see: http://obi.virtualmethodstudio.com/manua...olver.html) In the past I've seen cases where the relaxation parameters where set to the minimum value (0.1, which results in constraints only being applied to 10% of their full strength) yielding very elastic ropes regardless of all other parameters.