03-02-2018, 08:47 PM
(This post was last modified: 03-02-2018, 09:02 PM by josemendez.)
(03-02-2018, 08:13 PM)jonworks Wrote: Hello,
Thanks for replying on a Saturday.
Can you tell me what the practical limit is for rope length in this asset? I've taken every suggestion and I'm still not able to get anything that even vaguely resembles how a rope would behave.
About the tether solution you mentioned, "Note that if your rope is long enough it might still "droop"". In this attachment my rope is only 6m long and this is a screen shot of its steady state (after the rope is settled). You can see that the iterations are set to 50. Currently the mass of the attached Rigidbody is 20 and the mass of each rope particle is 20. I was not able to achieve any significant change to this unreasonable amount of droop by changing either the rope mass or Rigidbody mass. I've set iterations all the way up at 500 and it reduces the droop, but still not enough to look even adequate (plus that causes the rope to bounce back and forth forever and never settle).
Rope solutions using the regular physics engine can simulate rope more than 10x this long (60m) and work OK the 90% of the time they aren't crashing the game. What am I doing wrong?
Thanks,
Jon
Hi Jon,
Is it absolutely necessary for your purpose to use such high rope resolution? I think you'd achieve better results by using lower resolution and cranking the rope smoothness up a bit. This would result in less constraints, which would require fewer iterations to appear stiff. See: http://obi.virtualmethodstudio.com/tutor...eters.html
The regular physics engine allows to use capsules as the building blocks for rope. This means they usually use less rigidbodies to create the rope (equivalent to a lower resolution rope in Obi) so they need very few iterations. The downside is that as you might have discovered by now, traditional velocity-based constraint solvers are exceptionally unstable for many applications.
The practical length limit in ObiRope is very much determined by the resolution, your simulation budget and the accuracy you need. Long ropes made of 10 particles and short ropes made of 10 particles are basically the same, as far as the physics solver is concerned. If lowering the resolution is not an option for you, instead of creating just 1 tether you can create one tether per particle, and attach them all to the one that's fixed at the top.