Performance issues

[josemendez]

Regarding tense ropes etc: i disagree, you can achieve tense ropes using articulated physics. I can see how there would be issues in a particle simulated rope, but i thought you'd get better results than this. Even though it is physically impossible to make a rope 100% straight between points, you can still minimize the amount of sag. An alternative (and most likely better) solution for this in my case would be to script each particle to pull towards the spline with a certain weight (when a nearby plug is disconnected, the particles become released). So firstly, what is your formula for evaluating the position of each particle on the spline? Or would it be even better to just save an array with the particle positions at start and use that? 


Thank you very much for the tip with handles, this is what i was looking for. I will try it out and see how it works, hopefully the crashes won't persist.

Hi there,

I mentioned that you should switch to a different kind of solver for completely tense ropes, one of them is ABA: Articulated Body Algorithm (Featherstone's). However it has several drawbacks that limit its use:

- Impulse application is O(n) in the amount of bodies in the multibody (instead of O(1)). This can quickly degrade performance in relatively simple cases, and reduce the amount of "links" useable. A 100-bodies long chain sitting on the floor would require ten thousand impulse evaluations per frame, which is highly unpractical.

- Does not support loops of any kind, only acyclic hierarchies are supported.

In your case, you should really use tether constraints (also known as LRAs or long-range attachments). They basically allow you to achieve zero stretch in ropes that have at least 1 particle fixed/handled. They work by directly connecting each free particle to the 4 closest fixed/handled particles. This will make sure that they do not get too far away from the plugs, thus preventing any stretch. Using them in conjunction with handles should allow you to achieve perfectly tense and stable ropes. See:

http://obi.virtualmethodstudio.com/tutor...aints.html