Rigid rope with heavy weight and 2 pin constraints

[dignifiedweb]

Hi,

I was wondering for general advice on how to make the Obi Rope more rigid and less springy? I was able to add more distance constraints (300 or so) and that helped a lot, but I found I also had to take the mass down of each particle (painted to select). I got the rope to be rigid and almost no spring, but my problem is I have a pin constraint on the top particle and a pin constraint on the bottom. The bottom one is attached to a sphere collider and I have to make the sphere rigidbody's weight really light or else the springiness comes into effect in full force again with a heavier weight on it.

Do you think I just have to increase the resolution? I found that resolution (amount of particles) is tough because I'm using a very tiny rope/string.

Any suggestions would be much appreciated, thank you.

[josemendez]

Hi,

I was wondering for general advice on how to make the Obi Rope more rigid and less springy? I was able to add more distance constraints (300 or so) and that helped a lot, but I found I also had to take the mass down of each particle (painted to select). I got the rope to be rigid and almost no spring, but my problem is I have a pin constraint on the top particle and a pin constraint on the bottom. The bottom one is attached to a sphere collider and I have to make the sphere rigidbody's weight really light or else the springiness comes into effect in full force again with a heavier weight on it.

Do you think I just have to increase the resolution? I found that resolution (amount of particles) is tough because I'm using a very tiny rope/string.

Any suggestions would be much appreciated, thank you.

This is a basic issue, common to all realtime physics engines: high mass ratios reduce convergence speed (i.e. make things stretchy and rubber like). Basic rules to avoid stretchiness:

- Use tether constraints when possible. (that is, when at least 1 particle in your rope is fixed). This will ensure the rope does not exceed its rest length under any circumstance. See: http://obi.virtualmethodstudio.com/tutor...aints.html

- If tethers are not applicable in your case, decrease the rope resolution to the minimum acceptable. (less particles=faster convergence). If needed, increase "smoothness" for better mesh rendering at low resolutions. See: http://obi.virtualmethodstudio.com/tutor...eters.html

- Increase distance and pin constraint iteration count in the ObiSolver. This decreases performance, but increases convergence speed (i.e, reduces stretchiness).

- If all else fails, reduce the mass ratio: make the particles heavier, or the attached rigidbodies lighter.

cheers,

[dignifiedweb]

This is a basic issue, common to all realtime physics engines: high mass ratios reduce convergence speed (i.e. make things stretchy and rubber like). Basic rules to avoid stretchiness:

- Use tether constraints when possible. (that is, when at least 1 particle in your rope is fixed). This will ensure the rope does not exceed its rest length under any circumstance. See: http://obi.virtualmethodstudio.com/tutor...aints.html

- If tethers are not applicable in your case, decrease the rope resolution to the minimum acceptable. (less particles=faster convergence). If needed, increase "smoothness" for better mesh rendering at low resolutions. See: http://obi.virtualmethodstudio.com/tutor...eters.html

- Increase distance and pin constraint iteration count in the ObiSolver. This decreases performance, but increases convergence speed (i.e, reduces stretchiness).

- If all else fails, reduce the mass ratio: make the particles heavier, or the attached rigidbodies lighter.

cheers,

Thank you, this helps a lot! I will report back here if I have further details to provide. I am betting the above suggestions will help me, appreciate it!