Help Tether for ropes and rods?

[JhonatasFarias]

Hi there, in an old tutorial of obi rope making a pendulum it shows a component of tether constraints, as you can see at min 7:



Inside the version I have (6.0.1) there is no component like this, how can I achieve tether constraints like that in ropes and rods?

[josemendez]

Hi there,

Tethers are no longer needed for ropes, increasing the amount of substeps gives much better (more physically accurate) results. After all tethers are just a "hack" to minimize stretching, but they introduce artifacts in many cases, specially when the rope is not a simple straight line.

You can find an in-depth explanation of how the simulation works and the effect substeps/iterations have on it here:
http://obi.virtualmethodstudio.com/tutor...gence.html

[Giantbean]

Hi there,

Tethers are no longer needed for ropes, increasing the amount of substeps gives much better (more physically accurate) results. After all tethers are just a "hack" to minimize stretching, but they introduce artifacts in many cases, specially when the rope is not a simple straight line.

You can find an in-depth explanation of how the simulation works and the effect substeps/iterations have on it here:
http://obi.virtualmethodstudio.com/tutor...gence.html

The page you refer to still has tether constraints and even if I put sub steps at 500 the rope stretches' to the ground rather then making a pendulum in 6.2? I have tried setting the weight of the rope to 1 and .1 as well as setting the attached objects to 1 and .1 and I am attaching the rope between two objects with Obi Particle Attachment on start and end nodes (two on each end to hold the rope without unwanted rotation) This worked in older Obi versions but I'm struggling to get it to work in 6.2 where its supposedly easier. Are there any new videos for how this is properly done in the new version?

[josemendez]

The page you refer to still has tether constraints

Hi!

Remember that the manual is structured in two parts: the introduction/constraints (which is common to all Obi assets) and then individual sections for each specific asset. That page I'm referring to is common to all Obi assets (cloth, ropes, softbodies and fluid), tethers are present since they're used in cloth as explained there:

Tether constraints: These constraints are used to reduce stretching of cloth.

and even if I put sub steps at 500 the rope stretches' to the ground rather then making a pendulum in 6.2?

Just make sure you're using dynamic attachments. Static attachments (the default) are one-way only, which means the rope will blindly follow the rigid-body it is attached to without applying forces back to it. See:
http://obi.virtualmethodstudio.com/manua...ments.html

This thread on making a good pendulum might be helpful:
http://obi.virtualmethodstudio.com/forum...t=pendulum

[Giantbean]

...
Just make sure you're using dynamic attachments. Static attachments (the default) are one-way only, which means the rope will blindly follow the rigid-body it is attached to without applying forces back to it. See:
http://obi.virtualmethodstudio.com/manua...ments.html

This thread on making a good pendulum might be helpful:
http://obi.virtualmethodstudio.com/forum...t=pendulum

Thanks I had looked at each of those but re-reading them was helpful. I found that the Obi Rigidbody was coming in with "Kinematic For Particles".  When I turned that off it started working.

[josemendez]

Thanks I had looked at each of those but re-reading them was helpful. I found that the Obi Rigidbody was coming in with "Kinematic For Particles".  When I turned that off it started working.

Yep, kinematic rigidbodies have infinite mass. By default that checkbox is disabled, so it should have been enabled by error (or copied from another scene). Glad you found the issue!

Let me know if I can be of any help