Help Grab the middle of a rope?

[josemendez]

I'm working on a Vive VR project that will have a loop at the top with a rope threaded through it and each side dangling down.  The user will be able to grab any point along the rope with the motion controllers and pull.  With standard joint ropes, this tends to cause all sorts of physics problems, especially if the user pulls too far too quickly or twists the joints around.

I saw the videos of Obi Rope, and it looks like you can easily move the ends of the rope around without a problem, but would something like this be possible - allowing the rope to be grabbed at different points along its length with virtual hands and pulled around?  And if so, could you maybe point me in the right direction of how to go about it?

Thanks!

Hi there!

There's no difference in grabbing the ends or any other point in the rope. Ropes are basically chains of particles, you can freeze any particle you wish along the rope and move it around. This is done by setting the inverse mass of the particle to zero, and setting its position to whatever you want. See:

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

Keep in mind that absolutely no solver will be able to handle arbitrarily large forces applied to a body, specially not if collisions are involved. You should clamp the maximum force an user is able to exert when pulling on the rope no matter what solver you use (Obi, PhysX, or any other). This is just a limitation of realtime physics: large and sudden forces need higher computation time to be handled with enough precision, so there will always be a threshold that once surpassed, breaks the simulation. Obi is no exception to this.