Help Update "lag" between cloth and particle attachment target

[josemendez]

Hi Jose,

thanks for the insight!
One last question though: before using Obi cloth, i used the unity cloth implementation.
As unity cloth did not have this problems, I wonder how this correlates to their approach using also some kind of physics...

Cheers,
Christian

Unity cloth is updated in Update(), with a variable timestep (which is completely wrong from a physics standpoint). This results in unstable simulation, random jerks, and fluctuating momentum which causes the cloth to be unable to come to a rest. Basically they're advancing the simulation a random amount of time each frame (will only work acceptably well if you have an exceptionally steady FPS, so that every frame is rendered in the exact same amount of time). Here's a comparison between Unity (white cloth) and Obi (blue cloth):



In addition to this, two-way coupling with rigidbodies is not supported by Unity, probably because it would just blow up due to this unphysical behavior (you can't have objects in the same simulation updated at different frequencies). Don't know what they were thinking when they implemented cloth, tbh  

In Obi you can also force the solver to update in Update() by using a ObiLateUpdater component instead of a ObiFixedUpdater. The associated problems are the exactly same, that's why we strongly recommend using the ObiFixedUpdater (and why it is the default).