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+--- Thread: Help delete fluid bouncing (/thread-2825.html)
delete fluid bouncing - JskT01 - 23-03-2021
The fluid that I designed is in a container which I move from left to right and up to down, when moving it up to down it tends to bounce and I want to avoid this since it is not realistic for my simulation, I already played with several parameters but they have not worked for me
Imagen blue print
RE: delete fluid bouncing - josemendez - 23-03-2021
(23-03-2021, 07:45 PM)JskT01 Wrote: The fluid that I designed is in a container which I move from left to right and up to down, when moving it up to down it tends to bounce and I want to avoid this since it is not realistic for my simulation, I already played with several parameters but they have not worked for me
Imagen blue print
Hi!
There’s no explicit “bouncing” implemented in Obi, the collision model has no restitution parameter. There’s only two possible sources of bouncing: compressibility, or depenetration.
If the fluid is too compressible, it will compress when you move the container up, then decompress when you stop (giving it in a bouncy look). You need to use more substeps. (In the ObiFixedUpdater)
If the fluid gains velocity because it starts frames inside of a collider and has to be taken out, you can reduce the max depenetration velocity (in the ObiSolver).
A video of the issue would help, as I can’t really tell for sure what you’re referring to. Cheers!
RE: delete fluid bouncing - JskT01 - 23-03-2021
(23-03-2021, 08:45 PM)josemendez Wrote: Hi!
There’s no explicit “bouncing” implemented in Obi, the collision model has no restitution parameter. There’s only two possible sources of bouncing: compressibility, or depenetration.
If the fluid is too compressible, it will compress when you move the container up, then decompress when you stop (giving it in a bouncy look). You need to use more substeps. (In the ObiFixedUpdater)
If the fluid gains velocity because it starts frames inside of a collider and has to be taken out, you can reduce the max depenetration velocity (in the ObiSolver).
A video of the issue would help, as I can’t really tell for sure what you’re referring to. Cheers!
I have the parameter max depenetration at 0, I attach a video Video Bouncy , thank you , I hope you can help me
RE: delete fluid bouncing - josemendez - 24-03-2021
Hi, just saw your video about bouncy fluid.
That's just due to the fluid's compressibility. The fluid compresses when you move the bucket up, then in de-compresses (bounces) once the movement stops.
Keep in mind that all fluids are compressible to some degree, and that this is a simulation, so it cannot be made completely incompressible. The strength of XPBD (the simulation method used by Obi) is precisely that remaining error in the simulation manifests itself as compliance (compressibility, in the case of fluids) instead of an unstable simulation.
To reduce compressibility, you can use more substeps and/or iterations. However this will make the simulation more expensive, so be careful. This manual page goes into details about how the simulation works and how iterations/substeps affect it: http://obi.virtualmethodstudio.com/tutorials/convergence.html
Quote:An insufficiently high iteration count will almost always manifest as some sort of unwanted softness/stretchiness, depending on which constraints could not be fully satisfied: Bouncy, compressible fluid if density constraints could not be met.