FleX spring system and particle mass

Hi all,

I’m working with FleX 1.1.0 trying to optimize a specific set of spring systems. I am working within the CLI that Benjamin Felbrich developed (https://github.com/HeinzBenjamin/FlexCLI), so it is a bit of a nontraditional setup, but thus far it has gone quite well.

Onto my question:
Based on my testing it seems that particle mass does not effect spring systems. For any mass above 0, there is no change to the behavior of the spring system. The result of this is most apparent when applying to meshes of differing densities. Particularly in cases with extremely high density meshes, there just isn’t a way to create high tension systems.

Am I missing something here or is this the correct behavior?

Thanks,
Oliver

Yes, this is expected with the PBD constraint model. Basically only the ‘relative’ mass between the two particles matters.

This is a limitation that stiffness in PBD does not generally correspond to physical concept of stiffness. We addressed this in a follow up method called XPBD, but it is not yet integrated with Flex.

Generally to achieve high-stiffness you need to modify substeps/iterations, as you noticed modifying mass itself won’t help for this.

Cheers,
Miles

We addressed this in a follow up method called XPBD, but it is not yet integrated with Flex.

Is this something that is being worked on? XPBD seems like a great step to make things more stable and accurate.