Vellum substep issue.

[Butachan]

Hi everyone,

I am sharing this simplified version of a project of mine cause I have an issue that is really baffling me.

It's a hair simmulation, just one hair which I am manipulating its pscale through SOP solvers to create some worm like movement,

It works completely fine as long as I keep the system with 1 substep, but if I increase the number of substeps it goes ballistic!

I have other solvers that really polish the movement of the worm they all work fine, as long as I don't increase the number of substep to more than one. Is like the SOP solver multiplies its effect per substep.

I have no idea what could be causing this, worse I don't understand the why and that really bugs me.

Any help would be really appreciated.

Best,

Nicolas.

Edit: I believe its the internal collision being multiplied, or calculated in each substep in the SOP solver,  but no so such how to address this yet.

Edit 2 : to clarify when the behaviour is acceptable.

VellumSubstep.hiplc

Edited March 6, 2019 by Butachan

[Midasssilver]

Bump

Edited March 7, 2019 by Midasssilver
Was not able to resolve

[cudarsjanis]

bump

[KarlRichter]

Increasing the pscale without changing the constraint length is what is causing this sim to behave strangely. When the pscale is increased, it is making the sim fight against the constraint length and creates interpenetrations. At low substeps, the behaviour is not as noticable, but is still there (run the sim with the gravity off to see what I mean). This could be solved in a number of ways:

- Turn off self collision.

- Use another sop to run over the constraint geo and increase the length along with the pscale.

- Turn down the stiffness of the stretch constraint.