Hello,

First of all, I'd like to point out that I've been a Houdini beginner for 18 months.

I'm trying to make a long haircut for an anime character (walk cycle).
For this I use guides that I deform with a "guidedeform" , so far so good.
I use the Vellum Hair, but in the vellum solver I can't go beyond a substep of 1 to have stable guides, beyond that everything starts to shake, and the higher the number of substeps, the more the guides shake and go mad!

For a simple hair test with a little dynamic, I can use a substep of 1 and 1000 constraint iterations, but if I want the character to run his hands through his hair I need a lot more precision and therefore more substeps.

Has anyone come across this problem before?

Many thanks !

Olivier

visualize your pscales to make sure they are not overlapping too much with geo or themselves
and make sure to turn off collisions for root points using i@disableexternal = 1; to avoid them trying to constantly get out of collision with the head

also using Soft Pin constraints with high stiffness is more stable than Hard pin, especially in case of such forced collisions

Many thanks, Tomas, for replying so quickly !

I had already done everything you suggest, but unfortunately the problem persists.
I think the problem lies with the character animation itself, this is my first Houdini rig/skin (I'm far from an expert in this field), and I've certainly made a mistake
When I deform this character with a simple animated lattice, I no longer have the problem of shaky hair...
Nevertheless I still think that no matter how a geometry is deformed (I only keep the @P & @N attributes of this geometry), the Vellum Hair should behave the same way...confusion

-Cheers-

Right, it's also important to make sure your geometry is moving smoothly between frames

So you may need to use TimeBlend SOP to interpolate your geo between frames

You can doublecheck that by turning on fractional frames on timeline and see if your geo moves between frames

Indeed, that's where the problem lies.
I didn't use the animated geometry directly, but through a cache file, and effectively there was no interpolation between the frames.
Using a timeblend SOP solves the problem.

Thanks a bunch for all these clarifications !