Hi everybody,
I'm actually working on a pretty simple Vellum sim as it may seem,
but I'm actually facing a wall and I can't find any help online.
I'm trying to replicate a zipper effect with constraints between two Vellum Cloth, I wanna relax a constraint when the zipper goes one way and strenghten it when it goes the other.
I'm using the “stretchstiffness” attribute to drive the constraints but I can't find a way to animate it.
I have a parameter that allow me to vary the stretchstiffness attribute along the zipper seam and so I tried to animate it,
but the constraint remains the same.

Here is my scene

I didn't have a chance to verify this, but I have something for you to try. On the Vellum Constraints, the stretch stiffness has a scaling attribute that lets you inherit that attribute into the sim if it exists on the geometry. Make an attribute called f@stretchstiffness and change the scaling to by attribute. Then make sure your attribute is animated before going into the sim. See if that properly inherits the animation of your stretch stiffness.

Yeah that's waht i did in the scene I animate the @stretchstiffness attribute value on different points going from 0 to 1 and then i aplly and mult to it. Even tho the value is animated before the solver, it looks like it doesnt update the value.
I wounder if we need a SOP solver inside the Vellum solver in order to get it

I see, that looks like it is the case. Made a quick test scene and got the same result. If you have issues getting a sop solver inside the vellum solver setup, then perhaps using vellum nodes inside of a dopnet, and having a solver dop in there, might make things a little easier to set up. It makes sense, because attributes are inherited into the sim with the vellum solver on the first frame of the sim (such as thickness, which we can only visualize on the first frame). Using a solver inside a DOP is probably a good workaround.