hi, houdini newbie here!

i’m having trouble with vellum constraint stitch points (i’ll call them velcon).

i’m setting up a cloth sim with buttons around the neck. the cloth sim works fine, but when i try to attach the buttons using velcon stitch point, they fall off during simulation. i’m using velcon cloth + velcon struts for the button setup, and combining them with the cloth using velcon stitch. i painted two attributes for the stitch: one to define stitch points on the buttons, and one to mark the target area on the cloth.

the stitches show up when visualized, and scrubbing the timeline looks fine. but when i run the vellum solver, the buttons start “melting” or breaking away. i’ve tried increasing substeps (up to 5) and constraint iterations (up to 500), but no luck. i also tried replacing stitch with pin to target and that worked but it broke the button shape.

i followed a tutorial where this setup worked fine, so i’m not sure what i’m missing. any ideas or help would be super appreciated. thanks!

Hi I'm encountering the exact same problem, did you find a way to fix this?

unfortunately, i can't fix the problem but i would suggest try to increase the substeps

I wouldn't use the buttons in the simulation itself, rather deform them to the cloth afterwards. If you're in H21 or later, then you can use Surface Deform to deform the buttons, and turn on the Blur toggle and crank the Blurring Iterations and Step Size to maximum to preserve the shape. If you're in an earlier version of Houdini, or if the Surface Deform doesn't preserve the shape rigidly enough, you can use Guide Deform with the Geometry to Deform set to "Arbitrary Geometry" and then toggle on "Rigidly Transform Pieces".