Houdini Pop Grain issue

[gao]

  Hello everyone. Recently I saw <Meshing Grains> tutorial .But i have issue in this tutorial . So I want stop popgrain of constraints bounce when i want to break constraint. As you know I don't want constraint looks like spring.I try to use pop drag. It 's doesn't work. I check in OD(Link)  .someone say use rest length property ,but i can't start it. so Could you give some sTips or hip file? Thank you very much.

[Zybrand]

Hi Terry,

Do you have an example of what you are trying to make?

Yeah the focus of that tutorial was about meshing. The nature of those constraints means that as soon as they can they will snap back to their @restlength distance. You can update the restlength as they stretch but you will have to store an extra initial rest length attribute to compare against. Also updating the restlength will affect strain which is tested for breaking constraints so if it rest length grows you constraints might not break. So you might have to setup a custom constraint breaking setup or trick the solver some other way.

I hacky way to slow the snapping back to rest down is using acceleration limit and a speed limit and a bit of velocity blending.

If you have access to vellum I think you have a better chance of controlling that motion if you move your setup over there as there are more controls you can use than with grains. Have a look at the hip file attached setting a high damping ratio help slowing the constraint down after they break.

hope that helps.

zj_vellum_grain_damping_ratio.hiplc