Vellum bubbles of different sizes

[jeanmarc]

Hi folks,

I am quite beginner with vellum and for a shot i am trying to create bubbles of different sizes and simulate them in Vellum, but i cant figure out how to make them keep their volume during the sequence.

I use points and animated pscale to emit but as soon as they are emitted (with the good size) they all resize to a fixed amount.

Thanks for your help

Jmvellum_bubblesNotKeepDifferentSizes_01.hip

[Atom]

I think I would call that bug. The Vellum solver isn't applying the pscale attribute to the constraint instances, which it should. After birth, they reliably conform the mesh to the original source.

The fix is fairly simple. Just supply a random scale every frame to the source sphere. This will insure the constraints are scaled before being submitted to the solver.

Place this in the Scale field of the move_up transform node.

fit01(rand(@Frame),0.5,3.8)

Make sure to set your pscale to 1.0 in the wrangle, or the initial size will be undone.

Edited December 17, 2021 by Atom

[jeanmarc]

Thank you Atom!

Exactly what i was looking for, I cant believe its a bug! i spent so many time tweacking vellum constraints and all that stuff.

 

 

[ryew]

Out of curiosity, I tried adding a Vellum Rest Blend DOP after the Vellum Source DOP.  Setting the Vellum Rest Blend DOP Update Frequency parameter to "Each Frame" seems to help except when the spheres birth in overlapping positions and become jumbled together.