Vellum pressure point attribute anim issue

[RT_SD]

Hi. I'm running into a Vellum issue when animating the pressure contraint inside the Vellum SOP solver.

I've got a growing mask attribute on the geo to drive the pressure using point() in the vellum constraint properties in the solver, and another to drive stretch of the cloth. The stretch restscale animates gradually with the mask as expected, but the pressure does nothing until a certain frame then inflates all at once.

I've set up a simple scene to show the problem. It should be inflating where its red from the start but seems to happen instantly at frame 25 only. Can't figure out why. I've compared my setup to similar ones on YT and nothing is jumping out at me.

 

Pressure problem.hiplc

[RT_SD]

OK, think I've figued it out partially at least, the pressure contraint is a single polyline... it can't be animated locally by a point attribute, its all or nothing. Which makes sense, as the pressure will equalise everywhere inside if you blow up a balloon.

 

So I have to animate pressure globally on the object, and only control the local expansion with the stretch stiffness, is that right?

[abxx]

On 7/5/2024 at 7:10 AM, RT_SD said:

OK, think I've figued it out partially at least, the pressure contraint is a single polyline... it can't be animated locally by a point attribute, its all or nothing. Which makes sense, as the pressure will equalise everywhere inside if you blow up a balloon.

 

So I have to animate pressure globally on the object, and only control the local expansion with the stretch stiffness, is that right?

 hey, i also want to make a object inflate with attribute. is there solution you figure it out?

 

[RT_SD]

On 8/15/2024 at 6:19 AM, abxx said:

 hey, i also want to make a object inflate with attribute. is there solution you figure it out?

 

Yes, you don't try and animate the pressure attrib since its global, you create localised effects with the stretch and bend stiffness atribs instead.

[rlc4love]

On 7/5/2024 at 9:10 PM, RT_SD said:

OK, think I've figued it out partially at least, the pressure contraint is a single polyline... it can't be animated locally by a point attribute, its all or nothing. Which makes sense, as the pressure will equalise everywhere inside if you blow up a balloon.

 

So I have to animate pressure globally on the object, and only control the local expansion with the stretch stiffness, is that right?

This article is absolutely fantastic!