Jump to content

Vellum Inflate From Flattened State?


Atom

Recommended Posts

hmm...curly one, no success from me either....so....really Houdini still can't do simple Balloon pressure. In Max I can simply use negative pressure (not crushing it with a collider) , it works itself into a crumpled heap, then I used positive pressure to blow up the crumpled heap into its original shape (well, a puffy version of it anyway).

Only thing I can think of is have some omni wind blowing from inside the sphere to blow it up...(or fill it with liquid/particles ?)

Edited by Noobini
Link to comment
Share on other sites

well...is that Pressure ? I think that's a 'morph' effect...

So, if you have Atom's collapsed sphere..can you apply internal Pressure to blow it up. As I said in the Max example....it won't get back its ORIGINAL shape....but a puffy version of it.....because there's actual Pressure inside.

While your example, I'm not technical enough to know what the gas solvers are doing...I'm guessing it just a blend/morph effect.

Edited by Noobini
Link to comment
Share on other sites

That video is very interesting. I haven't tried pressure with nonmanifold Geo... No morphs in my setup...I believe the sphere would inflate without that rest blend, I just threw that in to regain the original volume pre-squish, as the restlengths of the squished sphere would produce a smaller object than would be desirable in my opinion... Definitely things to experiment with though

Link to comment
Share on other sites

Thanks for looking into this and the example file. It does look like the effect needs an un-deflated rest state to work. Some others reported this effect could be accomplished by animating the @restlength parameter inside a geometry wrangle, but I have not got that to work yet.

if (s@type=="pressure") @restlength +=1.1;

 

Link to comment
Share on other sites

 

38 minutes ago, Atom said:

Thanks for looking into this and the example file. It does look like the effect needs an un-deflated rest state to work. Some others reported this effect could be accomplished by animating the @restlength parameter inside a geometry wrangle, but I have not got that to work yet.


if (s@type=="pressure") @restlength +=1.1;

 

Here's the hip with animating the restlength in a geometry wrangle

vellum_inflate_odf.hipnc

But you're correct you need some data to know when to stop, otherwise the length will just get bigger and bigger

  • Like 2
Link to comment
Share on other sites

but to me...manipulating restlength......ie, edgelengths is just faking it. While for a balloon material that is rubber, yes agree it physically stretches/shrinks...but let's say it's made of non stretched cloth (or say a paper bag), if you blow air in or suck air out of it, it puffs up or crumples...but edgelengths do NOT change.

The only real proof is I guess if you cut a hole in the geo somewhere...does internal pressure escape and gives you the jet effect ?

Link to comment
Share on other sites

what MAX seems to be doing (along with others, Maya, Marvelous) is simple old school force along N

you can easily implement it in Houdini, and while it's not a true pressure it creates an impression of inflating and even air leaking

not specific to Vellum, you can use this with FEM too and while a tiny wrangle is needed I wouldn't call it jumping through hoops

here is an example similar to boxes above

ts_N_pressure_force.hip

  • Like 5
Link to comment
Share on other sites

agree...I wanted to see what Max was doing so I put a piece of cloth behind the jet stream to see what comes out....even tho the bag moves...there is NO physical airstream rushing out.

I've managed to mock something up in H17, again not true pressure but a fake effect...bit of a hack, upload soon.

Link to comment
Share on other sites

Thanks for all the feedback and solutions. I think the simplest way to handle this is to just record the collapsing geometry and play it backwards. I was hoping to get a little over inflate at the end and then a snap back to original size. But this can do for now.

inflate.gif

Link to comment
Share on other sites

I think it's going to be about blending to the rest position of the un-deflated object, while changing rest length scale and bend stiffness all in the same keyframe...Tie them all together via relative channel expressions.  Not able to test at the moment, but I think that's gonna be the best of all worlds

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...