Soft Body Collision - Make Particles Go Away!

[bubbafrye]

Hello,

I am working on a school project that involves a soft-body collision. the SB in question is a flat disk of 'meat' (poly w/ soft body) colliding with a nurbs plate.

I have used 'Make Soft' and have applied a spring. There is a default gravity emitter linked to the 'meat' and I have selected 'Make Collide' with the meat & plate.

so far so good.

When the meat collides with the plate, I get a nice interaction (short bounce & a bit of jiggle).

The Problem:

My disk of meat flattens out to be paper thin - I am not able to get it to return to it's original shape after it is done jiggling.

I figure I either need to somehow kill off the particles, or kill the gravity that is flattening my object.

Any suggestions would be welcome. I will provide more info if nessesary. **it is a requrement of this assignment to use soft body dynamics for the effect.

-Thanks

[failure]

Just setup stiff springs to hold the particles together

[bubbafrye]

Thanks.

I have been using springs, and the stiffer I make them, the more unstable they become. I have been reducing the Dampening to bring it back into check.

After the initial flop (I am dropping it about 8 'inches' above the plate) it looks good, but then it just sort of bubbles and flattens out. If I stiffen the springs any more, it explodes. (current settings : stifned 8, dampening .005)

I have the resilience & friction on the plate set to .5 & .05 respectively.

It seems to me, that there should be a way to kill the particles off after 30 frames or so, and get the meat to return to it's normal shape.

Thanks for any more suggentions.

[failure]

Did you set the springscreation method to "All"?

[bubbafrye]

No, I have been using "Min/Max"

What would be the benifit of using All vs. the other options?

**Just tried 'All' and I am getting the same results - my meat becomes a pancake.

Hmmm... thanks for the suggestions.

I'll up the .mb file of you like (if I can figure out how on this forum).

[bubbafrye]

here's a short render of what is happening..
headcheese.mov

I would reallt like the whole slab of meat to behave stiffer if possible, but If I up the stiffness on the spring any more, it just explodes all over the place.

**as a side note, I am playing back the simulation 'per frame' not 'real-time'.

[joojaa]

Increase steps or use 2 spricng systems (the more simsteps you take the stiffer the springs will become) on top of eachother.

[bubbafrye]

That seemed like a really good idea.

Unfortunately, with 2 spring sets, it just exploded right off the bat. I lowered the dampen to .005 on each, and left them both at a stiffness of 1, and it seemed to have more body, but still deflated by frame 150.

Very frustrating. I have emailed my instructor, but I have not heard back from him yet.

Thanks again for all of your help folks.

Would there be a way to incorporate some sort of goal object in there? I tried "Make copy soft" and placed the original (hard) object on the plate. the finish was nice & jiggly, but the soft object just shot onto the plate in the first frame. Not a very convincing lead-in.

[bkim]

u can keying on goal weight on Softbody. default is .5, so start with this default and increase to 1 ( when your jiggle effect should be done - 1 mean your softbody object will be keep ( or turning back to ) the original shape).

and on your softbody particle attr. there is conserve value (how long particles are effected by field or collide etc..), u can slightly down from default ( it will be 1 then use .8~.95)

best..

sturm

[failure]

Do you preview the simulation with "play every frame" enabled? (just checking)

[bubbafrye]

Yes.

Thanks.

While it does not lok as good as I would like, I was able to get some results by keying the Goal Influence of a duplicate object already placed on the plate. [good suggestion sturm]

I would rather use the Soft option with gravity & collisions though - the results are more organic (until the object deflates that is).

[joojaa]

OK hereas all you need to know of springs. more steps makes EQUALY stiff springs seem stiffer bacese the derivates dont get so high and thus theres more dampening cycles. Also becasue the stesize is higeht it tolerates slightly higer springs NOTE tough its veruy sesnitive at the bigger scales so just adding one 1 too much is too much.

multispring systems if you want to have a fixed step size for other sims you can use 2 or more springs on the same system this acts as if theres 2 steps in one. JUST make sure the original spring sytem is not too high this breaks it nonetheless. 2 then set the second spring to 1/2 the previous one. This is stiffer then one spring about by double because theres 2 successive iterations in the scene. NOW THIS WILL SEEM STIFFER! even tough the values realy realy arent.

You jsut cant pup the values too high only takeing more sim steps helps because there will be a roundoferror at some point.

OKAy a warning DONT ever expect a springed softbpody be a slightly softer rigdbody sim. It wont work the springs leak the energy out of the system.

[dylanmaxwell]

you could satisfy your requirement by applying the softbody to a single surface and then using that to wrap deform the thick steak. the wrap wont flatten your 3d steak because it's only 2d-ish. you won't get any vertical jiggle but it looks like that's not necessary.
-Dylan

[bubbafrye]

I'm interrested in what you are suggesting but not sure if I am fully following you. I do not have any expierience with wrap deformers.

Could you elaborate a little more on them or better yet, point me to a resource/example that explains them a bit?
Thanks for the respnse.

Joojaa,
Thanks for your explinaton as well. I believe I got the jist of what you were saying despite the type-os wink.
One bit of confusion is what you are referring to by 'steps'. I am using the 'Make Soft' option at default settings (not the Duplicate, Make Copy Soft) and I am seeing no opton for 'steps' in either the spring or particle lists in the channel box.

Thanks for all of your comments!

[joojaa]

its s global simulation setting!

Dynamics menuset | Solvers -> Edit Oversampling or Cache Settings...

Wich is why you may want to use 2 spring sytems insetad, because not everything may aneed 2 steps.

[dylanmaxwell]

yeah, If you take a model like your steak and "wrap deform" it to a model like a grid, the steak will bend when you bend the grid. so if you put a non-linear wave or whatever on the grid your downstream steak will receive the deformation.

in this case you'd make the grid your softbody and get that simulating right. Because it starts flat it won't flatten your steak.

www.dylanmaxwell.com/stuff/steak.ma

look at this file if you need
-Dylan

[3dbeing]

My advice, combine every solution that has been offered here, then become a scientist, and test test test, untill you develop a theory, more then likely that's how everyone else developed their solution... great answers everyone, I learned something new too!!