chain break to pieces

[ali]

Just get "dynamic chain" example from XSI 7 and try to recreate it in Houdini. But chain is always break to pieces. I try to tune different parameters from RBD solver but problem is still here. In maya and XSI this scene simulate correctly with default solver parameters. So what magic parameter can help me to resolve this problem?

chains1.zip

[mangi]

hi there try this :

RBD , Collision TAb

Use Volume Based Collision. un check this

This will keep the chain from breaking like you say.

the collada import you have made has some nodes that give errors , maybe it should be made in a claener fasion.

mangi

chains1fix.hipnc

[ali]

>Use Volume Based Collision. un check this

now simulation became slow. very slow.

And this is not collada's bug. I recreate geo in houdini but nothing changed.

chains1_new.hipnc

Edited August 19, 2008 by ali

[ragupasta]

Sorry I cant download attachments at work, but I got this working using volume based collisions, and its super fast. Hope this helps

If you look at this file I have done 2 different methods. The first is a way bringing the links merged in as a single RBD and its very linear and hard in movement. Then there is a switchDOP in there and I have brought all the links in as seperateDOP obj and merged them together using mutual relationship inside a mergeDOP. There is probably a lot better ways to do this, but Im not a pro I do this for fun

ChainSwing1.hipnc

ChainNewSorenson.mov

[ali]

Yes. This is fast and didn't break because in your example is only 5 chains and isn't have a ball on the end of chain. Please, download my last example and try it (22 chains).

Edited August 20, 2008 by ali

[mangi]

still testing ,

This is in regards to the poster of the original issue. I see that in xsi the sim in this case has a pre example of the chain and ball.

In houdini you have to set this up yourself. I did make my own scene because I preffered to do this. Just to see how to make it.

I was wonder why you are using Laser Scan for the collission ?

Not to sure if something has been changed in the 9.5 version , Laser scan is really fast , but I don't think it is used for an object like a donnut.

well atleast that what I learned from the DVD gnomon dynamic tutorials, version 8 of houdini

The Laser passes from one end to the other?

be back soon, cheers

mangi

I am worrking on getting a bit of preformace running windows 64bit. problems to make quicktime , excuse me

the chain.rar is a tif sequence that you can load in the flipbook .

cheers mangi

chain.avi

chain.rar

[ali]

ok. thanks. But what about time of this simulation?

I looked at this example in XSI 7 and was very impressed. This scene was simulated in realtime!! Maybe this is dirty calculations, but chain isn't break and animation looks realistic.

[old school]

SoftImage uses ODE for it's dynamics:

http://www.ode.org/

As you described it is very fast but accuracy is an issue as primitives are used to describe the objects.

The open source agreement allows Avid-Softimage (and others) to use this solver as long as any changes to the code are added to the site.

There is a basic implementation of the ODE solver that runs in DOPs:

http://forums.odforce.net/index.php?showforum=40

http://odforce.net/wiki/index.php/ODESolverDOP

It isn't a first class solver in that it can't interact with other solvers nor does it use the forces at this time.

[digitallysane]

On the XSI mailing list some time ago:

that really is a shame.

It's true, I hope they will extend the collision shapes in the next realeases!

Seems the ICE-Simulate Rigid Bodies only works on some kind of convex hull/bounding box of the obstacle. Is this true?

So much for "speed". Calling that dynamics next to DOPs is like calling OpenGL a renderer next to Mantra or PRman. Technically it's true, and its a hundreds times faster. But which one you'll use for production?

Dragos

[mangi]

Thank's old school,

For this clarification.

very wise

mangi

[ali]

Thanks.

I recreate this example using wire and constraints. But when I add box for collisions test I see that only wire is collide with it. The ball is not collide.

So were is mistake?

chainball.zip

[curveU]

Thanks.

I recreate this example using wire and constraints. But when I add box for collisions test I see that only wire is collide with it. The ball is not collide.

So were is mistake?

hi ali, I also want to know the reason of this problem. Have you found out the answer for this?

Thanks,