Softbody collision problem

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brainjuice
Posts: 7
Joined: Mon Aug 24, 2009 11:09 am

Softbody collision problem

Post by brainjuice »

We're working on a serious simulation. It involves interaction between soft tissue and rigid immovable bodies... e.g a device pressing into living tissue.

The problems we are having is that collision between the softbodies and the rigid collision shapes (bullet primitives like spheres and boxes) are very inaccurate.

One thing we discussed is that the scale of our world is small... about 1 unit across which means our collision shapes are of the order 0.01 to 0.1 units in dimension. The coder we've had working on this says this is comparable to the default collision tolerences in bullet which would explain the lack of accuracy. We've not been able to establish if we can lower that tolerence relative to our world's size, or if there are numerical limits beyond which things will start to fall apart?

Edited: We are on our way solving this, but now we need further adjustments, see here post requesting PAID work: http://bulletphysics.com/Bullet/phpBB3/ ... f=9&t=4000
Last edited by brainjuice on Wed Aug 26, 2009 11:31 am, edited 1 time in total.
bone
Posts: 231
Joined: Tue Feb 20, 2007 4:56 pm

Re: Softbody collision problem

Post by bone »

Anytime I see "serious simulation", I'd probably recommend using double precision by defining BT_USE_DOUBLE_PRECISION. I don't know of any engineering or scientific simulation that uses single precision.

I suspect the tolerances are still an issue, but I don't have much experience with that so I'm not sure. I understand that making them smaller can possibly make collision less stable, so you have to be careful.
brainjuice
Posts: 7
Joined: Mon Aug 24, 2009 11:09 am

Re: Softbody collision problem

Post by brainjuice »

thank you.

do you know anybody in this forum --or anywhere else, that has specific expertise in soft bodies? We are truly in need to solve this.

b
bone
Posts: 231
Joined: Tue Feb 20, 2007 4:56 pm

Re: Softbody collision problem

Post by bone »

No, I don't, but I'd recommend you search the following sub-forum for softbody users:

Bullet Physics SDK Discussion, Feedback and Bug Reports:
http://www.bulletphysics.com/Bullet/php ... um.php?f=9
brainjuice
Posts: 7
Joined: Mon Aug 24, 2009 11:09 am

Re: Softbody collision problem

Post by brainjuice »

will do that, thank you!
brainjuice
Posts: 7
Joined: Mon Aug 24, 2009 11:09 am

Re: Softbody collision problem

Post by brainjuice »

Edited: We are on our way solving this, but now we need further adjustments, see here post requesting PAID work: http://bulletphysics.com/Bullet/phpBB3/ ... f=9&t=4000
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