Soft body parts sometimes disappear on collision

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What steps will reproduce the problem?
1. Load two soft bodies from attached .node and .ele files
2. Generate 64 clusters for both of them
3. Place them one above another and let fall down
4. When they collide some features of both soft bodies disappear

What is the expected output? What do you see instead?
Expected behavior is this:
http://youtu.be/Ki8YcJDk7vU
No soft body parts disappear. This can be reproduced on default cube model from 
demos.

On my model I see this:
http://youtu.be/9VY_wiyX1ms
Some parts disappear on collide.

What version of the product are you using? On what operating system?
I reproduced it on trunk revision 2644. My OS is Windows 7.

Please provide any additional information below.
Reproducing depends on inverted mass of nodes (larger values cause better 
effect), on model topology (with default cube model I can't reproduce it), on 
clusters count (more clusters cause better effect) and maybe other factors.

Just in case I attach modified demo files
In SoftDemo.cpp I changed Init_TetraCube method to generate my test case
In SoftBodyHelpers I added a method to load tetgen data from file.

There is a related forum thread:
http://www.bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=9304

Original issue reported on code.google.com by eagle...@gmail.com on 19 Aug 2013 at 9:14

Attachments:

• cube.1.ele.txt
• cube.1.node.txt
• btSoftBodyHelpers.h
• btSoftBodyHelpers.cpp
• SoftDemo.cpp

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Softbody clusters have some known issues indeed. Hopefully someone can fix it, 
with your reproduction case.
Thanks!

Original comment by erwin.coumans on 21 Aug 2013 at 11:10

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moved to https://github.com/bulletphysics/bullet3/issues/86

Original comment by erwin.coumans on 30 Mar 2014 at 5:59

• Changed state: Done