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FEM blows up, how do I make it stable?


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Hi everyone!

I have been playing around with the FEM material in H13. And I have been looking at making it follow animation. It works fine with a simple torus squashing and stretching but once I try something more complex it blow up after 4 frames or so. Anyone have any idea how to get around this?
Any suggestions would be much appreciated.






I provided an example scene which explodes.


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You can crank up the "Min Substep Rate" to 30+. Even the "Enable Adaptive Substepping" is enabled, when you define this manually, you should get more correct results. If this doesn't help, in the accuracy tab you can set the "Float Precision" to 64.

Edited by schiho
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mine also blows up, but luckily, they blow up when stress is too much and only some, so I can delete them, but in the manual it says "In some simulations, some tetrahedrons or polygons turn huge after a collision. In this case, try increasing the Min Substep Rate until the problem goes away. Sometimes, you can stabilize a problematic simulation without increasing the minimum substepping level much, by increasing the accuracy instead. For example, you could increase the Max Iterations Linear Solve (to say 10000) and decrease the Tolerance Linear Solve (to say 0.0001)." but this didnt help me in my case

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With simulations blowing up in FEM, increasing the min substep rate isn't always the best option.  When you have fem breaking against another object such as a solid object, increasing substeps on the solver isn't enough.  Increasing the global substeps on the Dopnet is the best way to go.  


In my experience if the impact point happens between frames, the FEM object can get caught in the collision geo and blow up.  Another effective way to do this is to up the frame rate to 120fps for the sim and then bring it down to 24.

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