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[Christian Jakob <question230986@xxxxxxxxxxxxxxxxxxxxx>]

Question #230986 on Yade changed:
https://answers.launchpad.net/yade/+question/230986

    Status: Open => Answered

Christian Jakob proposed the following answer:
I do not really understand, why you want to compute inertia "in each step" ...
Inertia of a body is constant since mass (or shape) does not change. So it is calculated once after creating or modifiing a clump*. There is no need to calculate it in each step.

Inertia tensor is actually just approximated in Yade [1]. It is simply
the sum of all inertia tensors of clump members. If you need a more
exactly inertia tensor, you can try to improve the section between line
121 [2] and 124. For this you can have a look how you can get inertia
tensor by integration [3].  I just found a german entry in wiki (no
english, sorry) about inertia tensor.

Feel free if you want to improve this section.

Regards,

Christian

[1] https://github.com/yade/trunk/blob/master/core/Clump.cpp#L138
[2] https://github.com/yade/trunk/blob/master/core/Clump.cpp#L121
[3] http://de.wikipedia.org/wiki/Tr%C3%A4gheitstensor

*Clump::updateProperties is called by following methods:
- clump()
- appendClumped()
- replaceByClumps()
- addToClump()
- releaseFromClump()
- adaptClumpMasses()

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