Object with mass but no inertia

[Giovanni Mottola]

Dear all,
I'm trying to model a body as a point-mass, discarding the rotational degrees-of-freedom.
I would like to set a positive mass with a zero inertia, but I don't know how.
Here's what I tried:

end_e->SetMass(1.0f);            // set dynamic properties
end_e->SetInertiaXX(ChVector<>(0.0f, 0.0f, 0.0f));

This however doesn't work: the simulation starts correctly but the body doesn't appear in the Irrlicht application.
A workaround would be to set an artificially low inertia. Is there any other way to do this?

Best regards,
Giovanni Mottola

[Alessandro Tasora]

hi Giovanni,

you cannot discard the rotational DOFs by using zero inertia, somewhere in Chrono guts this will end in division by zero.

Actually, if you want to discard rotational DOFs (ex particles that does not roll) the process should be opposite, setting very high (->infinite) inertia - although some solvers such as Barzilai-Borwein or APGD might have troubles also in such case.

Otherwise, avoid the ChBody object: in fact there is an object with no rotational DOFs: it is the ChFEANodeXYZ that is used also for tetrahedral meshes. It cannot have a collision or visualization shape assigned to it, though.

Alessandro

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[Giovanni Mottola]

Dear professor,

thanks for the advice. Since I need to have at least a visualization shape, I will keep using the ChBody, but setting artificially high inertia values.

Best regards,

Giovanni