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[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

> shearForce = (phys.ks*dt+phys.cs)*shearVelocity;
>
> but should not be:
>
> shearForce += (phys.ks*dt+phys.cs)*shearVelocity;

Both wrong I think... If spring and dashpot are in parallel it should be 
something like :

elasticShearF += shearVel*phys.ks*dt;//check plasticity condition on 
that one ...
viscousShearF = shearVel*phys.cs;
shearForce = elasticShearF + viscousShearF;//... or that one, depends on 
your constitutive model

The solid (elastic) force can accumulate with increments, the viscous 
one is uniquely defined as a function of current velocity (no history).

> Moreover once we rotate the force we have:
>
> shearForce -= shearForce.Cross(axis);
Still the same, the rigid body rotation is not impacted by the 
constitutive equations.

Bruno