• Virtual is an option for SetConstraints that causes a Jacobian matrix based on virtual displacements to be generated, rather than a Jacobian based on an Euler transformation.
• Setting Virtual->False causes SolveMech to run more slowly, but SetConstraints builds the model equations more quickly.
• Virtual has no effect unless the current solution method is Angular.
• The default setting is Virtual->True.
• See also: Euler.
Load the Modeler3D package and define a simple model.
First the model is rebuilt with global angular coordinates so that the setting of the Virtual option will have some effect. We use the size of the Jacobian, in bytes, as a crude measure of the cost of evaluating it.
Now the constraints are rebuilt with Virtual->False. The size of the resulting expressions has almost doubled.