MuscleAnalysis set activation override

[mrrezaie]

Hi, users may use MuscleAnalysis in Analyze tool with motion data only, e.g. IK output, to compute muscle quantities such as fiber and tendon lengths. In this case, the tool uses default_activation of muscles (this is not well-documented). So, they must either change it to 1.0 for all muscles or create a dummy (ones) storage file for muscles activation. Here is an example of typical vs default_activation of 1.0:

It would be great if MuscleAnalysis has a property for overriding the activation similar to Plotter. This can be like a check box. Thank you.