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sir i am using upper extremity arm model for cmc simulation of human arm, as it already has one joint r_z for ration of body wrt z axis . The model works fine with it . but as soon as i add other rotation and translation to model(r_x,r_y,t_x,t_y,t_z). the simulation fails and gives error like SimTK Exception thrown at MuscleFixedWidthPennationModel.cpp:219: or (fiber length >0) condition not met. there is no motion in all these six solid body translation and rotation . even if i lock all these translation and rotation is still get ame error

The error indicates that one of the muscle fiber lengths is reaching zero. It's difficult to diagnose the issue without seeing the model. To troubleshoot, you could try plotting the fiber lengths to narrow down which muscle is causing the issue, then check the properties of this muscle (e.g., how the GeometryPath has been defined).