Hello team,

I am trying muscle setup on Houdini 20. Looks like if I paint out the muscle end constraint, all the other constraints do not work anymore. The muscle geos just fall down. I have to use the muscle end, right? Its a must, not an option?

Best,
Chen

You don't have to use the MuscleEnd constraint. In fact, there's a toggle on the MuscleSolver that allows you to bypass it altogether if you needed to do that.

If you do paint it out or disable MuscleEnds, then you need to make sure the MuscleToBone constraint is set up properly. That will be the only constraint remaining that will hold muscles and bones together.

If you turn on the MuscleToBone visualizer on the MuscleSolverVellum>Guides, do you see any constraint vectors? If not, does the muscle attribute: @muscletobonemask contain non-zero values? In the MuscleConstraintProperties node you should see a heatmap/mask for muscletobone.

Hi John,

Thanks for your reply.

Yeah, I have the MuscleToBone constraint and disable MuscleEnds. But it still does not work.

from that snapshot, it looks like your MusclePaint node is upstream from the MuscleConstraintProperties node.
So what I assume is happening is:

• MusclePaint is not painting values in the muscletobonemask attribute. It's getting initialized to 0.0.
  
• MuscleConstraintProperties is detecting an existing muscletobonemask attribute and not overwriting it out of an abundance of caution.
  

The result is a zero-weighted muscle-to-bone constraint.

You should either move the MusclePaint node downstream, and thereby let the MuscleConstraintProp node do the initializing, or, enable the MuscleConstraintProp>Mask Falloff toggle to force it to overwrite the muscletobonemask attribute via the parameters.

Thanks, All good now.