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Is there a way to make a rig that keeps my muscle attachments firmly anchored onto two separate (anatomical) bones while the arm bone moves? I want to show a few muscles moving with the shoulder joint but I can't find any similar examples on the internet other than muslce approximations that make flesh bulge. Here I don't need skin.

The goal is to show muscle transfer surgery - how relocating a nearby muscle can bring back movement lost with paralysis after injury. For example, sometimes a portion of the pec major is transferred on top of a paralyzed deltoid muscle. If anyone has any ideas for potential rigging workflows that might allow me to rig an anatomical muscle in this way, please share ideas I might research. I am working with retopologized versions for actual rig tests.

I have been trying to use hook modifiers, but they seem to stop working sometimes.

Thanks! Jimenter image description here

enter image description here

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  • $\begingroup$ Can you post the .blend file? There are several questions tbe pic alone does not answer. Are you using an Armature Modifier? If so, is everything properly weight painted? Are the muscles and bones separate objects? If so, each needs to have the Armature Modifier... and so on, etc. About the "relocating muscle" part of you question, that seems like post-work - editing different renders from scenes with different stages of the procedure together in a single video. $\endgroup$
    – Moshi
    Commented Apr 5, 2018 at 8:45
  • $\begingroup$ I think I have solved the problem of the hook modifier behavior by making custom vertex group hooks. I copied the vert group and assigned it but also made an exact copy as a separate mini-mesh. I will upload the screen shots later today, as I think this workflow is giving the best results I have ever had. You are right, there are really two problems: hook behavior (even with weight painting) and muscle rigging. I think I will treat the rigging with armature as a separate question sometime and take the success of the hook for now. $\endgroup$
    – MedArt
    Commented Apr 5, 2018 at 14:33
  • $\begingroup$ the shiny torus was manipulated with the hook technique I came up with today. If anyone else has trouble with hook behavior, perhaps I should upload the screen shots. $\endgroup$
    – MedArt
    Commented Apr 5, 2018 at 14:38
  • $\begingroup$ FYI the custom vert/hook objects are invisible on the torus but I parented them to the cylinders. I will try on real bones later. $\endgroup$
    – MedArt
    Commented Apr 5, 2018 at 14:41

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enter image description hereI think I have solved the problem of the hook modifier behavior by making custom vertex group hooks. I copied the vert group and assigned it but also made an exact copy as a separate mini-mesh. The shiny torus was manipulated with the hook technique I came up with today. If anyone else has trouble with hook behavior, perhaps I should upload the screen shots.
FYI the custom vert/hook objects are invisible on the torus but I parented them to the cylinders. I will try on real bones later.enter image description here

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Use a spline IK rigging method. Depending on how detailed you need the muscle being moved away from the bone, you can break up each individual muscle into multiple spline IKs. Like if you are just going to move back the whole posterior deltoid from the joint, you can use one curve to represent the whole group. If you only want to peel away part of that muscle, then break the anterior deltoid mesh into multiple meshes, and use the spline on the part that you need to pull away. Great tutorial on how to build a fully animatable rig is at https://www.youtube.com/watch?v=IrXAPC-PLLA. Im working on some anatomical rigging problems too, and built a model with bones, connective tissue, and splines for the muscles. I took a pic here of me detaching one end of the muscle from the bone, using the control empty. If you have more control points on the spline, you could enter image description here peel it away as a nice curve. This green muscle only has 2 control points, so it acts like a point to constraint, with 3 I could bend the muscle into any shape I wantedenter image description here Hope this helps!

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  • $\begingroup$ Thanks Tyler! This looks like a great idea. I imagine that an empty located near the middle of the muscle could also be scaled slightly larger to give the illusion of muscle contraction. I would love to see the final results of your vertebral experiments. $\endgroup$
    – MedArt
    Commented May 5, 2018 at 15:14
  • $\begingroup$ Tyler... have you made progress on the spine rig? $\endgroup$
    – MedArt
    Commented Feb 2, 2019 at 2:20

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