What is the correct way to rig a shoulder?

There are MANY videos showcasing working shoulder rigs, but not a single video explaining HOW to do it and it’s infuriating.

Shoulder movement is one of the most common movements you do when doing animations yet there is no documentation on it whatsoever.

I need to be able to rotate the shoulder like this:


What resources are there? Any videos? Anything at all!?

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Hi, i don’t really have an answer for you but i was wandering how did you made this excellent reference.

Maybe this will help you…

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Generally follow muscular anatomy of the area in question, as well as the bones they connect to. The only bone that’s very mobile around this area is the scapula, which you might want to take into account if you’re serious about making a nice realistic shoulder.

Particularly relevant muscles are : the pectoral muscle which connects the sternum to the humerus, the trapezius which connects the spine to the scapula, the deltoid which connects the scapula to the humerus. Modeling those as b-bones going in the direction of the muscle fibers works pretty well in my experience.

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I am mostly going about having cartoon characters or game characters where precision does not matter. This means I would have a bone for torso and then a bone for the arm.

         | ------------- arm
         |
         |
       torso

However in this case I would go about like this:

   clavicle
  |~~~ -------------- arm
  |   :
  |  : scapula
  |
  torso

As then going about to move the arm, cause the clavicle and scapula to move as well (based on constraints), and then considering that those two bones have their own weight paints as well, they would cause more natural and proper deformations.

Then probably it would also quite an important step about having extra mesh blend deformations, so the results are better fine tuned.
(Having blend shapes helps as well).

Though I think that the best deal, would be to let Blender get a proper muscle system, that would allow us to get proper deformations, in relation to muscle bending. This way far better accuracy (without tricks and hacks) could be achieved.

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This is the best answer yet- it’s a documented, realistic, functional method for rigging shoulders in tutorial format that can be easily followed

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Well… Organic Rigging is a complicated subject.

What you’re handling, that Shoulder Joint, is what I call a ‘Complex Joint’.
Another well-known example, would be the Pelvis (Hips-Thigh) Joint.

In the case of the Complex Joint of the Shoulder:
One one hand, the humerus, Upper Arm Bone, has got a wild scope of Rotation on all directions (such Rotations, affecting the Angle between 2 (or more) Deform Bones sharing Blended Weights together, are dangerous, because of how the ‘stone age’ Skinning algorithms work in CG software like Blender; massive generated Artifacts will be generated spontaneously, due to such higher Rotations).
On the other hand, Complex Joints have plenty of ‘Anatomical Asymmetries’. It’s not like Rigging a Finger Joint, a Knee Joint or an Elbow Joint, not even a Neck; it’s much, much harder to get the Deforms look organic and natural, in the case of Complex Joints.

Usually, at least one Corrective method is required, in order to solve such Rigs.

You could simple go for the conventional approach: the Corrective Shape Keys method.
Or your could go for some Corrective Armature Deform method, from which derives several Rig Setups; but there isn’t a “correct” way to do that. Or rather, “correct” would be subjective discussion, because if you ask more experienced riggers, while some will think that 1,000 Helper Bones with labyrinthic interactions and with Auto-Weights only (no Weight Painting required!) is a great solution, some others will think that using just a few economic Helper Bones is good enough and more cost-efficient (even though Weight Painting would be required). Personally, I give credit to all plausible solutions; but I usually am more inclined to look forward the most uncomplicated, versatile and cost-efficient solutions that work well enough for whatever is Stylized in Character Design or does not require hyper-detailed anatomical shapes. On that approach’s regard, there is the Fan Bone(s) technique, or the ‘Smoother Bone’ technique’ (basically, a Bendy Bone Spline/Set, that is used to Smooth the Mesh Join Deforms).

Above all the previous methods, in terms of preventing Artifacts to be generated in the first place, is the non-orthodox approach, that relies on changing the Rest Position of the Upper Arm (Bone and Mesh, but essentially it’s about the Mesh). People tell about T-Pose, A-Pose… but for a ‘smarter’ Shoulders Rig, it would be something like a ‘Y-Pose’; where the Arms would be stretched upwards diagonally (could still be on the plane of the Torso though). Unfortunately (at least I know from the context of Blender), the problem of this method, is that, although it rigorously reduces generated Artifacts according to the different, chosen Rest Position, it will make the whole project less ‘regular’, not only in terms of… what we expect to be working on directly (Modelling/Sculpting) for Model Sheets in the creative process of 3D Characters or if we need to make adjustments to the 3D Character’s Mesh during Rigging, but, moreover, by having a Rest Position that is way less regular (T-Pose is very regular in that sense), making and maintaining the Rigging Mechanisms (like Bone Orientations and Positioning, for FK, IK, etc.) can become much more complicated to solve.
Unfortunately, there can only be 1 Rest Position at a time for the same 3D Character; hence, so, there is no way that I know to cheese the system. The Weight Painting operating with the conventional Skinning algorithm in use, will always respond directly to that single, current Rest Position of the Mesh. Shape Keys do not count as additional, secondary Rest Positions for that matter; if they could, then we could Rig anything organic single-handed; since we could determine, for each Deform Bone in the Rig (in principle, corresponding to a respective Weight Painted Mesh portion of the Model), which Rest Position(s) to use (or even to ‘Interpolate’ from in the case of a Mix of 2 or more Rest Positions), in order to set the Deforms into working.

Here are some samples which I find interesting, for Shoulders Rig in Blender

This is more for the mechanism; but, having a more sophisticated mechanism (Control/Mechanism Rig) at hands, is often better for, later on, developing the Deform Rig (which might involve Corrective methods).

Here is an interesting example of Corrective Armature Deform method only approach, but that uses relatively intrincated amount of Helper Bones, but relies on Auto-Weights only:

This clip I’ve made some time ago is a proof of concept, that a combination of 2 Corrective Armature Deform methods: the (Oriental) Fan Bone + the ‘Smoother’ Bone technique (a simple Bendy Bone Spline; Blender Studio riggers apparently use that a lot on their Sprite Fright short feature film 3D Character Rigs), can indeed work well together. Unfortunately, this sample is just a Simple Joint (Elbow), and not a Complex (Shoulder). But, the same techniques, if applied to Complex Joint, if they cannot solve everything, they still can help.

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Every single time i had looked into some biomedical research of the locomotion system and the animations was done by scientiest they looked fake and the best natural looking movements i saw was done by artists fakeing the real thing.

Think about it… maybe that’s the reason why there is no documentation

It’s an art.

And if someone mastered it over some years… he doesn’t simply tell you how it is made any doesn’t get a dime for it… :stuck_out_tongue_winking_eye:

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