|11 November 2012||#1|
Join Date: Oct 2012
Shoulder rigging question
The youtube link is a shoulder rigging demonstartion someone has made and posted.
I think you can easily surmise that I am interested in this video because shoulder rigging is diifcult to me, lol; I very much admire the clean action and deformtion of this person's rigging, and would like to implement similar concepts (I am a novice at rigging myself, and only understand the basics.)
So if anyone could help me interpret what this rig is doing, I would be grateful!
1) do you guys think that this rig is employing shape keys (why, why not)
2) What are the cyan and yellow clusters of bones around the biceps, and what might they be doing?
3) why is the clavicle divided into two bones?
4) what are the bones parented to the spine that are around the outer ribs doing?
5) what constraint or technique do they employ to get the bones to align with that red icon?
6)why are the deformations so clean? when I have built similar rigs, I get pinching on the top of the shoulder, and big bulges under the arms under similar extensions.
If anyone could answer some of these questions, or perhaps interpret what is going on here best as they may, I would be grateful!
I would also be helpful if anyone could point out materials which focus on the problems of the shoulder and clavicle in blender!
Last edited by joeraynor : 11 November 2012 at 02:08 AM.
|11 November 2012||#2|
Join Date: May 2004
Shoulders are tough regardless of the package used. This solution in the video looks pretty solid, but without wireframes, it's difficult to gauge the integrability.
1) I don't think it's using corrective shapes, the sheer number of joints makes it look like it showcasing skinning
2) The Cyan/Yellow joints look like helper joints to deform specific areas of the arm. As they seem to ride along with the primary joints. A similar setup can be found here:
3) Not sure why the clavicle would have 2 joints, prehaps a twist fall off or left over from a cartoony setup option
4) The bones around the chest (in the back) are mimicing the motion of a scapula/deltoid. Since the others aren't moving, it may be to help with the initial skin weights so the arm doesnt influence the chest or vice versa.
5) By red icon, do you mean the manipulator? Not sure, looks like an IK system moved out further than the length of the joints.
6) To get better definition in the shoulder and limbs in general, you can use more helper joints. For example, if you had a helper joint located where the bicep would be that scaled in relation to the elbow joint bending. Another big thing to look into is twisting. Here's a good tutorial:
One a side note: try not to get frustrated about deformations. You can get really far with base binds, and correct as needed for the shot/production. Trying to come up with a 100% all the time solution isn't practical. So approach it piece by piece and try not to over complicate it. Make sure you have good joint placement, then that you are painting weight well, then find out where its falling apart and fix that.
Hope this helps.
|11 November 2012||#3|
Character Technical Director
Join Date: Apr 2002
Check out this page it will give you some help maybe.
The rig has two joints on for the shoulder and one for the arm. This is a modo type set up with a rotation deformer and a sculpt for each direction.
|11 November 2012||#4|
Join Date: Feb 2006
You say you are a beginning rigger? Well, Shoulder rigging is advanced, so don't feel too frustrated.
Essentially, you have two choices: One, build a complex joint structure that covers the many ways a shoulder can move and/or deform or two, build a simple rig and fix the bad defomrations using corrective morphs. The two previous answers essentially gave you references for both paths.
If you are interested in Hippydrome's approach, here is a thread on BlenderArtist that shows the idea of using shapekeys in Blender to correct the bad deformations:
Hippydrome's Approach In Blender
“Every child is an artist. The problem is how to remain an artist once we grow up.” - Picasso
|11 November 2012||#5|
Join Date: May 2004
Hi joe ,
It always was my favorite subject in character deformation.
nowadays i tend to use lot of twist joints, helper joint and corrective shape database.( For this I use custom python plugin nodes or specialized c++ deformer ).
One way to reach your goal is to have a solid workflow to define key pose and blend the shapes nicely.
The second point that works for me is to embed a predefined twist in my corrective shape:
the overall twist in a limb is achieve by a separate/additive deformation layer.( it can save you time as you need less shapes in this setup )
For simple ball articulation i use roughly 16 shapes but ints important to note that only 4 key pose is important: the other one are interpolation pose created from them.
For the hip region i try to support a huge range of motion so i have double the number of pose( 30 ) to be able to have smooth interpolation even though lots of them are impossible to reach in real life( but as animation is about exaggeration / simplification / amplification its not illogical to do so ).
The shoulder needs to support 2 articulation( the shoulder blade translation/aim target and the humerus rotation ) and thus needed between 70/140 shapes to work ( at least on my last attempt), which is impractical, and can drive mad any rigger .
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