Building the Perfect Armpit

Works in progress and technical screen shots.

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Building the Perfect Armpit

Postby brkurt » Tue Apr 22, 2014 4:05 pm

Hello everyone...this is the result of a month of intensive study and work; I'll create a tutorial for it when the animation is finished.

As you all know, a new rig is being created for Alpha 1.1. I have been working in parallel on the same problem and have discovered the same truths about working with Blender and Makehuman.
The most difficult area to rig is the armpit, because four muscle (vertex) groups and one arm bone have to move in 3 axes, and more critically, must rotate in 3 axes.

This creates twisting meshes that are nearly impossible to resolve, if one wants to create realistic clothing that both drapes and folds. Blender's Cloth Modifier does an excellent job of draping, but is essentially useless for folds. This means the solution must take several steps. What I am presenting here should work for the MakeClothes plugin.

The first step is to create clothing at the armpit by using a 16-vertex circle. This amount of vertices gives the right size of polygons for draping the figure. Next, once your garment is created, the four vertex groups: deltoid, clavicle, scapula and armpit must traverse the arm joint all the way to the trapezius muscle.


After this crucial step, everything gets a lot easier, because most of the hard work is done by posing the rig. I am going to use the most difficult pose called Contact Left from the my walk cycle to illustrate the point. One of the secrets to removing twists in the mesh--either body or garment--is to rotate the vertebrae, one vertabrae at a time. For my rig, those bones are Lumbar One, Lumber Two, Thorax One, and Thorax Two.


With only minor adjustments to the deltoid and humerus bones, you can get this result:


and on the right. Note how easy it will be to create the Shape Keys necessary for real-world folds now.


You can try the model yourself:

Note that these problems were resolved using the Alpha 5.1 mesh; it is much easier with MH 1.0! :D
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