SONOFPAT'S C.G.

The Sonofpat's "Skinbones" joint setup tutorial

#1 Shoulders

I discovered a simple, but very effective way of making joints in animatiion master without smart skin or weights. Since a picture paints a thousand words, the flash movies below gives an idea of the final results.

So what are good joints made of in AM? The answer is simple - skin, bones and "skinbones". Let's start with the skin as seen in the image below.

THE SKIN:

The most important part is the shoulder ring as shown. In general, I tried to keep the splines as simple as possible for animation while providing details needed for the upper arm.

THE BONES:

The bones as seen in the image below are the biceps and shoulder bones which function as levers in the traditional sence of bones.

Note the lowered position of the biceps. This allows the arm to pivot in a more natural position when it is at the side.

THE 'SKINBONES':

These are intermediate bones that are children of the shoulder bones and are oriented in such a way that the CPs they are connected to mimic the skin at the joint as the limb rotates in different positions. When the biceps are at the side, those at the top rotate more, when the arm is extended outward, those at the back rotate more etc.

THE 'SKINBONES': Top View

Here's a top view. Note the forward position of the biceps. This allows the arm to pivot in a more natural position when it is extended forward.

A bird's eye view of the shoulder ring and the skinbones that control it are shown for clarity.

The bones were laid out in the radial position when modeling but their final position were tweaked by openning the pose window shown below together with the model window in the bones mode.The arm was moved in different positions and the length and position of each bone tinkered with in the model window untill the best shape of the joint was obtianed.

THE SETUP:

The skin bones each have an orient-like constraint to the biceps with enforcement varying from 50% at the very top and back to 15% below the armpit in the back and front. The position of the root of each of these bones were tweeked to get the desired movement of the mesh. That's all for now. If I can find the time I will probably write a proper tutorial

Hope you can make sense of all of this if not drop me a line