3D modeling is an extremely complicated process that takes many years to master. Drawing well in 2D is difficult enough, but the thought process behind creating characters that work in full three dimensional form is another whole level of skill altogether.
Ribeye is built by the modeler based on hand-drawn animation model sheets done by Mike. It's hard enough 'sculpting' an accurate 3D version of a 2D character like Ribeye- just getting him to look right on the 'outside' is only half the task!
Beneath the outward appearance of the character, is an inner structure that's incredibly complicated. There are actually 'bones' that control the character's limbs and motion. Beyond that, there are controls that the animator uses to manipulate the character's features, allowing him to talk, blink his eyes, and make facial expressions. All of these inner workings operate based on a given range of computer-coded control that is set up by a skilled 3D modeler.
Creating this internal structure called 'rigging' is an extremely difficult skill to master; it requires a lot of very precise calculation, and knowledge of how to create anatomy that simulates the actual laws of physics. For example- in reality a person cannot twist their leg 180 degrees backward, nor have their arm disappear inside their torso. A 3D model by contrast, can easily break any rule of physics if not given a set of programmed restraints that mimic the real world. Unrestrained, the contortions a character goes through when moved look ridiculous on screen.
When an animator poses the character -like a digital puppet- the inner anatomy as 'rigged' by a good modeler, makes the character move and behave in a way that gives the illusion of true volume, weight and gravity.
It's a fascinating process! I had to the good fortune last year to work on a 3D animated feature film, using the application 3D Max. It was an experience that's hooked me on wanting to do more 3D animation.