Chapter 39: Understanding Rigging and Working with Bones

What does a graveyard have in common with animated characters? The answer is bones. Bones are used as an underlying structure attached to a character that is to be animated. By using a bones structure, you can produce complex character motions by simply animating the bones and not having to move all the vertices associated with a high-resolution character.

Although Max includes a prebuilt skeleton with its Biped system, at times you may want to build a custom bones system because not all characters stand on two feet. Have you ever seen a sci-fi movie in which the alien was less than human-like? If your character can't be created by modifying a biped, then you need to use the traditional manual methods of rigging.

This chapter focuses on the process of manually rigging a character, which, depending on the complexity of your character, could end up being even easier than working with bipeds. It also gives you a clear idea of concepts of rigging.

Creating a Rigging Workflow

A rigged character starts with a linked hierarchy. A linked hierarchy attaches, or links, one object to another and makes it possible to transform the attached object by moving the one to which it is linked. The arm is a classic example of a linked hierarchy: When the shoulder rotates, so do the elbow, wrist, and fingers. Establishing linked hierarchies can make moving, positioning, and animating many objects easy.

A bones system is a unique case of a linked hierarchy that has a specific structure. You can create a structure of bones from an existing hierarchy, or you can create a bones system and attach objects to it. A key advantage of a bones system is that you can use IK Solvers to manipulate and animate the structure. Another advantage of a bones structure is that you can constrain the motion of bones so the motion is forced to be realistic, just a real character.

CROSS-REF 

IK Solvers are covered in Chapter 40, "Adding Inverse Kinematics."

After the bone structure is created, it needs to be edited to fit the skin mesh that it will control. You also need to define the limits of each bone and joint. This helps prevent the skeleton from moving in unrealistic ways. Applying IK systems is another way to control the motion of the bones and joints. This process of creating a skeleton structure and defining its limits is called rigging.

After you've edited a system of bones, you can cover the bones with objects that have the Skin modifier applied. This modifier lets the covering object move and bend with the bones structure underneath. The process of attaching a model to a bones system is called skinning.

CROSS-REF 

The Skin modifier is covered along with other aspects of skinning a character in Chapter 41, "Skinning Characters."

After a character is rigged and skinned, the character is ready to be animated.