Game Engine Architecture

554 11. Animation Systems

from the modifi ed local pose. Obviously, a post-processing operation

that does not require global pose information can be done between stag-

es 2 and 3, thus avoiding the need for global pose recalculation.

6. Matrix palett e generation. Once the fi nal global pose has been generated,
   each joint’s global pose matrix is multiplied by the corresponding in-
   verse bind pose matrix. The output of this stage is a palett e of skinning
   matrices suitable for input to the rendering engine.
   A typical animation pipeline is depicted in Figure 11.44.

11.10.1. Data Structures

Every animation pipeline is architected diff erently, but most operate in terms

of data structures that are similar to the ones described in this section.

11.10.1.1. Shared Resource Data

As with all game engine systems, a strong distinction must be made between

shared resource data and per-instance state information. Each individual character

or object in the game has its own per-instance data structures, but characters

or objects of the same type typically share a single set of resource data. This

shared data typically includes the following:

• Skeleton. The skeleton describes the joint hierarchy and its bind pose.


• Skinned meshes. One or more meshes can be skinned to a single skeleton.
  Each vertex within a skinned mesh contains the indices of one or more

Outputs

Inputs

Decompression

and

Pose Extraction

Blend

Specification

Pose

Blending

Skinning

Matrix

Calc.

Global

Pose Calc.

Local Pose

Rendering

Engine

Matrix

Palette

ProcessingPost -

Skeleton

Clip(s)

Local

Clock(s)

Global

Pose

Game Play

Systems

Figure 11.44. A typical animation pipeline.