#### Overview of this book

Animation is one of the most important parts of any game. Modern animation systems work directly with track-driven animation and provide support for advanced techniques such as inverse kinematics (IK), blend trees, and dual quaternion skinning. This book will walk you through everything you need to get an optimized, production-ready animation system up and running, and contains all the code required to build the animation system. You’ll start by learning the basic principles, and then delve into the core topics of animation programming by building a curve-based skinned animation system. You’ll implement different skinning techniques and explore advanced animation topics such as IK, animation blending, dual quaternion skinning, and crowd rendering. The animation system you will build following this book can be easily integrated into your next game development project. The book is intended to be read from start to finish, although each chapter is self-contained and can be read independently as well. By the end of this book, you’ll have implemented a modern animation system and got to grips with optimization concepts and advanced animation techniques.
Table of Contents (17 chapters)
Preface
Chapter 1: Creating a Game Window
Free Chapter
Chapter 2: Implementing Vectors
Chapter 3: Implementing Matrices
Chapter 4: Implementing Quaternions
Chapter 5: Implementing Transforms
Chapter 6: Building an Abstract Renderer
Chapter 7: Exploring the glTF File Format
Chapter 8: Creating Curves, Frames, and Tracks
Chapter 9: Implementing Animation Clips
Chapter 10: Mesh Skinning
Chapter 11: Optimizing the Animation Pipeline
Chapter 12: Blending between Animations
Chapter 13: Implementing Inverse Kinematics
Chapter 14: Using Dual Quaternions for Skinning
Chapter 15: Rendering Instanced Crowds
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# Implementing poses

To store a parent-child hierarchy between transforms, you need to maintain two parallel vectors—one filled with transforms and one filled with integers. The integer array contains the index of the parent transform for each joint. Not all joints have parents; if a joint doesn't have a parent, its parent value is negative.

When thinking about a skeleton or pose, it's easy to think of a hierarchy that has one root node and many nodes that branch off it. In practice, it's not uncommon to have two or three root nodes. Sometimes, file formats store models in a way that the first node of the skeleton is a root node, but there is also a root node that all the skinned meshes are children of. These hierarchies tend to look like this:

Figure 9.2: Multiple root nodes in one file

There are three common poses for an animated character—the current pose, the bind pose, and the rest pose. The rest pose is the default configuration...