Efficient Morph Target Animation Using OpenGL ES 3.0

Abstract

Demand for impressive graphics in mobile apps has given rise to ever-more powerful GPUs and new graphics APIs such as OpenGL ES 3.0. These advances enable programmers to write cleaner and more efficient implementations of computer graphics algorithms than ever before. One particular area that stands to benefit is the facial animation of characters in mobile games, a technique that is commonly implemented using morph targets. Morph target animation requires artists to pre-create multiple poses of a model offline. Later on, during application execution, these poses are mixed together in varying quantities to create animation sequences such as blinking eyes or a frowning face. When used in conjunction with skinning, the technique can serve as the foundation of a feature-rich character animation system. Historically, morph target animation has seen heavy use in PC and console games but a lack of flexibility in earlier graphics APIs has led to complicated or expensive implementations on mobile platforms. This chapter describes an efficient implementation of morph target animation that makes use of the transform-feedback API introduced in OpenGL ES 3.0. The application in this chapter is a continuation of the Gremlin demo, which was first introduced in a previous article [Senior 09]. The demo has been entirely rewritten and has been updated to take advantage of OpenGL ES 3.0 on PowerVR Series6 mobile GPUs.