Optimizing OpenGL ES Applications

Optimization is an iterative process. It can be time consuming, especially without prior experience determining where bottlenecks tend to occur. Effort should be directed towards the critical areas instead of starting a random place in the rendering code. When the graphics application is complex it may be difficult to know where to start or exactly where optimizations will yield the best return.

Partition the analysis into manageable chunks

Many rendering applications are complex and consist of hundreds of objects. But usually they consist of logically separate rendering code. For example, a rendered image may consist of roads, buildings, landmarks, points of interest, sky, clouds, buildings, water, terrain, icons, and a 2D user interface. It is helpful to write the GL application such that rendering of each type of object can be disabled easily. This allows easy identification of the most expensive objects when benchmarking and therefore makes optimizing the rendering code more manageable.

Become familiar with bottlenecks in the graphics pipeline

It is important to begin optimizations by identifying the performance bottlenecks at the different stages in the graphics pipeline. Because the work introduced in the beginning of the pipeline normally affects the work needed at later stages, it often makes sense to work backwards from the end of the pipeline. An introduction to identifying graphics bottlenecks can be found in the GPU Gems book, "Chapter 28. Graphics Pipeline Performance" (Cem Cebenoyan, NVIDIA).