So Cal Code Camp Summer ’12 Getting Started With OpenGL ES 2.0 By Matt Galaviz
About Me…• Currently part-time DBA (SQL Server)• Deep interest in game development• Started with Core Animation• Moved to OpenGL ES 1.1• Meetup conversation inspired/challenged to learn OpenGL ES 2.0• Never wanted to be a Graphics Programmer ;)• Currently on 2nd or 3rd version of graphics/game engine, iOS and android
History• OpenGL Website: http://www.opengl.org• Introduced in 1992• 2D/3D graphics API• Available on many different platforms• Windows, Unix, Linux, OS X, etc.
History Continued• OpenGL ES Website: http://www.khronos.org/opengles/• OpenGL ES 1.1 similar to OpenGL 1.5• 1.1 = Fixed Function Pipeline• OpenGL ES 2.0 released circa 2008• 2.0 = Programmable Pipeline
Programmable means more…• Control – do what you want with shaders• Responsibility – shaders need data and programming• Complexity – shader source, compilation, VBO’s, MVP matrices, etc.• Discipline – maintaining shader data, switching shaders and other things can cause code to run SLOWER. Best practice adherence is a must!
Differences between 1.1 and 2.0• Model/View/Projection (MVP) – 1.1: Can call built in functions (glMatrixMode, glIdentity, glPushMatrix, glPopMatrix, etc.) Taken from android
MVP Differences Continued– 2.0: Pass MVP matrices to shaders • Side note: Matrix libraries may not be available on all platforms and may vary in use Taken from android
Shaders• The programmable piece• Write in GLSL ES, similar functionality of C• Vertex Shader: handles vertex data• Fragment Shader: handles pixel data• Comprised of attributes, uniforms and varying with types and variable precision• See specification for more details (approx. 200 pages)
Getting Started• Identify goals – Support ES 1.1 and 2.0 • Rewrite code to support provider/consumer model • Provider submits only primatives to consumer • Consumer determines how to handle primatives • Consumer = ES 1.1 or 2.0
Getting Started Continued– Multi Platform • Many differences between android/iOS • Java more similar to C++ in style and look than Objective-C • NDK on android possibly even more similar – Adds another layer of complexity • Even same platform can vary – iOS 5 GLKit • Keep shader source as separate files • Structure classes as similar as possible
Poll• Do you currently use OpenGL ES?• Another graphics API?• What platform do you use?• Are you planning to support multiple platforms?• Preferred platform?
My Resources/References• Delicious: http://www.delicious.com/mattgalaviz• Github:• http://www.github.com/geminileft
Other Resources/References• OpenGL ES 2.0 Specification http://www.khronos.org/registry/gles/specs/2 .0/es_cm_spec_2.0.24.pdf• GLSL ES Specification http://www.khronos.org/registry/gles/specs/2 .0/GLSL_ES_Specification_1.0.17.pdf• PowerVR developers http://www.imgtec.com/powervr/insider/pow ervr-insider.asp
The End• Questions/Comments• Contact me @ firstname.lastname@example.org
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