Getting started with open gl es 2
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  • http://www.khronos.org/registry/gles/specs/2.0/es_cm_spec_2.0.24.pdf

Transcript

  • 1. So Cal Code Camp Summer ’12 Getting Started With OpenGL ES 2.0 By Matt Galaviz
  • 2. 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
  • 3. 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.
  • 4. 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
  • 5. 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!
  • 6. 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
  • 7. 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
  • 8. 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)
  • 9. Sample Shaders Vertex Fragment
  • 10. Shader Creation• Create Program• Create Vertex and Fragment shaders• Attach Vertex and Fragment shaders• Compile• Hope for the best!
  • 11. Shader Creation Example Taken from iOS
  • 12. Shader Usage• Use Program• Enable VBO’s – Pass Data • Attributes • Uniforms – Draw Objects – Repeat data/drawing as needed• Disable VBO’s
  • 13. Shader Usage Example Taken from android
  • 14. OpenGL ES 2.0 Availability• Android: 2.2• iOS: 3.0• WebGL: 1.0• Others
  • 15. 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
  • 16. 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
  • 17. Poll• Do you currently use OpenGL ES?• Another graphics API?• What platform do you use?• Are you planning to support multiple platforms?• Preferred platform?
  • 18. My Resources/References• Delicious: http://www.delicious.com/mattgalaviz• Github:• http://www.github.com/geminileft
  • 19. 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
  • 20. The End• Questions/Comments• Contact me @ matthew.galaviz@gmail.com