OpenGL, a noob's guide for Android developers

Presentation given at Android Makers 2017 in Paris.

OpenGL is often regarded as too complex, obscur or even too low level to be considered when developing an application. Most people will even try to go around it and develop what they want using Views and Canvas to avoid developing with it. Nevertheless, it's not always possible nor the best solution. As someone who have been going through all the learning of OpenGL recently, I have encountered a lot of frustration but also a lot of “aha!“ moment. In this talk, I will try to demystified OpenGL and share the basics of what it is and how to use it in Android to make applications perform better. Also, I will share all the pitfalls and key concepts that you should know when starting with OpenGL.

Transcript

1. OpenGL A noob's guide for Android developers Benjamin Monjoie
2. The promise https://www.turbosquid.com/3d-models/3d-pine-tree-model/700221
3. The reality http://www.script-tutorials.com/demos/145/img1.jpg 300 lines of code later ...
5. The challenge
6. Roadmap • What is OpenGL ? • What about with Android ? • OpenGL’s internals • Shaders • Enter the matrix • Advices • Bonus
7. Roadmap • What is OpenGL ? • What about with Android ? • OpenGL’s internals • Shaders • Enter the matrix • Advices • Bonus
8. What is OpenGL ? http://infos-reportages.com/wp-content/uploads/2016/10/phone_hero-module_hero-image_144 0_2x.png http://fr.ubergizmo.com/wp-content/uploads/2013/02/chromebook-pixel.png http://www.samsung.com/us/explore/family-hub-refrigerator/assets/images/glance/food-manag ement-slide01-mb.png http://www.samsung.com/us/2012-smart-blu-ray-player/img/tv-front.png
9. OpenGL & Android • OpenGL ES 1.0 & 1.1 since Android 1.0 (API 4)
10. OpenGL & Android • OpenGL ES 1.0 & 1.1 since Android 1.0 (API 4) • OpenGL ES 2.0 since Android 2.2 (API 8)
11. OpenGL & Android • OpenGL ES 1.0 & 1.1 since Android 1.0 (API 4) • OpenGL ES 2.0 since Android 2.2 (API 8) • OpenGL ES 3.0 since Android 4.3 (API 18) (almost)
12. OpenGL & Android • OpenGL ES 1.0 & 1.1 since Android 1.0 (API 4) • OpenGL ES 2.0 since Android 2.2 (API 8) • OpenGL ES 3.0 since Android 4.3 (API 18) (almost) • OpenGL ES 3.1 since Android 5.0 (API 21)
13. OpenGL & Android • OpenGL ES 1.0 & 1.1 since Android 1.0 (API 4) • OpenGL ES 2.0 since Android 2.2 (API 8) • OpenGL ES 3.0 since Android 4.3 (API 18) (almost) • OpenGL ES 3.1 since Android 5.0 (API 21)
14. Graphics driver http://international.download.nvidia.com/webassets/en_US/shared/images/articles/gtx-680m/gtx-680m-chip.png
15. Roadmap • What is OpenGL ? • What about with Android ? • OpenGL’s internals • Shaders • Enter the matrix • Advices • Bonus
16. What about with Android ? GLSurfaceView & GLSurfaceView.Renderer onSurfaceCreated (GL10 gl, EGLConfig config) onSurfaceChanged (GL10 gl, int width, int height) onDrawFrame (GL10 gl)
17. Roadmap • What is OpenGL ? • What about with Android ? • OpenGL’s internals • Shaders • Enter the matrix • Advices • Bonus
18. OpenGL’s internals https://www.ntu.edu.sg/home/ehchua/programming/opengl/CG_BasicsTheory.html
19. Roadmap • What is OpenGL ? • What about with Android ? • OpenGL’s internals • Shaders • Enter the matrix • Advices • Bonus
20. Shaders (GLSL)
21. Vertex shader - Example precision mediump float; uniform mat4 uMVPMatrix; attribute vec4 vPosition; attribute vec4 vTextureCoordinate; varying vec2 position; void main() { gl_Position = uMVPMatrix * vPosition; position = vTextureCoordinate.xy; }
22. Vertex shader - Example precision mediump float; uniform mat4 uMVPMatrix; attribute vec4 vPosition; attribute vec4 vTextureCoordinate; varying vec2 position; void main() { gl_Position = uMVPMatrix * vPosition; position = vTextureCoordinate.xy; }
23. Vertex shader - Example precision mediump float; uniform mat4 uMVPMatrix; attribute vec4 vPosition; attribute vec4 vTextureCoordinate; varying vec2 position; void main() { gl_Position = uMVPMatrix * vPosition; position = vTextureCoordinate.xy; }
24. Vertex shader - Example precision mediump float; uniform mat4 uMVPMatrix; attribute vec4 vPosition; attribute vec4 vTextureCoordinate; varying vec2 position; void main() { gl_Position = uMVPMatrix * vPosition; position = vTextureCoordinate.xy; }
25. Vertex shader - Example precision mediump float; uniform mat4 uMVPMatrix; attribute vec4 vPosition; attribute vec4 vTextureCoordinate; varying vec2 position; void main() { gl_Position = uMVPMatrix * vPosition; position = vTextureCoordinate.xy; }
26. Fragment shader - Example precision mediump float; uniform sampler2D uTexture; varying vec2 position; void main() { gl_FragColor = texture2D(uTexture, position); }
27. Fragment shader - Example precision mediump float; uniform sampler2D uTexture; varying vec2 position; void main() { gl_FragColor = texture2D(uTexture, position); }
28. Fragment shader - Example precision mediump float; uniform sampler2D uTexture; varying vec2 position; void main() { gl_FragColor = texture2D(uTexture, position); }
29. Fragment shader - Example precision mediump float; uniform sampler2D uTexture; varying vec2 position; void main() { gl_FragColor = texture2D(uTexture, position); }
30. Roadmap • What is OpenGL ? • What about with Android ? • OpenGL’s internals • Shaders • Enter the matrix • Advices • Bonus
31. Enter the matrix https://developer.android.com/guide/topics/graphics/opengl.html#coordinate-mapping
32. The strip https://en.wikipedia.org/wiki/Triangle_strip
33. The strip POSITION_MATRIX = { -1,-1, 1, // X1,Y1,Z1 1,-1, 1, // X2,Y2,Z2 -1, 1, 1, // X3,Y3,Z3 1, 1, 1, // X4,Y4,Z4 }; TEXTURE_COORDS[] = { 0, 1, // X1,Y1 1, 1, // X2,Y2 0, 0, // X3,Y3 1, 0, // X4,Y4 };
34. The strip 0,0 1,0 0,1 1,1 https://pbs.twimg.com/profile_images/616076655547682816/6gMRtQyY.jpg
35. The strip 0,0 1,0 0,1 1,1
36. Roadmap • What is OpenGL ? • What about with Android ? • OpenGL’s internals • Shaders • Enter the matrix • Advices • Bonus
37. Advices • Abstract as much as possible
38. Advices • Abstract as much as possible • Crash often but crash well !
39. Advices • Abstract as much as possible • Crash often but crash well ! • Test, a lot !
40. Advices • Abstract as much as possible • Crash often but crash well ! • Test, a lot ! • Use Google’s Play Store’s Alpha & Beta channels
41. Roadmap • What is OpenGL ? • What about with Android ? • OpenGL’s internals • Shaders • Enter the matrix • Advices • Bonus
42. https://www.androidleakspodcast.com
43. OpenGL A noob's guide for Android developers https://plus.google.com/+BenjaminMonjoieXzan https://medium.com/@Xzan https://twitter.com/Xzan https://twitter.com/android_leaks https://medium.com/@xzan/opengl-le-guide-du-noob-pour-développeur-android