OpenGL, a noob's guide for Android developers

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OpenGL A noob's guide for Android developers Benjamin Monjoie

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The promise https://www.turbosquid.com/3d-models/3d-pine-tree-model/700221

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The reality http://www.script-tutorials.com/demos/145/img1.jpg 300 lines of code later ...

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The challenge

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Roadmap ● What is OpenGL ? ● What about with Android ? ● OpenGL’s internals ● Shaders ● Enter the matrix ● Advices ● Bonus

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Roadmap ● What is OpenGL ? ● What about with Android ? ● OpenGL’s internals ● Shaders ● Enter the matrix ● Advices ● Bonus

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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

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OpenGL & Android ● OpenGL ES 1.0 & 1.1 since Android 1.0 (API 4)

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OpenGL & Android ● OpenGL ES 1.0 & 1.1 since Android 1.0 (API 4) ● OpenGL ES 2.0 since Android 2.2 (API 8)

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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)

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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)

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Graphics driver http://international.download.nvidia.com/webassets/en_US/shared/images/articles/gtx-680m/gtx-680m-chip.png

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Roadmap ● What is OpenGL ? ● What about with Android ? ● OpenGL’s internals ● Shaders ● Enter the matrix ● Advices ● Bonus

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What about with Android ? GLSurfaceView & GLSurfaceView.Renderer onSurfaceCreated (GL10 gl, EGLConfig config) onSurfaceChanged (GL10 gl, int width, int height) onDrawFrame (GL10 gl)

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Roadmap ● What is OpenGL ? ● What about with Android ? ● OpenGL’s internals ● Shaders ● Enter the matrix ● Advices ● Bonus

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OpenGL’s internals https://www.ntu.edu.sg/home/ehchua/programming/opengl/CG_BasicsTheory.html

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Roadmap ● What is OpenGL ? ● What about with Android ? ● OpenGL’s internals ● Shaders ● Enter the matrix ● Advices ● Bonus

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Shaders (GLSL)

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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; }

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Fragment shader - Example precision mediump float; uniform sampler2D uTexture; varying vec2 position; void main() { gl_FragColor = texture2D(uTexture, position); }

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Fragment shader - Example precision mediump float; uniform sampler2D uTexture; varying vec2 position; void main() { gl_FragColor = texture2D(uTexture, position); }

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Fragment shader - Example precision mediump float; uniform sampler2D uTexture; varying vec2 position; void main() { gl_FragColor = texture2D(uTexture, position); }

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Fragment shader - Example precision mediump float; uniform sampler2D uTexture; varying vec2 position; void main() { gl_FragColor = texture2D(uTexture, position); }

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Roadmap ● What is OpenGL ? ● What about with Android ? ● OpenGL’s internals ● Shaders ● Enter the matrix ● Advices ● Bonus

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Enter the matrix https://developer.android.com/guide/topics/graphics/opengl.html#coordinate-mapping

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The strip https://en.wikipedia.org/wiki/Triangle_strip

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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 };

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The strip 0,0 1,0 0,1 1,1 https://pbs.twimg.com/profile_images/616076655547682816/6gMRtQyY.jpg

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The strip 0,0 1,0 0,1 1,1

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Roadmap ● What is OpenGL ? ● What about with Android ? ● OpenGL’s internals ● Shaders ● Enter the matrix ● Advices ● Bonus

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Advices ● Abstract as much as possible

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Advices ● Abstract as much as possible ● Crash often but crash well !

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Advices ● Abstract as much as possible ● Crash often but crash well ! ● Test, a lot !

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Advices ● Abstract as much as possible ● Crash often but crash well ! ● Test, a lot ! ● Use Google’s Play Store’s Alpha & Beta channels

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Roadmap ● What is OpenGL ? ● What about with Android ? ● OpenGL’s internals ● Shaders ● Enter the matrix ● Advices ● Bonus

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https://www.androidleakspodcast.com

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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