Lecture 8 - OpenGL on Android
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OpenGL ES
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Cut down version of OpenGL
Fixed point support
Found in many mobile platforms (Android, iOS,
Blackberry, Symbian, 3DS, etc.)
Designed for slower GPUs and CPUs
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Version 1.x
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OpenGL ES 1.0 based on OpenGL 1.3 and OpenGL ES 1.1
based on OpenGL 1.5
Common and Common-Lite (only fixed point) profile
Fixed-function rendering pipeline
Reduced features: no quad and polygon primitives, no
stippling, only multisample AA, reduced drawing modes,
no display lists, etc.
OpenGL ES 1.1 adds better multitexture support, VBOs,
clip planes, mipmap generation
Android 1.0 and higher
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Version 2.0
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Based on OpenGL 2.0, but reduced fixed-function pipeline
support
Not compatible with OpenGL ES 1.x
OpenGL ES Shading Language
ESSL only has forward branches and fixed iteration loops
Transforming and Lighting functions replaced by shaders
Better performance than OpenGL ES 1.x in many cases
Android 2.2 and higher
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Version 3.0
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Compatible with OpenGL ES 2.0 and OpenGL 4.3
Standardized texture compression
Better texturing support
New Shading Language version with full support for
integer and floating point
Improved flow control
Easier portability
Android 4.3 and higher
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GL Surface
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Manages a surface (a region of memory which can be
displayed on screen)
Manages an EGL display (an OpenGL rendering context)
Dedicated rendering thread
Can provide debug information
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EGL
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Virtual display which contains a rendering context
2D and 3D rendering
Allows having multiple smaller surfaces on the actual
screen or drawing to offscreen buffer
Used by SurfaceFlinger and other compositors (Wayland,
Mir) or libraries (SDL)
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Demo
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Create GL2JNIView and set it as a view for the activity
Constructor initializes the view
private void init(boolean translucent, int depth, int stencil) {
setEGLContextFactory(new ContextFactory());
setEGLConfigChooser( translucent ?
new ConfigChooser(8, 8, 8, 8,
depth, stencil) :
new ConfigChooser(5, 6, 5, 0,
depth, stencil) );
setRenderer(new Renderer());
}
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Demo
public EGLConfig chooseConfig(EGL10 egl, EGLDisplay display) {
/* Get the number of minimally
matching EGL configurations */
int[] num_config = new int[1];
egl.eglChooseConfig(display, s_configAttribs2, null,
0, num_config);
int numConfigs = num_config[0];
/* Allocate then read the array of minimally
matching EGL configs */
EGLConfig[] configs = new EGLConfig[numConfigs];
egl.eglChooseConfig(display, s_configAttribs2, configs,
numConfigs, num_config);
/* Now return the "best" one
(matches rgba specifications) */
return chooseConfig(egl, display, configs);
}
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Demo
private static class Renderer implements GLSurfaceView.Renderer {
public void onDrawFrame(GL10 gl) {
GL2JNILib.step();
}
public void onSurfaceChanged(GL10 gl, int width, int height) {
GL2JNILib.init(width, height);
}
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
// Do nothing.
}
}
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Demo
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setupGraphics
 Compiles vertex and pixel shaders into a program
 Defines Uniforms, Attributes, etc.
 Sets initial camera position and viewport
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Demo
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renderFrame
 Updates camera
 Sets shader program
 Sets Uniforms and Attributes for current frame
 Draws triangles
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Android Tools for Debugging and Profiling
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Logging
Debugging Developer Options: Overdraw, Clipping
Profiling Developer Options: Performance metrics on
screen or through ADB, Traces
Tracer for OpenGL ES: Visualize traces
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Intel GPA
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Intel Atom processors
More information: GPU, CPU, Battery usage
More detailed analysis
Identifies possible bottlenecks
Realtime
Works over Wifi
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Vendor specific tools
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Low level information
Different interface and capabilities for each vendor
Optimizations not always portable
PowerVR, Tegra, Adreno, etc.
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Bibliography
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https://www.khronos.org/opengles/
http://developer.android.com/guide/topics/graphics/ope
ngl.html
http://developer.android.com/training/graphics/opengl/i
ndex.html
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Keywords
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OpenGL
EGL
Fixed function pipeline
Shaders
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GLSurfaceView
Profiling
Tracer
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