![Drawing a Square
draw() {
float coords[] = { .... };
vertex 'buffer' created with the coords
glVertexPointer(buffer) :
}
glDrawArrays(TRIANGLE_STRIP ...);
,](https://image.slidesharecdn.com/highperformancegraphicsandcompute-openglesandrenderscript-140224234438-phpapp02/85/High-performance-graphics-and-computation-OpenGL-ES-and-RenderScript-12-320.jpg)
![Drawing a Square
draw() {
float squareCoords[] = { .... };
ByteBuffer vbb = ....
squareVB = vbb.asFloatBuffer();
squareVB.put(squareCoords);
gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer);
}
gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP 0, vertices.length / 3);
,
Full code:
https://github.com/arvind-devaraj/androidopengles/blob/master/3_SquareRenderer/src/com/example/graphics1/Square.java](https://image.slidesharecdn.com/highperformancegraphicsandcompute-openglesandrenderscript-140224234438-phpapp02/85/High-performance-graphics-and-computation-OpenGL-ES-and-RenderScript-13-320.jpg)
High performance graphics and computation - OpenGL ES and RenderScript
- 1. High Performance Graphics and Compute OpenGLES and RenderScript Arvind Devaraj
- 2. Agenda ● Introduction : Graphics terms ● Graphics on GPU ● OpenGL Android Graphics ● Graphics Pipeline ● Shaders ● High Performance Compute on GPU ● RenderScript
- 3. Graphics Terms ● ● ● OpenGLES : Graphics API for doing 3D operations on GPU / CPU Primitives : lines, point, triangles Texture : make the image realistic by adding bitmap
- 4. CPU versus GPU ● CPU – good at executing sequential code – ● Handles branches well – Same code, multiple data GPU – Parallelism (ideal for image rendering)
- 7. OpenGLES Android Graphics ● Graphics Library for 3D
- 8. Android Graphics Classes GLSurfaceView GLSurfaceView.Renderer View ➢ - connects SurfaceView to OpenGLES library Renderer - responsible for making OpenGL calls to render a frame ➢
- 9. GLSurfaceView GLSurfaceView view = new GLSurfaceView(this); view.setRenderer(new SquareRenderer());
- 10. GLSurfaceView.Renderer ● The renderer is responsible for making OpenGL calls to render a frame. – onDrawFrame() responsible for drawing the current frame – OnSurfaceChanged() called when surface size changes – OnSurfaceCreated() called when surface is created
- 11. GLSurfaceView.Renderer public class SquareRenderer implements GLSurfaceView.Renderer { public void onSurfaceCreated(GL10 unused, EGLConfig config) { Code when surface is created } public void onDrawFrame(GL10 unused) { Code for drawing the frame ( Square ) } public void onSurfaceChanged(GL10 unused, int width, int height) { When surface is changed (rotated etc) } }
- 12. Drawing a Square draw() { float coords[] = { .... }; vertex 'buffer' created with the coords glVertexPointer(buffer) : } glDrawArrays(TRIANGLE_STRIP ...); ,
- 13. Drawing a Square draw() { float squareCoords[] = { .... }; ByteBuffer vbb = .... squareVB = vbb.asFloatBuffer(); squareVB.put(squareCoords); gl.glVertexPointer(3, GL10.GL_FLOAT, 0, vertexBuffer); } gl.glDrawArrays(GL10.GL_TRIANGLE_STRIP 0, vertices.length / 3); , Full code: https://github.com/arvind-devaraj/androidopengles/blob/master/3_SquareRenderer/src/com/example/graphics1/Square.java
- 15. Shaders ● Shaders are programs that execute on the GPU ● Shader programs operate on – Each vertex – Each pixel
- 16. Shader Programs • Vertex Shader – operates on each vertex • Fragment Shader – operates on each pixel • Shaders are compiled and linked ( like any program ) • Executable is sent to the GPU
- 18. Vertex Shader attribute vec4 vertexPosition; void main(){ gl_Position = vertexPosition; } Fragment Shader precision mediump float; void main(){ gl_FragColor = vec4(0.5, 0.5, 0.5, 1.0); }
- 20. CPU – GPU communication
- 21. GPU for General Programs ● Graphics is accelerated by the GPU ● Can GPU accelerate other programs ? – ● e.g. Matrix multiply, encryption OpenCL, CUDA, Renderscript are API – used for general purpose GPU
- 22. RenderScript ● A high level API to access GPU ● Provides high performance Compute ● Provides uniform API across multiple SoC ● Alternative is NDK (but NDK is platform specific)
- 23. RenderScript – Use cases ● What functions can be accelerated – Graphics – Image Processing – Encryption – Signal processing – Mathematical functions
- 25. RenderScript – CPU side Class Hello extends Activity { Allocation input; Allocation output; RenderScript rs = new RenderScript() ScriptC_func script = new ScriptC_func(...) } script.forEach_root(input, output)
- 26. RenderScript – GPU side Hello.rs void root (char *in , char *out) { *out = *in * 2 }
- 27. RenderScript ● ● Advantages : Compared to NDK, provides an easy device agnostic way to accelerate performance on GPU Disadvantages : C99 standard, debugging is restricted
- 28. Renderscipt - Summary ● Renderscript is an API to access GPU ● Used for High Performance ● High Performance Compute / Graphics ● Compute, Math , FFT, convolution, Signal processing ● Support Graphics – but not a replacement for OpenGL ● Works on all GPUs ( if supported by SoC ) otherwise on CPU ● ●