Introduction to open_gl_in_android

Introduction To OpenGL in Android Tamillharasan Chandran & Krishnaprasad

Concepts Code! Basic Shapes Animation

Concepts OpenGL OpenGL ES OpenGL ES Not just Android!

Concepts Vector Graphics Raster Graphics Lines points, lines, polygons, Surface normals etc .. Grid of pixels

OpenGL Rendering Pipeline Simplified

Two Steps GLSurfaceView GLSurfaceView.Renderer

GLSurfaceView What is it? Why is it needed?

GLSurfaceView GLSurfaceView view = new GLSurfaceView(this); view.setEGLContextClientVersion(2); view.setRenderer(new SquareRenderer());

GLSurfaceView.Renderer What is it? Why is it needed? Create a Subclass of GLSurfaceView.Renderer Setup the view port

GLSurfaceView.Renderer public class SquareRenderer implements GLSurfaceView.Renderer { public void onSurfaceCreated(GL10 unused, EGLConfig config) { } public void onDrawFrame(GL10 unused) { } public void onSurfaceChanged(GL10 unused, int width, int height) { } } GLES20.glViewport(0, 0, width, height); GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT); GLES20.glClearColor(0.5f, 0.5f, 0.5f, 1.0f);

There you go!! Your First Android OpenGL App

Define a Square All the 2D/ 3D objects needs to be defined using Primitives. Vertex - A vertex is a point where two or more edges meet Edges - A vertex (vertices in plural) is the smallest building block of 3D model. A vertex is a point where two or more edges meet Face is a triangle. Face is a surface between three corner vertices and three surrounding edges.

-0.5f, -0.5f, 0.0f, // Bottom Left 0.5f, -0.5f, 0.0f, // Bottom Right -0.5f, 0.5f, 0.0f, // Top Left 0.5f, 0.5f, 0.0f, // Top Right

private void initShapes(){ float squareCoords[] = { //The coordinates }; // initialize vertex Buffer for square ByteBuffer vbb = ByteBuffer.allocateDirect(squareCoords.length * 4); vbb.order(ByteOrder.nativeOrder()); squareVB = vbb.asFloatBuffer(); squareVB.put(squareCoords); squareVB.position(0); }

Draw Methods glDrawArrays() glDrawElements() Available Primitives in OpenGL ES GL_POINTS GL_LINE_STRIP GL_LINE_LOOP GL_LINES GL_TRIANGLES GL_TRIANGLE_STRIP GL_TRIANGLE_FAN Draw a square

GL_POINTS GL_LINES GL_LINE_STRIP GL_TRIANGLES GL_TRIANGLE_STRIP GL_TRIANGLE_FAN

Shader Programs Vertex Shader Fragment Shader Loading the shader objects Attaching the Shader objects to Shader program Linking the program to create executable shader program

Vertex Shader Fragment Shader attribute vec4 vertexPosition; void main(){ gl_Position = vertexPosition; } precision mediump float; void main(){ gl_FragColor = vec4(0.5, 0.5, 0.5, 1.0); }

Loading the Shader GLES20.glCompileShader(vertexShader); GLES20.GL_FRAGMENT_SHADER int vertexShader = GLES20.glCreateShader(GLES20. GL_VERTEX_SHADER ); GLES20.glShaderSource(vertexShader, shaderCode);

Compiling and Linking the Shader program shaderProgram = GLES20.glCreateProgram(); GLES20.glAttachShader(shaderProgram, vertexShader); GLES20.glAttachShader(shaderProgram, fragmentShader); GLES20.glLinkProgram(shaderProgram);

attributePositionHandle = GLES20. glGetAttribLocation (shaderProgram,"vertexPosition");

Drawing the square GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT); GLES20.glUseProgram(shaderProgram); GLES20.glVertexAttribPointer(attributePositionHandle, 3, GLES20.GL_FLOAT, false, 12, squareVB); GLES20.glEnableVertexAttribArray(attributePositionHandle); GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4);

Apply Projection and Camera View Square Coordinate system is a mapped to non-square screen To display Objects in correct proportions on different device screens

Setting up the projection private float[] MVPMatrix = new float[16]; private float[] projectionMatrix = new float[16]; //-- float ratio = (float) width / height; Matrix.frustumM(projectionMatrix, 0, -ratio, ratio, -1, 1, 3, 7); Matrix.setLookAtM(ViewMatrix, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);

Applying the MVP matrix uniform mat4 MVPMatrix ; attribute vec4 vertexPosition; void main(){ gl_Position = MVPMatrix * vertexPosition; }

Applying the MVP matrix(Contd) ... Matrix.multiplyMM(MVPMatrix, 0, projectionMatrix, 0, viewMatrix, 0); GLES20.glUniformMatrix4fv(MVPMatrixHandle, 1, false, MVPMatrix, 0); // Draw the square GLES20.glDrawArrays(GLES20.GL_TRIANGLE_STRIP, 0, 4); ...

Giving life to the objects (Animation)

Animation Matrix.multiplyMM(modelViewProjectionMatrix, 0, projectionMatrix, 0, modelMatrix, 0); GLES20.glUniformMatrix4fv(MVPMatrixHandle, 1, false, modelViewProjectionMatrix, 0); long time = SystemClock.uptimeMillis() % 4000L; float angle = 0.090f * ((int) time); Matrix.setRotateM(modelMatrix, 0, angle, 0, 0, 1.0f); Matrix.multiplyMM(modelViewProjectionMatrix,0,projectionMatrix,0,viewMatrix,0);

Introduction to open_gl_in_android

More Related Content

What's hot (20)

Viewers also liked (20)

Similar to Introduction to open_gl_in_android (20)

Recently uploaded (20)

Introduction to open_gl_in_android

Editor's Notes