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POSimple translation with opengl es 2.0 on Android
 

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  1. POSimple translation with opengl es 2.0 on Android
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    <p>I've look everywhere to understand how to translate shapes with openGl es 2.0 but I can't find the right way. Rotation and scaling work fine.</p> <p>I tried it with the android openGl es 2.0 tutorial but the shape is more distorded than translated.</p> <p>Here's the code (almost the same than the android code sample <a href="http://developer.android.com/shareables/training/OpenGLES.zip" rel="nofollow">http://developer.android.com/shareables/training/OpenGLES.zip</a>, except of the line to translate:</p> <pre><code>public class MyGLRenderer implements GLSurfaceView.Renderer { private static final String TAG = "MyGLRenderer"; private Triangle mTriangle; private Square mSquare; private final float[] mMVPMatrix = new float[16]; private final float[] mProjMatrix = new float[16]; private final float[] mVMatrix = new float[16]; private final float[] mRotationMatrix = new float[16]; // Declare as volatile because we are updating it from another thread public volatile float mAngle; @Override public void onSurfaceCreated(GL10 unused, EGLConfig config) { // Set the background frame color GLES20.glClearColor(0.0f, 0.0f, 0.0f, 1.0f); mTriangle = new Triangle(); mSquare = new Square(); } @Override public void onDrawFrame(GL10 unused) { // Draw background color GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT); // Set the camera position (View matrix) Matrix.setLookAtM(mVMatrix, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f); // Calculate the projection and view transformation Matrix.multiplyMM(mMVPMatrix, 0, mProjMatrix, 0, mVMatrix, 0); // Draw square mSquare.draw(mMVPMatrix); // Create a rotation for the triangle // long time = SystemClock.uptimeMillis() % 4000L; // float angle = 0.090f * ((int) time); Matrix.setRotateM(mRotationMatrix, 0, mAngle, 0, 0, -1.0f); // Combine the rotation matrix with the projection and camera view Matrix.multiplyMM(mMVPMatrix, 0, mRotationMatrix, 0, mMVPMatrix, 0); // Draw triangle mTriangle.draw(mMVPMatrix); } @Override public void onSurfaceChanged(GL10 unused, int width, int height) { // Adjust the viewport based on geometry changes, // such as screen rotation GLES20.glViewport(0, 0, width, height); float ratio = (float) width / height; // this projection matrix is applied to object coordinates // in the onDrawFrame() method Matrix.frustumM(mProjMatrix, 0, -ratio, ratio, -1, 1, 3, 7); } public static int loadShader(int type, String shaderCode){ // create a vertex shader type (GLES20.GL_VERTEX_SHADER) // or a fragment shader type (GLES20.GL_FRAGMENT_SHADER) int shader = GLES20.glCreateShader(type); // add the source code to the shader and compile it GLES20.glShaderSource(shader, shaderCode); GLES20.glCompileShader(shader); return shader; } /** * Utility method for debugging OpenGL calls. Provide the name of the call * just after making it: * * &lt;pre&gt; * mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor"); * MyGLRenderer.checkGlError("glGetUniformLocation");&lt;/pre&gt; * * If the operation is not successful, the check throws an error. * * @param glOperation - Name of the OpenGL call to check. */ public static void checkGlError(String glOperation) { int error; while ((error = GLES20.glGetError()) != GLES20.GL_NO_ERROR) { Log.e(TAG, glOperation + ": glError " + error); throw new RuntimeException(glOperation + ": glError " + error); } } } </code></pre> <p>And here's the square class with the translation transformation:</p> <pre><code>class Square { private final String vertexShaderCode = // This matrix member variable provides a hook to manipulate // the coordinates of the objects that use this vertex shader "uniform mat4 uMVPMatrix;" + "attribute vec4 vPosition;" + "void main() {" + // the matrix must be included as a modifier of gl_Position " gl_Position = vPosition * uMVPMatrix;" + "}"; private final String fragmentShaderCode = "precision mediump float;" + "uniform vec4 vColor;" + "void main() {" + " gl_FragColor = vColor;" + "}"; private final FloatBuffer vertexBuffer; private final ShortBuffer drawListBuffer; private final int mProgram; private int mPositionHandle; private int mColorHandle; private int mMVPMatrixHandle; // number of coordinates per vertex in this array static final int COORDS_PER_VERTEX = 3; static float squareCoords[] = { -0.5f, 0.5f, 0.0f, // top left -0.5f, -0.5f, 0.0f, // bottom left 0.5f, -0.5f, 0.0f, // bottom right 0.5f, 0.5f, 0.0f }; // top right private final short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex // Set color with red, green, blue and alpha (opacity) values float color[] = { 0.2f, 0.709803922f, 0.898039216f, 1.0f }; public Square() { // initialize vertex byte buffer for shape coordinates ByteBuffer bb = ByteBuffer.allocateDirect( // (# of coordinate values * 4 bytes per float) squareCoords.length * 4); bb.order(ByteOrder.nativeOrder()); vertexBuffer = bb.asFloatBuffer(); vertexBuffer.put(squareCoords); vertexBuffer.position(0); // initialize byte buffer for the draw list ByteBuffer dlb = ByteBuffer.allocateDirect( // (# of coordinate values * 2 bytes per short) drawOrder.length * 2); dlb.order(ByteOrder.nativeOrder()); drawListBuffer = dlb.asShortBuffer(); drawListBuffer.put(drawOrder); drawListBuffer.position(0); // prepare shaders and OpenGL program int vertexShader = MyGLRenderer.loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode); int fragmentShader = MyGLRenderer.loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode); mProgram = GLES20.glCreateProgram(); // create empty OpenGL Program GLES20.glAttachShader(mProgram, vertexShader); // add the vertex shader to program GLES20.glAttachShader(mProgram, fragmentShader); // add the fragment shader to program GLES20.glLinkProgram(mProgram); // create OpenGL program executables } public void draw(float[] mvpMatrix) { // Add program to OpenGL environment GLES20.glUseProgram(mProgram); // get handle to vertex shader's vPosition member mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition"); // Enable a handle to the triangle vertices GLES20.glEnableVertexAttribArray(mPositionHandle); // Prepare the triangle coordinate data GLES20.glVertexAttribPointer(mPositionHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false, vertexStride, vertexBuffer); // get handle to fragment shader's vColor member mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor"); // Set color for drawing the triangle GLES20.glUniform4fv(mColorHandle, 1, color, 0); // get handle to shape's transformation matrix mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix"); MyGLRenderer.checkGlError("glGetUniformLocation"); //TRANSLATION float[] transMatrix = new float[16]; Matrix.setIdentityM(transMatrix,0); Matrix.translateM(transMatrix,0,5.0f,0,0); Matrix.multiplyMM(transMatrix,0,mvpMatrix,0,transMatrix,0); // Apply the projection and view transformation GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, transMatrix, 0); MyGLRenderer.checkGlError("glUniformMatrix4fv"); // Draw the square GLES20.glDrawElements(GLES20.GL_TRIANGLES, drawOrder.length, GLES20.GL_UNSIGNED_SHORT, drawListBuffer); // Disable vertex array GLES20.glDisableVertexAttribArray(mPositionHandle); } } </code></pre> <p>I think it's related with the vertex shader code but I can't figure it out?</p>
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