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POOpenGL ES tutorial for android doesn't seem to work
 

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    <p>I've been following the tutorial at <a href="http://developer.android.com/resources/tutorials/opengl/opengl-es20.html" rel="noreferrer">http://developer.android.com/resources/tutorials/opengl/opengl-es20.html</a> for OpenGL ES on android. I've gotten to the, "Apply Projection and Camera View" section however I always seem to get a blank screen with no triangle, the previous section worked perfectly fine. I also tried just copy pasting the entire tutorial into my code but got the same result. Changing the line:</p> <pre><code>gl_Position = uMVPMatrix * vPosition; </code></pre> <p>to:</p> <pre><code>gl_Position = vPosition; </code></pre> <p>puts the application back to the first section (triangle stretches depending on screen orientation). Any idea what the problem is? Here's the code I have so far just in case I missed something:</p> <pre><code>public class GLTest20Renderer implements Renderer { 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; \n" + "attribute vec4 vPosition; \n" + "void main(){ \n" + // the matrix must be included as a modifier of gl_Position " gl_Position = uMVPMatrix * vPosition; \n" + "} \n"; private final String fragmentShaderCode = "precision mediump float; \n" + "void main(){ \n" + " gl_FragColor = vec4 (0.63671875, 0.76953125, 0.22265625, 1.0); \n" + "} \n"; private FloatBuffer triangleVB; private int mProgram; private int maPositionHandle; private int muMVPMatrixHandle; private float[] mMVPMatrix = new float[16]; private float[] mMMatrix = new float[16]; private float[] mVMatrix = new float[16]; private float[] mProjMatrix = new float[16]; public void onSurfaceCreated(GL10 unused, EGLConfig config) { GLES20.glClearColor(0.5f, 0.5f, 0.5f, 1.0f); initShapes(); int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode); int fragmentShader = 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); // creates OpenGL program executables // get handle to the vertex shader's vPosition member maPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition"); } public void onDrawFrame(GL10 unused) { GLES20.glClear( GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT ); // Add program to OpenGL environment GLES20.glUseProgram(mProgram); // Prepare the triangle data GLES20.glVertexAttribPointer(maPositionHandle, 3, GLES20.GL_FLOAT, false, 12, triangleVB); GLES20.glEnableVertexAttribArray(maPositionHandle); // Apply a ModelView Projection transformation Matrix.multiplyMM(mMVPMatrix, 0, mProjMatrix, 0, mVMatrix, 0); GLES20.glUniformMatrix4fv(muMVPMatrixHandle, 1, false, mMVPMatrix, 0); // Draw the triangle GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3); } public void onSurfaceChanged(GL10 unused, int width, int height) { GLES20.glViewport(0, 0, width, height); float ratio = (float) width / height; Matrix.frustumM(mProjMatrix, 0, -ratio, ratio, -1, 1, 3, 7); muMVPMatrixHandle = GLES20.glGetUniformLocation(mProgram, "uMVPMatrix"); Matrix.setLookAtM(mVMatrix, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f); } private void initShapes() { float triangleCoords[] = { // X, Y, Z -0.5f, -0.25f, 0, 0.5f, -0.25f, 0, 0.0f, 0.559016994f, 0 }; // initialize vertex Buffer for triangle ByteBuffer vbb = ByteBuffer.allocateDirect( // (# of coordinate values * 4 bytes per float) triangleCoords.length * 4); vbb.order(ByteOrder.nativeOrder());// use the device hardware's native byte order triangleVB = vbb.asFloatBuffer(); // create a floating point buffer from the ByteBuffer triangleVB.put(triangleCoords); // add the coordinates to the FloatBuffer triangleVB.position(0); // set the buffer to read the first coordinate } private 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; } } </code></pre> <p>I'm running all this on a Samsung Galaxy S2.</p>
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    1. COWell, I managed to fix it by changing the near point in the look at to 2: Matrix.frustumM(mProjMatrix, 0, -ratio, ratio, -1, 1, 2, 7); rather than 3, not sure if this is an error on their part or if I still missed something.
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    2. COare you sure if the device supports opengl2.0?
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    3. COYep, I've run OpenGL2.0 applications on it before
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