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POAndroid openGL example gives blank screen
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  1. POAndroid openGL example gives blank screen
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    copied!<p>I just tried the original open GL example code from developer.android.com on a galaxy s3 and all It gave me was a blank screen! I changed the clear color and the screen background changed but I still can't see any triangle or square as the code indicates.</p> <p>To verify any problem with GPU I ran some compiled apps from play store and all run fine then I tried with my own gl code following the tutorial and again It gave a blank screen then I tried a third party example code and guess what again blank screen!</p> <p>What the hell is wrong the GL doesn't seem to draw anything except background color</p> <p>Here's a link to android example code I used</p> <p><a href="http://developer.android.com/shareables/training/OpenGLES.zip" rel="noreferrer">http://developer.android.com/shareables/training/OpenGLES.zip</a></p> <p>This is the code</p> <pre><code> * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.example.android.opengl; import java.nio.ByteBuffer; import java.nio.ByteOrder; import java.nio.FloatBuffer; import android.opengl.GLES20; /** * A two-dimensional triangle for use as a drawn object in OpenGL ES 2.0. */ public class Triangle { 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 // Note that the uMVPMatrix factor *must be first* in order // for the matrix multiplication product to be correct. " gl_Position = uMVPMatrix * vPosition;" + "}"; private final String fragmentShaderCode = "precision mediump float;" + "uniform vec4 vColor;" + "void main() {" + " gl_FragColor = vColor;" + "}"; private final FloatBuffer vertexBuffer; 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 triangleCoords[] = { // in counterclockwise order: 5.0f, 0.622008459f, 0.0f, // top -5.5f, -0.311004243f, 0.0f, // bottom left 5.5f, -0.311004243f, 0.0f // bottom right }; private final int vertexCount = triangleCoords.length / COORDS_PER_VERTEX; private final int vertexStride = COORDS_PER_VERTEX * 4; // 4 bytes per vertex float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 0.0f }; /** * Sets up the drawing object data for use in an OpenGL ES context. */ public Triangle() { // initialize vertex byte buffer for shape coordinates ByteBuffer bb = ByteBuffer.allocateDirect( // (number of coordinate values * 4 bytes per float) triangleCoords.length * 4); // use the device hardware's native byte order bb.order(ByteOrder.nativeOrder()); // create a floating point buffer from the ByteBuffer vertexBuffer = bb.asFloatBuffer(); // add the coordinates to the FloatBuffer vertexBuffer.put(triangleCoords); // set the buffer to read the first coordinate vertexBuffer.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 } /** * Encapsulates the OpenGL ES instructions for drawing this shape. * * @param mvpMatrix - The Model View Project matrix in which to draw * this shape. */ 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"); // Apply the projection and view transformation GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mvpMatrix, 0); MyGLRenderer.checkGlError("glUniformMatrix4fv"); // Draw the triangle GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, vertexCount); // Disable vertex array GLES20.glDisableVertexAttribArray(mPositionHandle); } } /* * Copyright (C) 2011 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.example.android.opengl; import javax.microedition.khronos.egl.EGLConfig; import javax.microedition.khronos.opengles.GL10; import android.opengl.GLES20; import android.opengl.GLSurfaceView; import android.opengl.Matrix; import android.util.Log; /** * Provides drawing instructions for a GLSurfaceView object. This class * must override the OpenGL ES drawing lifecycle methods: * &lt;ul&gt; * &lt;li&gt;{@link android.opengl.GLSurfaceView.Renderer#onSurfaceCreated}&lt;/li&gt; * &lt;li&gt;{@link android.opengl.GLSurfaceView.Renderer#onDrawFrame}&lt;/li&gt; * &lt;li&gt;{@link android.opengl.GLSurfaceView.Renderer#onSurfaceChanged}&lt;/li&gt; * &lt;/ul&gt; */ public class MyGLRenderer implements GLSurfaceView.Renderer { private static final String TAG = "MyGLRenderer"; private Triangle mTriangle; private Square mSquare; // mMVPMatrix is an abbreviation for "Model View Projection Matrix" private final float[] mMVPMatrix = new float[16]; private final float[] mProjectionMatrix = new float[16]; private final float[] mViewMatrix = new float[16]; private final float[] mRotationMatrix = new float[16]; private float mAngle; @Override public void onSurfaceCreated(GL10 unused, EGLConfig config) { // Set the background frame color GLES20.glClearColor(0.0f, 0.0f, 0.2f, 1.0f); mTriangle = new Triangle(); mSquare = new Square(); } @Override public void onDrawFrame(GL10 unused) { float[] scratch = new float[16]; // Draw background color GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT); // Set the camera position (View matrix) Matrix.setLookAtM(mViewMatrix, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f); // Calculate the projection and view transformation Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mViewMatrix, 0); // Draw square mSquare.draw(mMVPMatrix); // Create a rotation for the triangle // Use the following code to generate constant rotation. // Leave this code out when using TouchEvents. // 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 // Note that the mMVPMatrix factor *must be first* in order // for the matrix multiplication product to be correct. Matrix.multiplyMM(scratch, 0, mMVPMatrix, 0, mRotationMatrix, 0); // Draw triangle mTriangle.draw(scratch); } @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(mProjectionMatrix, 0, -ratio, ratio, -1, 1, 3, 7); } /** * Utility method for compiling a OpenGL shader. * * &lt;p&gt;&lt;strong&gt;Note:&lt;/strong&gt; When developing shaders, use the checkGlError() * method to debug shader coding errors.&lt;/p&gt; * * @param type - Vertex or fragment shader type. * @param shaderCode - String containing the shader code. * @return - Returns an id for the shader. */ 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); } } /** * Returns the rotation angle of the triangle shape (mTriangle). * * @return - A float representing the rotation angle. */ public float getAngle() { return mAngle; } /** * Sets the rotation angle of the triangle shape (mTriangle). */ public void setAngle(float angle) { mAngle = angle; } } </code></pre>
 

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