我刚刚在Galaxy S3上尝试了developer.android.com上的原始OpenGL示例代码，但是屏幕上只有一个空白屏幕！我改变了清除颜色，屏幕背景也随之改变，但是我仍然看不到任何三角形或正方形，就像代码所示。
为了验证GPU的问题，我运行了一些从Play商店下载的编译应用程序，所有应用程序都运行良好。然后我尝试使用自己的GL代码按照教程进行操作，但是又得到了一个空白屏幕，然后我尝试了第三方示例代码，结果还是空白屏幕！
这到底是怎么回事？GL似乎除了背景颜色之外什么都没有绘制。
以下是我使用的Android示例代码链接。
为了验证GPU的问题，我运行了一些从Play商店下载的编译应用程序，所有应用程序都运行良好。然后我尝试使用自己的GL代码按照教程进行操作，但是又得到了一个空白屏幕，然后我尝试了第三方示例代码，结果还是空白屏幕！
这到底是怎么回事？GL似乎除了背景颜色之外什么都没有绘制。
以下是我使用的Android示例代码链接。
http://developer.android.com/shareables/training/OpenGLES.zip
这是代码
*
* 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:
* <ul>
* <li>{@link android.opengl.GLSurfaceView.Renderer#onSurfaceCreated}</li>
* <li>{@link android.opengl.GLSurfaceView.Renderer#onDrawFrame}</li>
* <li>{@link android.opengl.GLSurfaceView.Renderer#onSurfaceChanged}</li>
* </ul>
*/
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.
*
* <p><strong>Note:</strong> When developing shaders, use the checkGlError()
* method to debug shader coding errors.</p>
*
* @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:
*
* <pre>
* mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
* MyGLRenderer.checkGlError("glGetUniformLocation");</pre>
*
* 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;
}
}