java - Android openGL 示例给出空白屏幕

标签 java android opengl-es

我刚刚在 galaxy s3 上尝试了来自 developer.android.com 的原始开放式 GL 示例代码,它给我的只是一个空白屏幕!我改变了清晰的颜色,屏幕背景也改变了,但我仍然看不到代码指示的任何三角形或正方形。

为了验证 GPU 的任何问题,我从 Play 商店运行了一些编译的应用程序,并且都运行良好 然后我按照教程尝试使用自己的 gl 代码,再次出现黑屏,然后我尝试了第三方示例代码,猜猜又是什么黑屏!

这到底是怎么回事,GL除了背景色什么都画不出来

这是我使用的 android 示例代码的链接

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;
    }

}

最佳答案

对我来说,修复来自比较这两个矩阵

  1. 将 View (眼睛)设置为 Z 轴上的“-3”:

    Matrix.setLookAtM(mViewMatrix, 0, 0, 0, -3, 0f, 0f, 0f, 0f, 1.0f, 0.0f);

  2. 另一个设置应该可见的空间。在原始的 google 示例中,“近”平面设置为 3,“远”平面设置为 7:

    Matrix.frustumM(mProjectionMatrix, 0, -ratio, ratio, -1, 1, 3, 7);

这会将您的三角形置于显示空间的边缘。似乎这些间隔是开放的,因为在最边缘不会显示任何东西。

为了调整这一点,我只是将显示空间的定义更改为“near = 2”,如下所示: Matrix.frustumM(mProjectionMatrix, 0, -ratio, ratio, -1, 1, 2, 7);

砰的一声,突然间我开始做生意了;-)

我不确定为什么原始的谷歌示例设置为您实际上什么也看不到。可能是他们在教我们(很早就)初学者时提出了挑战;-) 希望这有帮助

关于java - Android openGL 示例给出空白屏幕,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/20219093/

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