Android OpenGL ES 2.0 (六) 混合blending

现在来看看的blending效果。

blending分为Additive blending，Multiplicative blending和Interpolative blending。

对应的方法分别为

glBlendFunc(GL_ONE, GL_ONE)，

glBlendFunc(GL_DST_COLOR, GL_ZERO)和

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)。

现在就用Additive blending来写个例子。

这里的GLSurfaceView要处理点击消息来开启和关闭blending效果，所以单独提取一个类。

Test6SurfaceView.java

package com.android.jayce.test;

import android.content.Context;
import android.opengl.GLSurfaceView;
import android.view.MotionEvent;

public class Test6SurfaceView extends GLSurfaceView
{
    private Test6Renderer mRenderer;
    
    public Test6SurfaceView(Context context) {
        super(context);
        // TODO Auto-generated constructor stub
    }
    
    public boolean onTouchEvent(MotionEvent event)
    {
        if(event != null)
        {
            if(event.getAction() == MotionEvent.ACTION_DOWN)
            {
                if(mRenderer != null)
                {
                    queueEvent(new Runnable(){

                        @Override
                        public void run() {
                            // TODO Auto-generated method stub
                            mRenderer.switchMode();
                        }});
                    return true;
                }
            }
        }
        return super.onTouchEvent(event);
    }
    
    public void setRenderer(Test6Renderer renderer)
    {
        mRenderer = renderer;
        super.setRenderer(renderer);
    }
    
}

Renderer里面开关blending效果在switchMode里。

开启是：
            GLES20.glDisable(GLES20.GL_CULL_FACE);
            GLES20.glDisable(GLES20.GL_DEPTH_TEST);
            GLES20.glEnable(GLES20.GL_BLEND);
            GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE);

关闭是：

　　　　 GLES20.glEnable(GLES20.GL_CULL_FACE);
            GLES20.glEnable(GLES20.GL_DEPTH_TEST);
            GLES20.glDisable(GLES20.GL_BLEND);

看完整代码：

Test6Renderer.java

package com.android.jayce.test;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.opengles.GL10;

import com.learnopengles.android.common.ShapeBuilder;

import android.opengl.GLES20;
import android.opengl.Matrix;
import android.opengl.GLSurfaceView;
import android.os.SystemClock;

public class Test6Renderer implements GLSurfaceView.Renderer
{
    private static final int BYTES_PER_FLOAT = 4;
    private final FloatBuffer mCubePositions;
    private final FloatBuffer mCubeColors;
    private float[] mMVPMatrix = new float[16];
    private float[] mViewMatrix = new float[16];
    private float[] mModelMatrix = new float[16];
    private float[] mProjectionMatrix = new float[16];
    private int mMVPMatrixHandle;
    private int mPositionHandle;
    private int mColorHandle;
    private int mProgramHandle;
    private final int POSITION_DATA_SIZE = 3;
    private final int COLOR_DATA_SIZE = 4;
    private boolean mBlending = true;
    
    public Test6Renderer()
    {
        final float[] p1p = {-1.0f, 1.0f, 1.0f};                    
        final float[] p2p = {1.0f, 1.0f, 1.0f};
        final float[] p3p = {-1.0f, -1.0f, 1.0f};
        final float[] p4p = {1.0f, -1.0f, 1.0f};
        final float[] p5p = {-1.0f, 1.0f, -1.0f};
        final float[] p6p = {1.0f, 1.0f, -1.0f};
        final float[] p7p = {-1.0f, -1.0f, -1.0f};
        final float[] p8p = {1.0f, -1.0f, -1.0f};
        final float[] cubePosition = ShapeBuilder.generateCubeData(p1p, p2p, p3p, p4p, p5p, p6p, p7p, p8p, p1p.length);
        
        final float[] p1c = {1.0f, 0.0f, 0.0f, 1.0f};        // red            
        final float[] p2c = {1.0f, 0.0f, 1.0f, 1.0f};        // magenta
        final float[] p3c = {0.0f, 0.0f, 0.0f, 1.0f};        // black
        final float[] p4c = {0.0f, 0.0f, 1.0f, 1.0f};        // blue
        final float[] p5c = {1.0f, 1.0f, 0.0f, 1.0f};        // yellow
        final float[] p6c = {1.0f, 1.0f, 1.0f, 1.0f};        // white
        final float[] p7c = {0.0f, 1.0f, 0.0f, 1.0f};        // green
        final float[] p8c = {0.0f, 1.0f, 1.0f, 1.0f};        // cyan
        
        final float[] cubeColor = ShapeBuilder.generateCubeData(p1c, p2c, p3c, p4c, p5c, p6c, p7c, p8c, p1c.length);
        
        mCubePositions = ByteBuffer.allocateDirect(cubePosition.length * BYTES_PER_FLOAT)
                .order(ByteOrder.nativeOrder()).asFloatBuffer();
        mCubePositions.put(cubePosition).position(0);
        mCubeColors = ByteBuffer.allocateDirect(cubeColor.length * BYTES_PER_FLOAT)
                .order(ByteOrder.nativeOrder()).asFloatBuffer();
        mCubeColors.put(cubeColor).position(0);
    }
    
    @Override
    public void onDrawFrame(GL10 gl) {
        // TODO Auto-generated method stub
        if (mBlending)
        {
            GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT);
        }
        else
        {
            GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
        }
        long time = SystemClock.uptimeMillis() % 10000L;        
        float angleInDegrees = (360.0f / 10000.0f) * ((int) time);
        GLES20.glUseProgram(mProgramHandle);
        mMVPMatrixHandle = GLES20.glGetUniformLocation(mProgramHandle, "u_MVPMatrix");
        mPositionHandle = GLES20.glGetAttribLocation(mProgramHandle, "a_Position");
        mColorHandle = GLES20.glGetAttribLocation(mProgramHandle, "a_Color");
        
        Matrix.setIdentityM(mModelMatrix, 0);
        Matrix.translateM(mModelMatrix, 0, 0.0f, 0.0f, -5.0f);
        Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 1.0f, 1.0f, 0.0f);   
        drawCube(mCubePositions, mCubeColors);
    }

    public void switchMode()
    {        
        mBlending = !mBlending;
        
        if (mBlending)
        {
            // No culling of back faces
            GLES20.glDisable(GLES20.GL_CULL_FACE);
            
            // No depth testing
            GLES20.glDisable(GLES20.GL_DEPTH_TEST);
            
            // Enable blending
            GLES20.glEnable(GLES20.GL_BLEND);
            GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE);            
        }
        else
        {
            // Cull back faces
            GLES20.glEnable(GLES20.GL_CULL_FACE);
            
            // Enable depth testing
            GLES20.glEnable(GLES20.GL_DEPTH_TEST);
            
            // Disable blending
            GLES20.glDisable(GLES20.GL_BLEND);
        }
    }
    
    private void drawCube(final FloatBuffer cubePositionsBuffer, final FloatBuffer cubeColorsBuffer)
    {
        cubePositionsBuffer.position(0);
        GLES20.glVertexAttribPointer(mPositionHandle, POSITION_DATA_SIZE, GLES20.GL_FLOAT, false, 0, cubePositionsBuffer);
        GLES20.glEnableVertexAttribArray(mPositionHandle);
        
        cubeColorsBuffer.position(0);
        GLES20.glVertexAttribPointer(mColorHandle, COLOR_DATA_SIZE, GLES20.GL_FLOAT, false, 0, cubeColorsBuffer);
        GLES20.glEnableVertexAttribArray(mColorHandle);
        Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);   
        Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
        
        GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
        GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 36);
    }
    
    @Override
    public void onSurfaceChanged(GL10 gl, int width, int height) {
        // TODO Auto-generated method stub
        GLES20.glViewport(0, 0, width, height);
        
        final float ratio = (float) width / height;
        final float left = -ratio;
        final float right = ratio;
        final float bottom = -1.0f;
        final float top = 1.0f;
        final float near = 1.0f;
        final float far = 10.0f;
        
        Matrix.frustumM(mProjectionMatrix, 0, left, right, bottom, top, near, far);
    }

    @Override
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        // TODO Auto-generated method stub
        GLES20.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        GLES20.glDisable(GLES20.GL_CULL_FACE);
        GLES20.glDisable(GLES20.GL_DEPTH_TEST);
        
        GLES20.glEnable(GLES20.GL_BLEND);
        GLES20.glBlendFunc(GLES20.GL_ONE, GLES20.GL_ONE);
        
        // Position the eye behind the origin.
        final float eyeX = 0.0f;
        final float eyeY = 0.0f;
        final float eyeZ = -0.5f;

        // We are looking toward the distance
        final float lookX = 0.0f;
        final float lookY = 0.0f;
        final float lookZ = -5.0f;

        // Set our up vector. This is where our head would be pointing were we holding the camera.
        final float upX = 0.0f;
        final float upY = 1.0f;
        final float upZ = 0.0f;

        // Set the view matrix. This matrix can be said to represent the camera position.
        // NOTE: In OpenGL 1, a ModelView matrix is used, which is a combination of a model and
        // view matrix. In OpenGL 2, we can keep track of these matrices separately if we choose.
        Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ, upX, upY, upZ);
        
        final String vertexShader =
                "uniform mat4 u_MVPMatrix;      \n"        // A constant representing the combined model/view/projection matrix.
                
              + "attribute vec4 a_Position;     \n"        // Per-vertex position information we will pass in.
              + "attribute vec4 a_Color;        \n"        // Per-vertex color information we will pass in.              
              + "varying vec4 v_Color;          \n"        // This will be passed into the fragment shader.
              
              + "void main()                    \n"        // The entry point for our vertex shader.
              + "{                              \n"
              + "   v_Color = a_Color;          \n"        // Pass the color through to the fragment shader. 
                                                          // It will be interpolated across the triangle.
              + "   gl_Position = u_MVPMatrix   \n"     // gl_Position is a special variable used to store the final position.
              + "               * a_Position;   \n"     // Multiply the vertex by the matrix to get the final point in                                                                      
              + "}                              \n";    // normalized screen coordinates.
            
        final String fragmentShader =
                "precision mediump float;       \n"        // Set the default precision to medium. We don't need as high of a 
                                                        // precision in the fragment shader.                
              + "varying vec4 v_Color;          \n"        // This is the color from the vertex shader interpolated across the 
                                                          // triangle per fragment.              
              + "void main()                    \n"        // The entry point for our fragment shader.
              + "{                              \n"
              + "   gl_FragColor = v_Color;     \n"        // Pass the color directly through the pipeline.          
              + "}                              \n";    
            
        int vertexShaderHandle = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
        if(vertexShaderHandle != 0)
        {
            GLES20.glShaderSource(vertexShaderHandle, vertexShader);
            GLES20.glCompileShader(vertexShaderHandle);
            
            final int[] compileStatus = new int[1];
            GLES20.glGetShaderiv(vertexShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
            
            if(compileStatus[0] == 0)
            {
                GLES20.glDeleteShader(vertexShaderHandle);
                vertexShaderHandle = 0;
            }
        }
        
        if(vertexShaderHandle == 0)
        {
            throw new RuntimeException("failed to creating vertex shader");
        }
        
        int fragmentShaderHandle = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
        if(fragmentShaderHandle != 0)
        {
            GLES20.glShaderSource(fragmentShaderHandle, fragmentShader);
            GLES20.glCompileShader(fragmentShaderHandle);
            
            final int[] compileStatus = new int[1];
            GLES20.glGetShaderiv(fragmentShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
            
            if(compileStatus[0] == 0)
            {
                GLES20.glDeleteShader(fragmentShaderHandle);
                fragmentShaderHandle = 0;
            }
            
        }
        
        if(fragmentShaderHandle == 0)
        {
            throw new RuntimeException("failed to create fragment shader");
        }
        
        mProgramHandle = GLES20.glCreateProgram();
        if(mProgramHandle != 0)
        {
            GLES20.glAttachShader(mProgramHandle, vertexShaderHandle);
            GLES20.glAttachShader(mProgramHandle, fragmentShaderHandle);
            
            GLES20.glBindAttribLocation(mProgramHandle, 0, "a_Position");
            GLES20.glBindAttribLocation(mProgramHandle, 1, "a_Color");
            
            GLES20.glLinkProgram(mProgramHandle);
            
            final int[] linkStatus = new int[1];
            GLES20.glGetProgramiv(mProgramHandle, GLES20.GL_LINK_STATUS, linkStatus, 0);
            
            if(linkStatus[0] == 0)
            {
                GLES20.glDeleteProgram(mProgramHandle);
                mProgramHandle = 0;
            }
        }
        
        if(mProgramHandle == 0)
        {
            throw new RuntimeException("failed to create program");
        }
        
    }
    
}

构造方法里用了内置方法来生成CubePosition和CubeColor。

来看看效果：

开启blending效果：

    

关闭blending效果：