Android OpenGL ES 2.0 (一) 画三角形

看Opengl es的相关知识也有几天了。开始动手跟着例子写代码了。现在就先写个最简单的，画个三角形吧，里面包含了最基本的vertex shader和fragment shader的用法.

Activity里设置opengl es版本为2.0，如果没设，会默认用1.0，然后运行会报API未实现exception.

TestActivity.java

package com.android.jayce.test;

import android.app.Activity;
import android.app.ActivityManager;
import android.content.Context;
import android.content.pm.ConfigurationInfo;
import android.opengl.GLSurfaceView;
import android.opengl.GLSurfaceView.Renderer;
import android.os.Bundle;

public class TestActivity extends Activity
{
    private GLSurfaceView mGLSurfaceView;
    
    public void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        mGLSurfaceView = new GLSurfaceView(this);
        final ActivityManager activityManager = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);
        final ConfigurationInfo configInfo = activityManager.getDeviceConfigurationInfo();
        if(configInfo.reqGlEsVersion >= 0x20000)
        {
            mGLSurfaceView.setEGLContextClientVersion(2);
            Renderer renderer = new TestRenderer();
            mGLSurfaceView.setRenderer(renderer);
        }
        
        setContentView(mGLSurfaceView);
    }
    
    @Override
    protected void onResume() 
    {
        // The activity must call the GL surface view's onResume() on activity onResume().
        super.onResume();
        mGLSurfaceView.onResume();
    }

    @Override
    protected void onPause() 
    {
        // The activity must call the GL surface view's onPause() on activity onPause().
        super.onPause();
        mGLSurfaceView.onPause();
    }    
}

然后是Renderer的实现，参数很少，只有点坐标，颜色

TestRenderer.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 android.opengl.GLES20;
import android.opengl.Matrix;
import android.opengl.GLSurfaceView;


public class TestRenderer implements GLSurfaceView.Renderer
{

    private final FloatBuffer mTriangle1Vertices;
    private static final int BYTES_PER_FLOAT = 4;
    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 final int POSITION_OFFSET = 0;
    private final int COLOR_OFFSET = 3;
    private final int POSITION_DATA_SIZE = 3;
    private final int COLOR_DATA_SIZE = 4;
    private final int STRIDE = 7 * BYTES_PER_FLOAT;
    
    public TestRenderer()
    {
        final float[] triangle1VerticesData = {
                // X, Y, Z, 
                // R, G, B, A
                -0.5f, -0.25f, 0.0f, 
                1.0f, 0.0f, 0.0f, 1.0f,
                
                0.5f, -0.25f, 0.0f,
                0.0f, 0.0f, 1.0f, 1.0f,
                
                0.0f, 0.559016994f, 0.0f, 
                0.0f, 1.0f, 0.0f, 1.0f};
        
        mTriangle1Vertices = ByteBuffer.allocateDirect(triangle1VerticesData.length * BYTES_PER_FLOAT)
                .order(ByteOrder.nativeOrder()).asFloatBuffer();
        mTriangle1Vertices.put(triangle1VerticesData).position(0);
    }
    
    @Override
    public void onDrawFrame(GL10 gl) {
        // TODO Auto-generated method stub
        GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);
        
        Matrix.setIdentityM(mModelMatrix, 0);
        drawTriandle(mTriangle1Vertices);
    }

    private void drawTriandle(final FloatBuffer triangleBuffer)
    {
        triangleBuffer.position(POSITION_OFFSET);
        GLES20.glVertexAttribPointer(mPositionHandle, POSITION_DATA_SIZE, GLES20.GL_FLOAT, false, STRIDE, triangleBuffer);
        GLES20.glEnableVertexAttribArray(mPositionHandle);
        
        triangleBuffer.position(COLOR_OFFSET);
        GLES20.glVertexAttribPointer(mColorHandle, COLOR_DATA_SIZE, GLES20.GL_FLOAT, false, STRIDE, triangleBuffer);
        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, 3);
    }
    
    @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(0f, 0f, 0f, 1f);
        
        // Position the eye behind the origin.
        final float eyeX = 0.0f;
        final float eyeY = 0.0f;
        final float eyeZ = 1.5f;

        // 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");
        }
        
        int programHandle = GLES20.glCreateProgram();
        if(programHandle != 0)
        {
            GLES20.glAttachShader(programHandle, vertexShaderHandle);
            GLES20.glAttachShader(programHandle, fragmentShaderHandle);
            
            GLES20.glBindAttribLocation(programHandle, 0, "a_Position");
            GLES20.glBindAttribLocation(programHandle, 1, "a_Color");
            
            GLES20.glLinkProgram(programHandle);
            
            final int[] linkStatus = new int[1];
            GLES20.glGetProgramiv(programHandle, GLES20.GL_LINK_STATUS, linkStatus, 0);
            
            if(linkStatus[0] == 0)
            {
                GLES20.glDeleteProgram(programHandle);
                programHandle = 0;
            }
        }
        
        if(programHandle == 0)
        {
            throw new RuntimeException("failed to create program");
        }
        
        mMVPMatrixHandle = GLES20.glGetUniformLocation(programHandle, "u_MVPMatrix");
        mPositionHandle = GLES20.glGetAttribLocation(programHandle, "a_Position");
        mColorHandle = GLES20.glGetAttribLocation(programHandle, "a_Color");
        
        GLES20.glUseProgram(programHandle);
    }

    
    
}

最后附上效果图：