OpenGLES2.0-绘制一个三角形

一:了解OpenGLES2.0

https://blog.csdn.net/junzia/article/details/52793354

二:绘制一个三角形

效果图

准备:清单文件设置

使用版本OpenGL ES2.0支持Android 2.2(API 8)和更高的版本

public MyView(Context context, AttributeSet attrs) {
    super(context, attrs);
    //设置版本
    setEGLContextClientVersion(2);
    setRenderer(this);
    //设置手动刷新
    setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);
}

第一步:顶点着色器片元着色器

//顶点着色器
private String vertexShaderCode = "attribute vec4 vPosition;" +
        " void main(){" +
        " gl_Position=vPosition;" +
        "}";
//片元着色器
private String fragmentShaderCode = "precision mediump float;" +
        " uniform vec4 vColor;" +
        " void main(){" +
        "gl_FragColor=vColor;" +
        "}";

第二步:绘制的图形的顶点坐标和颜色

float triangleCoords[] = {
        0.5f,  0.5f, 0.0f, // top
        -0.5f, -0.5f, 0.0f, // bottom left
        0.5f, -0.5f, 0.0f  // bottom right
};
float color[] = { 1.0f, 1.0f, 1.0f, 1.0f }; //白色

第三步:创建program对象，连接顶点和片元着色器，链接program对象

public class MyView extends GLSurfaceView implements GLSurfaceView.Renderer
返回三个方法
onSurfaceCreated、onSurfaceChanged和onDrawFrame

//创建program对象，连接顶点和片元着色器，链接program对象
@Override
public void onSurfaceCreated(GL10 gl, EGLConfig config) {
    //背景设置为灰色
    GLES20.glClearColor(0.5f,0.5f,0.5f,1.0f);
    //申请底层空间
    ByteBuffer bb = ByteBuffer.allocateDirect(
            triangleCoords.length * 4);
    bb.order(ByteOrder.nativeOrder());
    //将坐标数据转换为FloatBuffer,用以传入给OpenGL ES程序
    vertexBuffer = bb.asFloatBuffer();
    vertexBuffer.put(triangleCoords);
    vertexBuffer.position(0);
    int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER,
            vertexShaderCode);
    int fragmentShader = loadShader(GLES20.GL_FRAGMENT_SHADER,
            fragmentShaderCode);
    //创建一个空的OpenGLES程序
    mProgram = GLES20.glCreateProgram();
    //将顶点着色器加入到程序
    GLES20.glAttachShader(mProgram,vertexShader);
    //将片元着色器加入到程序中
    GLES20.glAttachShader(mProgram,fragmentShader);
    //链接到着色器程序
    GLES20.glLinkProgram(mProgram);
}

public static int loadShader(int shaderType,String source){
    int shader= GLES20.glCreateShader(shaderType);
    if(0!=shader){
        GLES20.glShaderSource(shader,source);
        GLES20.glCompileShader(shader);
        int[] compiled=new int[1];
        GLES20.glGetShaderiv(shader, GLES20.GL_COMPILE_STATUS,compiled,0);
        if(compiled[0]==0){
            Log.e("TAG","Could not compile shader:"+shaderType);
            Log.e("TAG","GLES20 Error:"+ GLES20.glGetShaderInfoLog(shader));
            GLES20.glDeleteShader(shader);
            shader=0;
        }
    }
    return shader;
}

第四步:在onSurfaceChanged中设置设置视图窗口

@Override
public void onSurfaceChanged(GL10 gl, int width, int height) {
    GLES20.glViewport(0,0,width,height);
}

第五步:在OnDrawFrame中绘制

@Override
public void onDrawFrame(GL10 gl) {
    //程序加入到OpenGLES2.0环境
    GLES20.glUseProgram(mProgram);
    //获取顶点着色器的vPosition成员句柄
    mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
    //启用三角形顶点的句柄
    GLES20.glEnableVertexAttribArray(mPositionHandle);
    //准备三角形的坐标数据
    GLES20.glVertexAttribPointer(mPositionHandle, 3,
            GLES20.GL_FLOAT, false,
            3*4, vertexBuffer);
    //获取片元着色器的vColor成员的句柄
    mColorHandle = GLES20.glGetUniformLocation(mProgram,"vColor");
    //设置绘制三角形的颜色
    GLES20.glUniform4fv(mColorHandle,1,color,0);
    //绘制三角形
    GLES20.glDrawArrays(GLES20.GL_TRIANGLES,0,3);
    //禁止顶点数组的句柄
    GLES20.glDisableVertexAttribArray(mPositionHandle);
}