创建着色器

 private final String vertexShaderCode =
      "attribute vec4 vPosition;" +
      "void main() {" +
      "  gl_Position = vPosition;" +
      "}";

private final String fragmentShaderCode =
      "precision mediump float;" +
      "uniform vec4 vColor;" +
      "void main() {" +
      "  gl_FragColor = vColor;" +
      "}";

这个很简单的，将传递进来的顶点属性直接给内置变量。片段着色器直接将传递的值给内置变量gl_FragColor，这个值会通过后续步骤之后显示在屏幕上的。

加载和编译

创建着色器

//根据type创建顶点着色器或者片元着色器
int shader = GLES20.glCreateShader(type);

加载程序

//将资源加入到着色器中，并编译
GLES20.glShaderSource(shader, shaderCode);

编译程序

GLES20.glCompileShader(shader);

检查异常

int []arr = new int[1]        GLES20.glGetShaderiv(shader,GLES20.GL_COMPILE_STATUS,arr,0);
       int i = arr[0];
       if (i == 0){
           //失败了
           int [] length = new int[1];
           GLES20.glGetShaderiv(shader,GLES20.GL_INFO_LOG_LENGTH,length,0);
           if (length[0]>0){
               String s = GLES20.glGetShaderInfoLog(shader);
               System.out.println(s);
           }
       }
       return shader;
   }

创建程序

创建程序

mProgram = GLES20.glCreateProgram();

附着着色器

GLES20.glAttachShader(mProgram,vertexShader);
GLES20.glAttachShader(mProgram,fragmentShader);

连接

GLES20.glLinkProgram(mProgram);

检查

int lin[] = new int[1];
GLES20.glGetProgramiv(mProgram,GLES20.GL_LINK_STATUS,lin,0);
if (lin[0] == 0){
    String s = GLES20.glGetProgramInfoLog(mProgram);
    System.out.println(s);
}

使用

GLES20.glUseProgram(mProgram);

得到位置

mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");

传值

color使用的是uniform，可以直接的传值,传入数组就可以了。

GLES20.glUniform4fv(mColorHandle, 1, color, 0);

但是对于属性值就比较麻烦一点，需要使用到FloatBuffer.它是一个特殊的区域，就是jvm和操作系统共享的区域。

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
    };


ByteBuffer bb = ByteBuffer.allocateDirect(triangleCoords.length * 4);
bb.order(ByteOrder.nativeOrder());
vertexBuffer = bb.asFloatBuffer();
vertexBuffer.put(triangleCoords);
vertexBuffer.position(0);

GLES20.glVertexAttribPointer(
        mPositionHandle,
        COORDS_PER_VERTEX,
        GLES20.GL_FLOAT,
        false,
        vertexStride,
        vertexBuffer);

完整代码

/**
 * 三角形
 */
public class Triangle extends BaseGameScreen {
   
    static final int COORDS_PER_VERTEX = 3;
    private FloatBuffer vertexBuffer;
    static 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
    };

    //顶点个数
    private final int vertexCount = triangleCoords.length / COORDS_PER_VERTEX;
    //顶点之间的偏移量
    private final int vertexStride = COORDS_PER_VERTEX * 4; // 每个顶点四个字节
    //设置颜色，依次为红绿蓝和透明通道
    float color[] = { 1.0f, 1.0f, 1.0f, 1.0f };
    private int mPositionHandle;
    private int mColorHandle;
    float d = 0.01F;
    public Triangle(){

    }

    public void create(){
        ByteBuffer bb = ByteBuffer.allocateDirect(
                triangleCoords.length * 4);
        bb.order(ByteOrder.nativeOrder());
        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);
        mProgram = GLES20.glCreateProgram();
        GLES20.glAttachShader(mProgram,vertexShader);
        GLES20.glAttachShader(mProgram,fragmentShader);
        GLES20.glLinkProgram(mProgram);
        //程序加入到环境里面
        GLES20.glUseProgram(mProgram);
//        检查是否有效
        GLES20.glValidateProgram(mProgram);
        //得到活跃的unifor
        int arr[] = new int[1];
        int arr1[] = new int[1];
        int arr2[] = new int[1];
        int arr3[] = new int[1];
        byte arr4[] = new byte[10];
        GLES20.glGetProgramiv(mProgram,GLES20.GL_ACTIVE_UNIFORMS,arr,0);
        GLES20.glGetActiveUniform(
                mProgram,
                1,
                1,
                arr1,
                1,
                arr2,
                1,
                arr3,
                1,
                arr4,
                0
                );
        mPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
        mColorHandle = GLES20.glGetUniformLocation(mProgram, "vColor");
    }

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

    @Override
    public void dispose() {

    }


    @Override
    public void render() {
        //获取位置句柄   属性句柄

        GLES20.glEnableVertexAttribArray(mPositionHandle);
        //准备三角形的坐标数据
        GLES20.glVertexAttribPointer(
                mPositionHandle,
                COORDS_PER_VERTEX,
                GLES20.GL_FLOAT,
                false,
                vertexStride,
                vertexBuffer);
        //获取片元着色器的vColor成员的句柄

        color[1] = color[1]-d;
        if (color[1]<=0||color[1]>=1){
            d=-d;
        }
        //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, vertexCount);
        //禁止顶点数组的句柄
        GLES20.glDisableVertexAttribArray(mPositionHandle);
    }
}