opengles系列-绘制三角形

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1.创建render类

**
 * 绘制三角形
 * Created by hxk on 2018/10/10.
 */

public class TriangleRenderer implements GLSurfaceView.Renderer {
    private final Context context;
    private final FloatBuffer vertexData;
    private static final int POSITION_COMPONENT_COUNT = 2;
    private static final int BYTES_PER_FLOAT = 4;
    private int program;//存储链接程序的ID
    private static final String U_COLOR = "u_Color";
    private int uColorLocation;
    private static final String A_POSITION = "a_Position";
    private int aPositionLocation;

    public TriangleRenderer(Context context) {
        this.context = context;
        float[] triangleVertices = {
                0f, 0.5f,
                -0.5f, 0f,
                0.5f, 0
        };
        vertexData = ByteBuffer.allocateDirect(triangleVertices.length * BYTES_PER_FLOAT)
                .order(ByteOrder.nativeOrder())
                .asFloatBuffer();
        vertexData.put(triangleVertices);//本地内存缓冲区

    }

    @Override
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        //清屏  RGBA
        glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
        String vertexShaderSource = TextResourceReader.readTextFileFromResource(context, R.raw.simple_vertex_shader);
        String fragmentShaderSource = TextResourceReader.readTextFileFromResource(context, R.raw.simple_fragment_shader);
        int vertexShader = ShaderHelper.compileVertexShader(vertexShaderSource);
        int fragmentShader = ShaderHelper.compileFragmentShader(fragmentShaderSource);
        //链接着色器
        program = ShaderHelper.linkProgram(vertexShader, fragmentShader);
        //验证程序对于opengl是否有效  debug
        ShaderHelper.validateProgram(program);
        //告诉opengl绘制任何东西到屏幕上需要使用这里定义的程序
        glUseProgram(program);
        //获取uniform的位置，把位置存入uColorLocation中
        uColorLocation = glGetUniformLocation(program, U_COLOR);
        //获取属性位置
        aPositionLocation = glGetAttribLocation(program, A_POSITION);
        //关联属性与顶点数据数组的数组
        //vertextData是我们在本地内存中创建的一个缓冲区，存的是位置
        //确保缓冲区从头开始读数据，置0
        vertexData.position(0);
        //告诉opengl从缓冲区vertextData中取数据找到属性a_Position的数据
        glVertexAttribPointer(aPositionLocation, POSITION_COMPONENT_COUNT, GL_FLOAT, false, 0, vertexData);
        //使能顶点数组
        glEnableVertexAttribArray(aPositionLocation);
    }

    @Override
    public void onSurfaceChanged(GL10 gl, int width, int height) {

    }

    @Override
    public void onDrawFrame(GL10 gl) {
        glClear(GL_COLOR_BUFFER_BIT);
        //绘制桌子
        glUniform4f(uColorLocation, 1.0f, 1.0f, 1.0f, 1.0f);
        //画个三角形，每个三角形有三个顶点，2个三角形6个顶点
        glDrawArrays(GL_TRIANGLES, 0, 3);

    }
}

2.创建activity

public class TriangleActivity extends AppCompatActivity {

    private GLSurfaceView glSurfaceView;
    private boolean rendererSet = false;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        glSurfaceView = new GLSurfaceView(this);

        // Check if the system supports OpenGL ES 2.0.
        ActivityManager activityManager =
                (ActivityManager) getSystemService(Context.ACTIVITY_SERVICE);
        ConfigurationInfo configurationInfo = activityManager
                .getDeviceConfigurationInfo();
        // Even though the latest emulator supports OpenGL ES 2.0,
        // it has a bug where it doesn't set the reqGlEsVersion so
        // the above check doesn't work. The below will detect if the
        // app is running on an emulator, and assume that it supports
        // OpenGL ES 2.0.
        final boolean supportsEs2 =
                configurationInfo.reqGlEsVersion >= 0x20000
                        || (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ICE_CREAM_SANDWICH_MR1
                        && (Build.FINGERPRINT.startsWith("generic")
                        || Build.FINGERPRINT.startsWith("unknown")
                        || Build.MODEL.contains("google_sdk")
                        || Build.MODEL.contains("Emulator")
                        || Build.MODEL.contains("Android SDK built for x86")));

        if (supportsEs2) {
            // Request an OpenGL ES 2.0 compatible context.
            glSurfaceView.setEGLContextClientVersion(2);

            // Assign our renderer.
            glSurfaceView.setRenderer(new TriangleRenderer(this));
            rendererSet = true;
        } else {
            /*
             * This is where you could create an OpenGL ES 1.x compatible
             * renderer if you wanted to support both ES 1 and ES 2. Since
             * we're not doing anything, the app will crash if the device
             * doesn't support OpenGL ES 2.0. If we publish on the market, we
             * should also add the following to AndroidManifest.xml:
             *
             * <uses-feature android:glEsVersion="0x00020000"
             * android:required="true" />
             *
             * This hides our app from those devices which don't support OpenGL
             * ES 2.0.
             */
            Toast.makeText(this, "This device does not support OpenGL ES 2.0.",
                    Toast.LENGTH_LONG).show();
            return;
        }

        setContentView(glSurfaceView);
    }

    @Override
    protected void onPause() {
        super.onPause();

        if (rendererSet) {
            glSurfaceView.onPause();
        }
    }

    @Override
    protected void onResume() {
        super.onResume();

        if (rendererSet) {
            glSurfaceView.onResume();
        }
    }
}

3.显示效果