Android中的OpenGL使用配置详解

<uses-feature android:glEsVersion="0x00020000" android:required="true" />

private class SimpleEGLConfigChooser extends ComponentSizeChooser {
    public SimpleEGLConfigChooser(boolean withDepthBuffer) {
        super(8, 8, 8, 0, withDepthBuffer ? 16 : 0, 0);
    }
}

// 设置默认EGLConfig的深度缓冲，true则为16位的深度缓冲
setEGLConfigChooser(boolean needDepth)
// 指定自定义的EGLConfigChooser
setEGLConfigChooser(android.opengl.GLSurfaceView.EGLConfigChooser configChooser)
// 指定各个分量的值
public void setEGLConfigChooser(int redSize, int greenSize, int blueSize,
            int alphaSize, int depthSize, int stencilSize)

// 设置渲染器
public void setRenderer(Renderer renderer)
// 设置渲染模式，仅在setRenderer之后调用生效
public void setRenderMode(int renderMode)

// DEBUG_CHECK_GL_ERROR：每次GL调用都会检查，如果出现glError则会抛出异常
// DEBUG_LOG_GL_CALLS：以TAG为GLSurfaceView将日志记录在verbose级别的日志中
setDebugFlags(int debugFlags)
// 用于调试跟踪代码，可自定义GLWrapper包装GL接口并返回GL接口，可在
setGLWrapper(android.opengl.GLSurfaceView.GLWrapper glWrapper)

// 给GLSurfaceView设置渲染器对象Renderer
public void setRenderer(Renderer renderer)
// 设置渲染模式，仅在setRenderer之后调用生效
public void setRenderMode(int renderMode)

public class GLES20Renderer implements Renderer {
    private static final String TAG = GLES20Renderer.class.getSimpleName();
    public void onSurfaceCreated(GL10 gl, EGLConfig config) {
        Log.i(TAG, "onSurfaceCreated");
        GLES20.glClearColor(0.0f, 0.0f, 1.0f, 1);
    }
    public void onSurfaceChanged(GL10 gl, int width, int height) {
        Log.i(TAG, "onSurfaceChanged");
        GLES20.glViewport(0, 0, width, height);
    }
    public void onDrawFrame(GL10 gl) {
        Log.i(TAG, "onDrawFrame");
        GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT | GLES20.GL_DEPTH_BUFFER_BIT);
    }
}

// Triangle
class Triangle(context: Context) {
    companion object {
        // 坐标数组中每个顶点的坐标数
        private const val COORDINATE_PER_VERTEX = 3
    }
    private var programHandle: Int = 0
    private var positionHandle: Int = 0
    private var colorHandler: Int = 0
    private var vPMatrixHandle: Int = 0
    private var vertexStride = COORDINATE_PER_VERTEX * 4
    // 三角形的三条边
    private var triangleCoordinate = floatArrayOf(     // 逆时针的顺序的三条边
        0.0f, 0.5f, 0.0f,      // top
        -0.5f, -0.5f, 0.0f,    // bottom left
        0.5f, -0.5f, 0.0f      // bottom right
    )
    // 颜色数组
    private val color = floatArrayOf(0.63671875f, 0.76953125f, 0.22265625f, 1.0f)
    private var vertexBuffer: FloatBuffer =
        // (number of coordinate values * 4 bytes per float)
        ByteBuffer.allocateDirect(triangleCoordinate.size * 4).run {
            // ByteBuffer使用本机字节序
            this.order(ByteOrder.nativeOrder())
            // ByteBuffer to FloatBuffer
            this.asFloatBuffer().apply {
                put(triangleCoordinate)
                position(0)
            }
        }
    init {
        // read shader sourceCode
        val vertexShaderCode = GLUtil.readShaderSourceCodeFromRaw(context, R.raw.vertex_shader_triangle_default)
        val fragmentShaderCode =
            GLUtil.readShaderSourceCodeFromRaw(context, R.raw.fragment_shader_triangle)
        if (vertexShaderCode.isNullOrEmpty() || fragmentShaderCode.isNullOrEmpty()) {
            throw RuntimeException("vertexShaderCode or fragmentShaderCode is null or empty")
        }
        // compile shader
        val vertexShaderHandler = GLUtil.compileShader(GLES20.GL_VERTEX_SHADER, vertexShaderCode)
        val fragmentShaderHandler =
            GLUtil.compileShader(GLES20.GL_FRAGMENT_SHADER, fragmentShaderCode)
        // create and link program
        programHandle = GLUtil.createAndLinkProgram(vertexShaderHandler, fragmentShaderHandler)
    }
    /**
 	 *  绘制方法
 	 */
    fun draw(mvpMatrix: FloatArray) {
        GLES20.glUseProgram(programHandle)
        // 获取attribute变量的地址索引
        // get handle to vertex shader's vPosition member
        positionHandle = GLES20.glGetAttribLocation(programHandle, "vPosition").also {
            // enable vertex attribute，默认是disable
            GLES20.glEnableVertexAttribArray(it)
            GLES20.glVertexAttribPointer(
                it, // 着色器中第一个顶点属性的位置
                COORDINATE_PER_VERTEX,
                GLES20.GL_FLOAT,
                false,
                vertexStride, // 连续的顶点属性组之间的间隔
                vertexBuffer
            )
        }
        // get handle to fragment shader's vColor member
        colorHandler = GLES20.glGetUniformLocation(programHandle, "vColor").also {
            GLES20.glUniform4fv(it, 1, color, 0)
        }
        // draw triangle
        GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, triangleCoordinate.size / COORDINATE_PER_VERTEX)
        GLES20.glDisableVertexAttribArray(positionHandle)
    }
}

// 渲染器实现
class MRenderer(private var context: Context) : GLSurfaceView.Renderer {
    private val tag = MRenderer::class.java.simpleName
    private lateinit var triangle: Triangle
    private val vPMatrix = FloatArray(16) // 模型视图投影矩阵
    private val projectionMatrix = FloatArray(16)
    private val viewMatrix = FloatArray(16)
    override fun onSurfaceCreated(gl: GL10?, config: EGLConfig?) {
        // 创建Surface时调用，在渲染开始时调用，用来创建渲染开始时需要的资源
        Log.d(tag, "onSurfaceCreated")
        triangle = Triangle(context)
    }
    override fun onSurfaceChanged(gl: GL10?, width: Int, height: Int) {
        // Surface改变大小时调用，设置视口
        Log.d(tag, "onSurfaceChanged")
        GLES20.glViewport(0, 0, width, height)
    }
    override fun onDrawFrame(gl: GL10?) {
        // 绘制当前frame，用于渲染处理具体的内容
        Log.d(tag, "onDrawFrame")
        triangle.draw(vPMatrix)
    }
}