Android(安卓)为例编写一个 OpenGL ES 3.0 实例，Native & Java 两种实现

一、简介

通过这个 Sample，你将了解到 Android 中是怎么使用 OpenGL ES
通过绘制一个简单的静态三角形，来简单入门和了解它大致的流程（类似于 HelloWorld 工程）
介绍使用 Native 层 和 Java 层 两种方式来分别实现
本文暂不介绍具体的语法，但会给比较详细的注释和解释，帮助你理解
如果你还不了解 OpenGL ES 3.0 的渲染管线流程，建议你先了解一下。
传送门：OpenGL ES 3.0 渲染管线介绍

二、Native 实现

1. 头文件

由于我们使用的是 OpenGL ES 3.0，所以主要使用此头文件：

2. Activity

最终还是要显示在 Activity 上的，所以我们先准备这样一个 Activity，它直接使用 GLSurfaceView 作为 contentView。

public class SampleActivity extends AppCompatActivity {    private static final String TAG = "SampleActivity";    public static final String TYPE_NAME = "type";    public static final int TYPE_NATIVE = 0;    public static final int TYPE_JAVA = 1;    private GLSurfaceView mGlSurfaceView;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        if (!checkOpenGLES30()) {            Log.e(TAG, "con't support OpenGL ES 3.0!");            finish();        }        mGlSurfaceView = new GLSurfaceView(this);        mGlSurfaceView.setEGLContextClientVersion(3);        mGlSurfaceView.setRenderer(getRenderer());        mGlSurfaceView.setRenderMode(GLSurfaceView.RENDERMODE_WHEN_DIRTY);        setContentView(mGlSurfaceView);    }    private GLSurfaceView.Renderer getRenderer() {        Intent intent = getIntent();        int type = intent.getIntExtra(TYPE_NAME, TYPE_NATIVE);        Log.d(TAG, "type: " + type);        GLSurfaceView.Renderer renderer;        if (type == TYPE_NATIVE) {            renderer = new NativeRenderer(this);        } else {            renderer = new JavaRenderer(this);        }        return renderer;    }    private boolean checkOpenGLES30() {        ActivityManager am = (ActivityManager)getSystemService(Context.ACTIVITY_SERVICE);        ConfigurationInfo info = am.getDeviceConfigurationInfo();        return (info.reqGlEsVersion >= 0x30000);    }    @Override    protected void onPause() {        mGlSurfaceView.onPause();        super.onPause();    }    @Override    protected void onResume() {        mGlSurfaceView.onResume();        super.onResume();    }}

3. Renderer

我们先介绍 NativeRenderer 的实现，如下：

public class NativeRenderer implements GLSurfaceView.Renderer {    private Context mContext;    static {        System.loadLibrary("native-renderer");    }    public NativeRenderer(Context context) {        mContext = context;    }    @Override    public void onSurfaceCreated(GL10 gl, EGLConfig config) {        registerAssetManager(mContext.getAssets());        glInit();    }    @Override    public void onSurfaceChanged(GL10 gl, int width, int height) {        glResize(width, height);    }    @Override    public void onDrawFrame(GL10 gl) {        glDraw();    }    public native void registerAssetManager(AssetManager assetManager);    public native void glInit();    public native void glResize(int width, int height);    public native void glDraw();}

主要定义了4个 native 的方法，需要我们在 native 层实现。

4. ShaderUtils

说实现之前，我们先写一个工具类，负责加载和创建。工具类的作用就是可以重复使用的：

#include "ShaderUtils.h"#include #include "LogUtils.h"GLuint LoadShader(GLenum type, const char *shaderSource) {    // 1. create shader    GLuint shader = glCreateShader(type);    if (shader == GL_NONE) {        LOGE("create shader failed! type: %d", type);        return GL_NONE;    }    // 2. load shader source    glShaderSource(shader, 1, &shaderSource, NULL);    // 3. compile shared source    glCompileShader(shader);    // 4. check compile status    GLint compiled;    glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);    if (compiled == 0) { // compile failed        GLint len = 0;        glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &len);        if (len > 1) {            char *log = static_cast<char *>(malloc(sizeof(char) * len));            glGetShaderInfoLog(shader, len, NULL, log);            LOGE("Error compiling shader: %s", log);            free(log);        }        glDeleteShader(shader); // delete shader        return 0;    }    return shader;}GLuint CreateProgram(const char *vertexSource, const char *fragmentSource) {    // 1. load shader    GLuint vertexShader = LoadShader(GL_VERTEX_SHADER, vertexSource);    if (vertexShader == 0) {        LOGE("load vertex shader failed! ");        return 0;    }    GLuint fragmentShader = LoadShader(GL_FRAGMENT_SHADER, fragmentSource);    if (vertexShader == 0) {        LOGE("load fragment shader failed! ");        return 0;    }    // 2. create gl program    GLuint program = glCreateProgram();    if (program == 0) {        LOGE("create program failed! ");        return 0;    }    // 3. attach shader    glAttachShader(program, vertexShader);    glAttachShader(program, fragmentShader);    // we can delete shader after attach    glDeleteShader(vertexShader);    glDeleteShader(fragmentShader);    // 4. link program    glLinkProgram(program);    // 5. check link status    GLint linked;    glGetProgramiv(program, GL_LINK_STATUS, &linked);    if (linked == 0) { // link failed        GLint len = 0;        glGetProgramiv(program, GL_INFO_LOG_LENGTH, &len);        if (len > 1) {            char *log = static_cast<char *>(malloc(sizeof(char) * len));            glGetProgramInfoLog(program, len, NULL, log);            LOGE("Error link program: %s", log);            free(log);        }        glDeleteProgram(program); // delete program        return 0;    }    return program;}char *readAssetFile(const char *filename, AAssetManager *mgr) {    if (mgr == NULL) {        LOGE("pAssetManager is null!");        return NULL;    }    AAsset *pAsset = AAssetManager_open(mgr, filename, AASSET_MODE_UNKNOWN);    off_t len = AAsset_getLength(pAsset);    char *pBuffer = (char *) malloc(len + 1);    pBuffer[len] = '\0';    int numByte = AAsset_read(pAsset, pBuffer, len);    LOGD("numByte: %d, len: %d", numByte, len);    AAsset_close(pAsset);    return pBuffer;}

5. NativeRenderer.cpp

终于到了我们的渲染实现了，主要就是实现之前定义的那几个 native 方法：

#include "com_afei_openglsample_NativeRenderer.h"#include #include #include "LogUtils.h"#include "ShaderUtils.h"GLuint g_program;GLint g_position_handle;AAssetManager *g_pAssetManager = NULL;JNIEXPORT void JNICALL Java_com_afei_openglsample_NativeRenderer_glInit        (JNIEnv *env, jobject instance) {    char *vertexShaderSource = readAssetFile("vertex.vsh", g_pAssetManager);    char *fragmentShaderSource = readAssetFile("fragment.fsh", g_pAssetManager);    g_program = CreateProgram(vertexShaderSource, fragmentShaderSource);    if (g_program == GL_NONE) {        LOGE("gl init failed!");    }    // vPosition 是在 'vertex.vsh' 文件中定义的    GLint g_position_handle =glGetAttribLocation(g_program, "vPosition");    LOGD("g_position_handle: %d", g_position_handle);    glClearColor(0.0f, 0.0f, 0.0f, 1.0f); // 背景颜色设置为黑色 RGBA (range: 0.0 ~ 1.0)}JNIEXPORT void JNICALL Java_com_afei_openglsample_NativeRenderer_glResize        (JNIEnv *env, jobject instance, jint width, jint height) {    glViewport(0, 0, width, height); // 设置视距窗口}JNIEXPORT void JNICALL Java_com_afei_openglsample_NativeRenderer_glDraw        (JNIEnv *env, jobject instance) {    GLint vertexCount = 3;    // OpenGL的世界坐标系是 [-1, -1, 1, 1]    GLfloat vertices[] = {            0.0f, 0.5f, 0.0f, // 第一个点（x, y, z）            -0.5f, -0.5f, 0.0f, // 第二个点（x, y, z）            0.5f, -0.5f, 0.0f // 第三个点（x, y, z）    };    glClear(GL_COLOR_BUFFER_BIT); // clear color buffer    // 1. 选择使用的程序    glUseProgram(g_program);    // 2. 加载顶点数据    glVertexAttribPointer(g_position_handle, vertexCount, GL_FLOAT, GL_FALSE, 3 * 4, vertices);    glEnableVertexAttribArray(g_position_handle);    // 3. 绘制    glDrawArrays(GL_TRIANGLES, 0, vertexCount);}JNIEXPORT void JNICALL Java_com_afei_openglsample_NativeRenderer_registerAssetManager        (JNIEnv *env, jobject instance, jobject assetManager) {    if (assetManager) {        g_pAssetManager = AAssetManager_fromJava(env, assetManager);    } else {        LOGE("assetManager is null!")    }}

6. CMakeLists.txt

当然，它也是或不可少的，负责编译我们的 native 动态库。

cmake_minimum_required(VERSION 3.4.1)include_directories( ${CMAKE_SOURCE_DIR}/src/main/cpp/inc )add_library( native-renderer             SHARED             src/main/cpp/src/ShaderUtils.cpp             src/main/cpp/src/com_afei_openglsample_NativeRenderer.cpp )target_link_libraries( native-renderer                       # for 'AAssetManager_fromJava'                       android                       # for opengl es 3.0 library                       GLESv3                       # for log library                       log )

7. vertex.vsh 和 fragment.fsh

我们将顶点着色器和片元着色器的代码放在了 assets 目录下，实现分别为：

vertex.vsh

第一行是声明使用的版本，这里我们只是简单的将外面的输入，直接传给了 gl_Position

#version 300 eslayout(location = 0) in vec4 vPosition;void main() {    gl_Position = vPosition;}

fragment.fsh

同样第一行是声明使用的版本，然后绘制的颜色直接使用红色，即 RGBA (range: 0.0 ~ 1.0)

#version 300 esprecision mediump float;out vec4 fragColor;void main() {    fragColor = vec4 ( 1.0, 0.0, 0.0, 1.0 );}

8. 运行效果

三、Java 实现

1. Activity

和 Native 实现的代码一样，唯一的区别是使用 JavaRenderer 类作为渲染。

2. JavaRenderer

代码来看其实和 Native 层的极其类似，毕竟只是使用 Java 包了一层。

public class JavaRenderer implements GLSurfaceView.Renderer {    private static final String TAG = "JavaRenderer";    private Context mContext;    private int mProgram;    private int mPositionHandle;    public JavaRenderer(Context context) {        mContext = context;    }    @Override    public void onSurfaceCreated(GL10 gl, EGLConfig config) {        String vertexSource = ShaderUtils.loadFromAssets("vertex.vsh", mContext.getResources());        String fragmentSource = ShaderUtils.loadFromAssets("fragment.fsh", mContext.getResources());        mProgram = ShaderUtils.createProgram(vertexSource, fragmentSource);        // vPosition 是在 'vertex.vsh' 文件中定义的        mPositionHandle = GLES30.glGetAttribLocation(mProgram, "vPosition");        Log.d(TAG, "mPositionHandle: " + mPositionHandle);        // 背景颜色设置为黑色 RGBA (range: 0.0 ~ 1.0)        GLES30.glClearColor(0, 0, 0, 1);    }    @Override    public void onSurfaceChanged(GL10 gl, int width, int height) {        // 视距区域设置使用 GLSurfaceView 的宽高        GLES30.glViewport(0, 0, width, height);    }    @Override    public void onDrawFrame(GL10 gl) {        int vertexCount = 3;        // OpenGL的世界坐标系是 [-1, -1, 1, 1]        float[] vertices = new float[]{                0.0f, 0.5f, 0, // 第一个点（x, y, z）                -0.5f, -0.5f, 0, // 第二个点（x, y, z）                0.5f, -0.5f, 0 // 第三个点（x, y, z）        };        ByteBuffer vbb = ByteBuffer.allocateDirect(vertices.length * 4); // 一个 float 是四个字节        vbb.order(ByteOrder.nativeOrder()); // 必须要是 native order        FloatBuffer vertexBuffer = vbb.asFloatBuffer();        vertexBuffer.put(vertices);        vertexBuffer.position(0); // 这一行不要漏了        GLES30.glClear(GLES30.GL_COLOR_BUFFER_BIT); // clear color buffer        // 1. 选择使用的程序        GLES30.glUseProgram(mProgram);        // 2. 加载顶点数据        GLES30.glVertexAttribPointer(mPositionHandle, vertexCount, GLES30.GL_FLOAT, false, 3 * 4, vertexBuffer);        GLES30.glEnableVertexAttribArray(mPositionHandle);        // 3. 绘制        GLES30.glDrawArrays(GLES30.GL_TRIANGLES, 0, vertexCount);    }}

3. ShaderUtils

同样，我们将公共的方法抽离为一个工具类，并且，代码也是和 Native 层的极其类似。

public class ShaderUtils {    public static final String TAG = "ShaderUtils";    public static int loadShader(int type, String source) {        // 1. create shader        int shader = GLES30.glCreateShader(type);        if (shader == 0) {            Log.e(TAG, "create shared failed! type: " + type);            return 0;        }        // 2. load shader source        GLES30.glShaderSource(shader, source);        // 3. compile shared source        GLES30.glCompileShader(shader);        // 4. check compile status        int[] compiled = new int[1];        GLES30.glGetShaderiv(shader, GLES30.GL_COMPILE_STATUS, compiled, 0);        if (compiled[0] == 0) { // compile failed            Log.e(TAG, "Error compiling shader. type: " + type + ":");            Log.e(TAG, GLES30.glGetShaderInfoLog(shader));            GLES30.glDeleteShader(shader); // delete shader            return 0;        }        return shader;    }    public static int createProgram(String vertexSource, String fragmentSource) {        // 1. load shader        int vertexShader = loadShader(GLES30.GL_VERTEX_SHADER, vertexSource);        if (vertexShader == 0) {            Log.e(TAG, "load vertex shader failed! ");            return 0;        }        int fragmentShader = loadShader(GLES30.GL_FRAGMENT_SHADER, fragmentSource);        if (fragmentShader == 0) {            Log.e(TAG, "load fragment shader failed! ");            return 0;        }        // 2. create gl program        int program = GLES30.glCreateProgram();        if (program == 0) {            Log.e(TAG, "create program failed! ");            return 0;        }        // 3. attach shader        GLES30.glAttachShader(program, vertexShader);        GLES30.glAttachShader(program, fragmentShader);        // we can delete shader after attach        GLES30.glDeleteShader(vertexShader);        GLES30.glDeleteShader(fragmentShader);        // 4. link program        GLES30.glLinkProgram(program);        // 5. check link status        int[] linkStatus = new int[1];        GLES30.glGetProgramiv(program, GLES30.GL_LINK_STATUS, linkStatus, 0);        if (linkStatus[0] == 0) { // link failed            Log.e(TAG, "Error link program: ");            Log.e(TAG, GLES30.glGetProgramInfoLog(program));            GLES30.glDeleteProgram(program); // delete program            return 0;        }        return program;    }    public static String loadFromAssets(String fileName, Resources resources) {        String result = null;        try {            InputStream is = resources.getAssets().open(fileName);            int length = is.available();            byte[] data = new byte[length];            is.read(data);            is.close();            result = new String(data, "UTF-8");            result.replace("\\r\\n", "\\n");        } catch (IOException e) {            e.printStackTrace();        }        return result;    }}

4. vertex.vsh 和 fragment.fsh

同 Native 实现。

5. 运行效果

同 Native 运行效果。

四、总结

Native 实现方式和 Java 实现方式原理都是一样的，包括方法名都基本是一样的
部分未给出的代码，详细参见工程中的代码

五、完整工程地址

https://github.com/afei-cn/OpenGLSample