Android Graphics Tests 程序学习（2）： OpenGL EGL炫彩实例Native&Java

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注：文章都是通过阅读各位前辈总结的资料 Android 8.x && Linux（kernel 4.x）Qualcomm平台源码、加上自己的思考分析总结出来的，其中难免有理解不对的地方，欢迎大家批评指正。文章为个人学习、研究、欣赏之用，图文内容整理自互联网（◕‿◕），如有侵权，请联系删除，禁止转载（©Qualcomm ©Android @Linux 版权所有），谢谢。

首先感谢：

【EGL函数API文档】
【OpenGL ES EGL介绍】

正是由于前人的分析和总结，帮助我节约了大量的时间和精力，再次感谢！！！

Google Pixel、Pixel XL 内核代码（==文章基于 Kernel-4.x==）：
Kernel source for Pixel 2 (walleye) and Pixel 2 XL (taimen) - GitHub

AOSP 源码（==文章基于 Android 8.x==）：
Android 系统全套源代码分享 (更新到 8.1.0_r1)

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==源码（部分）==：

opengl

• android\frameworks\native\opengl\tests\gl2_basic\
• android\frameworks\native\opengl\tests\gl2_java\
• android\frameworks\native\opengl\tests\angeles\

---

(一)、gl2_basic

1.1、源码：

#include <stdlib.h>
#include <stdio.h>
#include <time.h>
#include <sched.h>
#include <sys/resource.h>

#include <EGL/egl.h>
#include <GLES2/gl2.h>
#include <GLES2/gl2ext.h>

#include <utils/Timers.h>

#include <WindowSurface.h>
#include <EGLUtils.h>

using namespace android;
extern "C" EGLAPI const char* eglQueryStringImplementationANDROID(EGLDisplay dpy, EGLint name);

static void printGLString(const char *name, GLenum s) {
    // fprintf(stderr, "printGLString %s, %d\n", name, s);
    const char *v = (const char *) glGetString(s);
    // int error = glGetError();
    // fprintf(stderr, "glGetError() = %d, result of glGetString = %x\n", error,
    //        (unsigned int) v);
    // if ((v < (const char*) 0) || (v > (const char*) 0x10000))
    //    fprintf(stderr, "GL %s = %s\n", name, v);
    // else
    //    fprintf(stderr, "GL %s = (null) 0x%08x\n", name, (unsigned int) v);
    fprintf(stderr, "GL %s = %s\n", name, v);
}

static void printEGLString(EGLDisplay dpy, const char *name, GLenum s) {
    const char *v = (const char *) eglQueryString(dpy, s);
    const char* va = (const char*)eglQueryStringImplementationANDROID(dpy, s);
    fprintf(stderr, "GL %s = %s\nImplementationANDROID: %s\n", name, v, va);
}

static void checkEglError(const char* op, EGLBoolean returnVal = EGL_TRUE) {
    if (returnVal != EGL_TRUE) {
        fprintf(stderr, "%s() returned %d\n", op, returnVal);
    }

    for (EGLint error = eglGetError(); error != EGL_SUCCESS; error
            = eglGetError()) {
        fprintf(stderr, "after %s() eglError %s (0x%x)\n", op, EGLUtils::strerror(error),
                error);
    }
}

static void checkGlError(const char* op) {
    for (GLint error = glGetError(); error; error
            = glGetError()) {
        fprintf(stderr, "after %s() glError (0x%x)\n", op, error);
    }
}

static const char gVertexShader[] = "attribute vec4 vPosition;\n"
    "void main() {\n"
    "  gl_Position = vPosition;\n"
    "}\n";

static const char gFragmentShader[] = "precision mediump float;\n"
    "void main() {\n"
    "  gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);\n"
    "}\n";

GLuint loadShader(GLenum shaderType, const char* pSource) {
    GLuint shader = glCreateShader(shaderType);
    if (shader) {
        glShaderSource(shader, 1, &pSource, NULL);
        glCompileShader(shader);
        GLint compiled = 0;
        glGetShaderiv(shader, GL_COMPILE_STATUS, &compiled);
        if (!compiled) {
            GLint infoLen = 0;
            glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &infoLen);
            if (infoLen) {
                char* buf = (char*) malloc(infoLen);
                if (buf) {
                    glGetShaderInfoLog(shader, infoLen, NULL, buf);
                    fprintf(stderr, "Could not compile shader %d:\n%s\n",
                            shaderType, buf);
                    free(buf);
                }
                glDeleteShader(shader);
                shader = 0;
            }
        }
    }
    return shader;
}

GLuint createProgram(const char* pVertexSource, const char* pFragmentSource) {
    GLuint vertexShader = loadShader(GL_VERTEX_SHADER, pVertexSource);
    if (!vertexShader) {
        return 0;
    }

    GLuint pixelShader = loadShader(GL_FRAGMENT_SHADER, pFragmentSource);
    if (!pixelShader) {
        return 0;
    }

    GLuint program = glCreateProgram();
    if (program) {
        glAttachShader(program, vertexShader);
        checkGlError("glAttachShader");
        glAttachShader(program, pixelShader);
        checkGlError("glAttachShader");
        glLinkProgram(program);
        GLint linkStatus = GL_FALSE;
        glGetProgramiv(program, GL_LINK_STATUS, &linkStatus);
        if (linkStatus != GL_TRUE) {
            GLint bufLength = 0;
            glGetProgramiv(program, GL_INFO_LOG_LENGTH, &bufLength);
            if (bufLength) {
                char* buf = (char*) malloc(bufLength);
                if (buf) {
                    glGetProgramInfoLog(program, bufLength, NULL, buf);
                    fprintf(stderr, "Could not link program:\n%s\n", buf);
                    free(buf);
                }
            }
            glDeleteProgram(program);
            program = 0;
        }
    }
    return program;
}

GLuint gProgram;
GLuint gvPositionHandle;

bool setupGraphics(int w, int h) {
    gProgram = createProgram(gVertexShader, gFragmentShader);
    if (!gProgram) {
        return false;
    }
    gvPositionHandle = glGetAttribLocation(gProgram, "vPosition");
    checkGlError("glGetAttribLocation");
    fprintf(stderr, "glGetAttribLocation(\"vPosition\") = %d\n",
            gvPositionHandle);

    glViewport(0, 0, w, h);
    checkGlError("glViewport");
    return true;
}

const GLfloat gTriangleVertices[] = { 0.0f, 0.5f, -0.5f, -0.5f,
        0.5f, -0.5f };

void renderFrame() {
    glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
    checkGlError("glClearColor");
    glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);
    checkGlError("glClear");

    glUseProgram(gProgram);
    checkGlError("glUseProgram");

    glVertexAttribPointer(gvPositionHandle, 2, GL_FLOAT, GL_FALSE, 0, gTriangleVertices);
    checkGlError("glVertexAttribPointer");
    glEnableVertexAttribArray(gvPositionHandle);
    checkGlError("glEnableVertexAttribArray");
    glDrawArrays(GL_TRIANGLES, 0, 3);
    checkGlError("glDrawArrays");
}

void printEGLConfiguration(EGLDisplay dpy, EGLConfig config) {

#define X(VAL) {VAL, #VAL}
    struct {EGLint attribute; const char* name;} names[] = {
    X(EGL_BUFFER_SIZE),
    X(EGL_ALPHA_SIZE),
    X(EGL_BLUE_SIZE),
    X(EGL_GREEN_SIZE),
    X(EGL_RED_SIZE),
    X(EGL_DEPTH_SIZE),
    X(EGL_STENCIL_SIZE),
    X(EGL_CONFIG_CAVEAT),
    X(EGL_CONFIG_ID),
    X(EGL_LEVEL),
    X(EGL_MAX_PBUFFER_HEIGHT),
    X(EGL_MAX_PBUFFER_PIXELS),
    X(EGL_MAX_PBUFFER_WIDTH),
    X(EGL_NATIVE_RENDERABLE),
    X(EGL_NATIVE_VISUAL_ID),
    X(EGL_NATIVE_VISUAL_TYPE),
    X(EGL_SAMPLES),
    X(EGL_SAMPLE_BUFFERS),
    X(EGL_SURFACE_TYPE),
    X(EGL_TRANSPARENT_TYPE),
    X(EGL_TRANSPARENT_RED_VALUE),
    X(EGL_TRANSPARENT_GREEN_VALUE),
    X(EGL_TRANSPARENT_BLUE_VALUE),
    X(EGL_BIND_TO_TEXTURE_RGB),
    X(EGL_BIND_TO_TEXTURE_RGBA),
    X(EGL_MIN_SWAP_INTERVAL),
    X(EGL_MAX_SWAP_INTERVAL),
    X(EGL_LUMINANCE_SIZE),
    X(EGL_ALPHA_MASK_SIZE),
    X(EGL_COLOR_BUFFER_TYPE),
    X(EGL_RENDERABLE_TYPE),
    X(EGL_CONFORMANT),
   };
#undef X

    for (size_t j = 0; j < sizeof(names) / sizeof(names[0]); j++) {
        EGLint value = -1;
        EGLint returnVal = eglGetConfigAttrib(dpy, config, names[j].attribute, &value);
        EGLint error = eglGetError();
        if (returnVal && error == EGL_SUCCESS) {
            printf(" %s: ", names[j].name);
            printf("%d (0x%x)", value, value);
        }
    }
    printf("\n");
}

int printEGLConfigurations(EGLDisplay dpy) {
    EGLint numConfig = 0;
    EGLint returnVal = eglGetConfigs(dpy, NULL, 0, &numConfig);
    checkEglError("eglGetConfigs", returnVal);
    if (!returnVal) {
        return false;
    }

    printf("Number of EGL configuration: %d\n", numConfig);

    EGLConfig* configs = (EGLConfig*) malloc(sizeof(EGLConfig) * numConfig);
    if (! configs) {
        printf("Could not allocate configs.\n");
        return false;
    }

    returnVal = eglGetConfigs(dpy, configs, numConfig, &numConfig);
    checkEglError("eglGetConfigs", returnVal);
    if (!returnVal) {
        free(configs);
        return false;
    }

    for(int i = 0; i < numConfig; i++) {
        printf("Configuration %d\n", i);
        printEGLConfiguration(dpy, configs[i]);
    }

    free(configs);
    return true;
}

int main(int /*argc*/, char** /*argv*/) {
    EGLBoolean returnValue;
    EGLConfig myConfig = {0};

    EGLint context_attribs[] = { EGL_CONTEXT_CLIENT_VERSION, 2, EGL_NONE };
    EGLint s_configAttribs[] = {
            EGL_SURFACE_TYPE, EGL_WINDOW_BIT,
            EGL_RENDERABLE_TYPE, EGL_OPENGL_ES2_BIT,
            EGL_NONE };
    EGLint majorVersion;
    EGLint minorVersion;
    EGLContext context;
    EGLSurface surface;
    EGLint w, h;

    EGLDisplay dpy;

    checkEglError("<init>");
    dpy = eglGetDisplay(EGL_DEFAULT_DISPLAY);
    checkEglError("eglGetDisplay");
    if (dpy == EGL_NO_DISPLAY) {
        printf("eglGetDisplay returned EGL_NO_DISPLAY.\n");
        return 0;
    }

    returnValue = eglInitialize(dpy, &majorVersion, &minorVersion);
    checkEglError("eglInitialize", returnValue);
    fprintf(stderr, "EGL version %d.%d\n", majorVersion, minorVersion);
    if (returnValue != EGL_TRUE) {
        printf("eglInitialize failed\n");
        return 0;
    }

    if (!printEGLConfigurations(dpy)) {
        printf("printEGLConfigurations failed\n");
        return 0;
    }

    checkEglError("printEGLConfigurations");

    WindowSurface windowSurface;
    EGLNativeWindowType window = windowSurface.getSurface();
    returnValue = EGLUtils::selectConfigForNativeWindow(dpy, s_configAttribs, window, &myConfig);
    if (returnValue) {
        printf("EGLUtils::selectConfigForNativeWindow() returned %d", returnValue);
        return 0;
    }

    checkEglError("EGLUtils::selectConfigForNativeWindow");

    printf("Chose this configuration:\n");
    printEGLConfiguration(dpy, myConfig);

    surface = eglCreateWindowSurface(dpy, myConfig, window, NULL);
    checkEglError("eglCreateWindowSurface");
    if (surface == EGL_NO_SURFACE) {
        printf("gelCreateWindowSurface failed.\n");
        return 0;
    }

    context = eglCreateContext(dpy, myConfig, EGL_NO_CONTEXT, context_attribs);
    checkEglError("eglCreateContext");
    if (context == EGL_NO_CONTEXT) {
        printf("eglCreateContext failed\n");
        return 0;
    }
    returnValue = eglMakeCurrent(dpy, surface, surface, context);
    checkEglError("eglMakeCurrent", returnValue);
    if (returnValue != EGL_TRUE) {
        return 0;
    }
    eglQuerySurface(dpy, surface, EGL_WIDTH, &w);
    checkEglError("eglQuerySurface");
    eglQuerySurface(dpy, surface, EGL_HEIGHT, &h);
    checkEglError("eglQuerySurface");
    GLint dim = w < h ? w : h;

    fprintf(stderr, "Window dimensions: %d x %d\n", w, h);

    printGLString("Version", GL_VERSION);
    printGLString("Vendor", GL_VENDOR);
    printGLString("Renderer", GL_RENDERER);
    printGLString("Extensions", GL_EXTENSIONS);
    printEGLString(dpy, "EGL Extensions", EGL_EXTENSIONS);

    if(!setupGraphics(w, h)) {
        fprintf(stderr, "Could not set up graphics.\n");
        return 0;
    }

    for (;;) {
        renderFrame();
        eglSwapBuffers(dpy, surface);
        checkEglError("eglSwapBuffers");
    }

    return 0;
}

(二)、gl2_java

2.1、源码1：

package com.android.gl2java;

import android.app.Activity;
import android.os.Bundle;
import android.util.Log;
import android.view.WindowManager;

import java.io.File;


public class GL2JavaActivity extends Activity {

    GL2JavaView mView;

    @Override protected void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        mView = new GL2JavaView(getApplication());
    setContentView(mView);
    }

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

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

2.2、源码2：

package com.android.gl2java;

import android.content.Context;
import android.opengl.GLSurfaceView;
import android.util.AttributeSet;
import android.util.Log;
import android.view.KeyEvent;
import android.view.MotionEvent;

import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.FloatBuffer;

import javax.microedition.khronos.egl.EGL10;
import javax.microedition.khronos.egl.EGLConfig;
import javax.microedition.khronos.egl.EGLContext;
import javax.microedition.khronos.egl.EGLDisplay;
import javax.microedition.khronos.opengles.GL10;

import android.opengl.GLES20;

/**
 * An implementation of SurfaceView that uses the dedicated surface for
 * displaying an OpenGL animation.  This allows the animation to run in a
 * separate thread, without requiring that it be driven by the update mechanism
 * of the view hierarchy.
 *
 * The application-specific rendering code is delegated to a GLView.Renderer
 * instance.
 */
class GL2JavaView extends GLSurfaceView {
    private static String TAG = "GL2JavaView";

    public GL2JavaView(Context context) {
        super(context);
        setEGLContextClientVersion(2);
        setRenderer(new Renderer());
    }

    private static class Renderer implements GLSurfaceView.Renderer {

        public Renderer() {
            mTriangleVertices = ByteBuffer.allocateDirect(mTriangleVerticesData.length * 4)
                .order(ByteOrder.nativeOrder()).asFloatBuffer();
            mTriangleVertices.put(mTriangleVerticesData).position(0);
        }

        public void onDrawFrame(GL10 gl) {
            GLES20.glClearColor(0.0f, 0.0f, 1.0f, 1.0f);
            GLES20.glClear( GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);
            GLES20.glUseProgram(mProgram);
            checkGlError("glUseProgram");

            GLES20.glVertexAttribPointer(mvPositionHandle, 2, GLES20.GL_FLOAT, false, 0, mTriangleVertices);
            checkGlError("glVertexAttribPointer");
            GLES20.glEnableVertexAttribArray(mvPositionHandle);
            checkGlError("glEnableVertexAttribArray");
            GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3);
            checkGlError("glDrawArrays");

        }

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

        public void onSurfaceCreated(GL10 gl, EGLConfig config) {
            mProgram = createProgram(mVertexShader, mFragmentShader);
            if (mProgram == 0) {
                return;
            }
            mvPositionHandle = GLES20.glGetAttribLocation(mProgram, "vPosition");
            checkGlError("glGetAttribLocation");
            if (mvPositionHandle == -1) {
                throw new RuntimeException("Could not get attrib location for vPosition");
            }
        }

        private int loadShader(int shaderType, String source) {
            int shader = GLES20.glCreateShader(shaderType);
            if (shader != 0) {
                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.glGetShaderInfoLog(shader));
                    GLES20.glDeleteShader(shader);
                    shader = 0;
                }
            }
            return shader;
        }

        private int createProgram(String vertexSource, String fragmentSource) {
            int vertexShader = loadShader(GLES20.GL_VERTEX_SHADER, vertexSource);
            if (vertexShader == 0) {
                return 0;
            }

            int pixelShader = loadShader(GLES20.GL_FRAGMENT_SHADER, fragmentSource);
            if (pixelShader == 0) {
                return 0;
            }

            int program = GLES20.glCreateProgram();
            if (program != 0) {
                GLES20.glAttachShader(program, vertexShader);
                checkGlError("glAttachShader");
                GLES20.glAttachShader(program, pixelShader);
                checkGlError("glAttachShader");
                GLES20.glLinkProgram(program);
                int[] linkStatus = new int[1];
                GLES20.glGetProgramiv(program, GLES20.GL_LINK_STATUS, linkStatus, 0);
                if (linkStatus[0] != GLES20.GL_TRUE) {
                    Log.e(TAG, "Could not link program: ");
                    Log.e(TAG, GLES20.glGetProgramInfoLog(program));
                    GLES20.glDeleteProgram(program);
                    program = 0;
                }
            }
            return program;
        }

        private void checkGlError(String op) {
            int error;
            while ((error = GLES20.glGetError()) != GLES20.GL_NO_ERROR) {
                Log.e(TAG, op + ": glError " + error);
                throw new RuntimeException(op + ": glError " + error);
            }
        }

        private final float[] mTriangleVerticesData = { 0.0f, 0.5f, -0.5f, -0.5f,
                0.5f, -0.5f };

        private FloatBuffer mTriangleVertices;

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

        private final String mFragmentShader = "precision mediump float;\n"
            + "void main() {\n"
            + "  gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);\n"
            + "}\n";

        private int mProgram;
        private int mvPositionHandle;

    }
}

这个和前面例子1的界面效果是一摸一样的。

(三)、angeles

首先看看效果图，可以看到丰富的多彩世界的模型啦~

3.1、源码1：

\android\frameworks\native\opengl\tests\angeles\app-linux.cpp

#include <stdlib.h>
#include <stdio.h>
#include <sys/time.h>

#include <EGL/egl.h>
#include <GLES/gl.h>

#include <EGLUtils.h>
#include <WindowSurface.h>

using namespace android;

#include "app.h"


int gAppAlive = 1;

static const char sAppName[] =
        "San Angeles Observation OpenGL ES version example (Linux)";

static int sWindowWidth = WINDOW_DEFAULT_WIDTH;
static int sWindowHeight = WINDOW_DEFAULT_HEIGHT;
static EGLDisplay sEglDisplay = EGL_NO_DISPLAY;
static EGLContext sEglContext = EGL_NO_CONTEXT;
static EGLSurface sEglSurface = EGL_NO_SURFACE;

const char *egl_strerror(unsigned err)
{
    switch(err){
        case EGL_SUCCESS: return "SUCCESS";
        case EGL_NOT_INITIALIZED: return "NOT INITIALIZED";
        case EGL_BAD_ACCESS: return "BAD ACCESS";
        case EGL_BAD_ALLOC: return "BAD ALLOC";
        case EGL_BAD_ATTRIBUTE: return "BAD_ATTRIBUTE";
        case EGL_BAD_CONFIG: return "BAD CONFIG";
        case EGL_BAD_CONTEXT: return "BAD CONTEXT";
        case EGL_BAD_CURRENT_SURFACE: return "BAD CURRENT SURFACE";
        case EGL_BAD_DISPLAY: return "BAD DISPLAY";
        case EGL_BAD_MATCH: return "BAD MATCH";
        case EGL_BAD_NATIVE_PIXMAP: return "BAD NATIVE PIXMAP";
        case EGL_BAD_NATIVE_WINDOW: return "BAD NATIVE WINDOW";
        case EGL_BAD_PARAMETER: return "BAD PARAMETER";
        case EGL_BAD_SURFACE: return "BAD_SURFACE";
        //    case EGL_CONTEXT_LOST: return "CONTEXT LOST";
        default: return "UNKNOWN";
    }
}

void egl_error(const char *name)
{
    unsigned err = eglGetError();
    if(err != EGL_SUCCESS) {
        fprintf(stderr,"%s(): egl error 0x%x (%s)\n", 
                name, err, egl_strerror(err));
    }
}

static void checkGLErrors()
{
    GLenum error = glGetError();
    if (error != GL_NO_ERROR)
        fprintf(stderr, "GL Error: 0x%04x\n", (int)error);
}


static void checkEGLErrors()
{
    EGLint error = eglGetError();
    // GLESonGL seems to be returning 0 when there is no errors?
    if (error && error != EGL_SUCCESS)
        fprintf(stderr, "EGL Error: 0x%04x\n", (int)error);
}

static int initGraphics(EGLint samples, const WindowSurface& windowSurface)
{
    EGLint configAttribs[] = {
            EGL_DEPTH_SIZE, 16,
            EGL_SAMPLE_BUFFERS, samples ? 1 : 0,
                    EGL_SAMPLES, samples,
                    EGL_NONE
    };

    EGLint majorVersion;
    EGLint minorVersion;
    EGLContext context;
    EGLConfig config;
    EGLSurface surface;
    EGLint w, h;
    EGLDisplay dpy;

    EGLNativeWindowType window = windowSurface.getSurface();

    dpy = eglGetDisplay(EGL_DEFAULT_DISPLAY);
    eglInitialize(dpy, &majorVersion, &minorVersion);

    status_t err = EGLUtils::selectConfigForNativeWindow(
            dpy, configAttribs, window, &config);
    if (err) {
        fprintf(stderr, "couldn't find an EGLConfig matching the screen format\n");
        return 0;
    }

    surface = eglCreateWindowSurface(dpy, config, window, NULL);
    egl_error("eglCreateWindowSurface");

    fprintf(stderr,"surface = %p\n", surface);

    context = eglCreateContext(dpy, config, NULL, NULL);
    egl_error("eglCreateContext");
    fprintf(stderr,"context = %p\n", context);

    eglMakeCurrent(dpy, surface, surface, context);
    egl_error("eglMakeCurrent");

    eglQuerySurface(dpy, surface, EGL_WIDTH, &sWindowWidth);
    eglQuerySurface(dpy, surface, EGL_HEIGHT, &sWindowHeight);

    sEglDisplay = dpy;
    sEglSurface = surface;
    sEglContext = context;

    if (samples == 0) {
        // GL_MULTISAMPLE is enabled by default
        glDisable(GL_MULTISAMPLE);
    }

    return EGL_TRUE;
}


static void deinitGraphics()
{
    eglMakeCurrent(sEglDisplay, NULL, NULL, NULL);
    eglDestroyContext(sEglDisplay, sEglContext);
    eglDestroySurface(sEglDisplay, sEglSurface);
    eglTerminate(sEglDisplay);
}


int main(int argc, char *argv[])
{
    unsigned samples = 0;
    printf("usage: %s [samples]\n", argv[0]);
    if (argc == 2) {
        samples = atoi( argv[1] );
        printf("Multisample enabled: GL_SAMPLES = %u\n", samples);
    }

    WindowSurface windowSurface;
    if (!initGraphics(samples, windowSurface))
    {
        fprintf(stderr, "Graphics initialization failed.\n");
        return EXIT_FAILURE;
    }

    appInit();

    struct timeval timeTemp;
    int frameCount = 0;
    gettimeofday(&timeTemp, NULL);
    double totalTime = timeTemp.tv_usec/1000000.0 + timeTemp.tv_sec;

    while (gAppAlive)
    {
        struct timeval timeNow;

        gettimeofday(&timeNow, NULL);
        appRender(timeNow.tv_sec * 1000 + timeNow.tv_usec / 1000,
                sWindowWidth, sWindowHeight);
        checkGLErrors();
        eglSwapBuffers(sEglDisplay, sEglSurface);
        checkEGLErrors();
        frameCount++;
    }

    gettimeofday(&timeTemp, NULL);

    appDeinit();
    deinitGraphics();

    totalTime = (timeTemp.tv_usec/1000000.0 + timeTemp.tv_sec) - totalTime;
    printf("totalTime=%f s, frameCount=%d, %.2f fps\n",
            totalTime, frameCount, frameCount/totalTime);

    return EXIT_SUCCESS;
}

3.2、源码2：

\android\frameworks\native\opengl\tests\angeles\demo.c

#include <stdlib.h>
#include <math.h>
#include <float.h>
#include <assert.h>

#include <GLES/gl.h>

#include "app.h"
#include "shapes.h"
#include "cams.h"


// Total run length is 20 * camera track base unit length (see cams.h).
#define RUN_LENGTH  (20 * CAMTRACK_LEN)
#undef PI
#define PI 3.1415926535897932f
#define RANDOM_UINT_MAX 65535


static unsigned long sRandomSeed = 0;

static void seedRandom(unsigned long seed)
{
    sRandomSeed = seed;
}

static unsigned long randomUInt()
{
    sRandomSeed = sRandomSeed * 0x343fd + 0x269ec3;
    return sRandomSeed >> 16;
}


// Capped conversion from float to fixed.
static long floatToFixed(float value)
{
    if (value < -32768) value = -32768;
    if (value > 32767) value = 32767;
    return (long)(value * 65536);
}

#define FIXED(value) floatToFixed(value)


// Definition of one GL object in this demo.
typedef struct {
    /* Vertex array and color array are enabled for all objects, so their
     * pointers must always be valid and non-NULL. Normal array is not
     * used by the ground plane, so when its pointer is NULL then normal
     * array usage is disabled.
     *
     * Vertex array is supposed to use GL_FIXED datatype and stride 0
     * (i.e. tightly packed array). Color array is supposed to have 4
     * components per color with GL_UNSIGNED_BYTE datatype and stride 0.
     * Normal array is supposed to use GL_FIXED datatype and stride 0.
     */
    GLfixed *vertexArray;
    GLubyte *colorArray;
    GLfixed *normalArray;
    GLint vertexComponents;
    GLsizei count;
} GLOBJECT;


static long sStartTick = 0;
static long sTick = 0;

static int sCurrentCamTrack = 0;
static long sCurrentCamTrackStartTick = 0;
static long sNextCamTrackStartTick = 0x7fffffff;

static GLOBJECT *sSuperShapeObjects[SUPERSHAPE_COUNT] = { NULL };
static GLOBJECT *sGroundPlane = NULL;


typedef struct {
    float x, y, z;
} VECTOR3;


static void freeGLObject(GLOBJECT *object)
{
    if (object == NULL)
        return;
    free(object->normalArray);
    free(object->colorArray);
    free(object->vertexArray);
    free(object);
}


static GLOBJECT * newGLObject(long vertices, int vertexComponents,
                              int useNormalArray)
{
    GLOBJECT *result;
    result = (GLOBJECT *)malloc(sizeof(GLOBJECT));
    if (result == NULL)
        return NULL;
    result->count = vertices;
    result->vertexComponents = vertexComponents;
    result->vertexArray = (GLfixed *)malloc(vertices * vertexComponents *
                                            sizeof(GLfixed));
    result->colorArray = (GLubyte *)malloc(vertices * 4 * sizeof(GLubyte));
    if (useNormalArray)
    {
        result->normalArray = (GLfixed *)malloc(vertices * 3 *
                                                sizeof(GLfixed));
    }
    else
        result->normalArray = NULL;
    if (result->vertexArray == NULL ||
        result->colorArray == NULL ||
        (useNormalArray && result->normalArray == NULL))
    {
        freeGLObject(result);
        return NULL;
    }
    return result;
}


static void drawGLObject(GLOBJECT *object)
{
    assert(object != NULL);

    glVertexPointer(object->vertexComponents, GL_FIXED,
                    0, object->vertexArray);
    glColorPointer(4, GL_UNSIGNED_BYTE, 0, object->colorArray);

    // Already done in initialization:
    //glEnableClientState(GL_VERTEX_ARRAY);
    //glEnableClientState(GL_COLOR_ARRAY);

    if (object->normalArray)
    {
        glNormalPointer(GL_FIXED, 0, object->normalArray);
        glEnableClientState(GL_NORMAL_ARRAY);
    }
    else
        glDisableClientState(GL_NORMAL_ARRAY);
    glDrawArrays(GL_TRIANGLES, 0, object->count);
}


static void vector3Sub(VECTOR3 *dest, VECTOR3 *v1, VECTOR3 *v2)
{
    dest->x = v1->x - v2->x;
    dest->y = v1->y - v2->y;
    dest->z = v1->z - v2->z;
}


static void superShapeMap(VECTOR3 *point, float r1, float r2, float t, float p)
{
    // sphere-mapping of supershape parameters
    point->x = (float)(cos(t) * cos(p) / r1 / r2);
    point->y = (float)(sin(t) * cos(p) / r1 / r2);
    point->z = (float)(sin(p) / r2);
}


static float ssFunc(const float t, const float *p)
{
    return (float)(pow(pow(fabs(cos(p[0] * t / 4)) / p[1], p[4]) +
                       pow(fabs(sin(p[0] * t / 4)) / p[2], p[5]), 1 / p[3]));
}


// Creates and returns a supershape object.
// Based on Paul Bourke's POV-Ray implementation.
// http://astronomy.swin.edu.au/~pbourke/povray/supershape/
static GLOBJECT * createSuperShape(const float *params)
{
    const int resol1 = (int)params[SUPERSHAPE_PARAMS - 3];
    const int resol2 = (int)params[SUPERSHAPE_PARAMS - 2];
    // latitude 0 to pi/2 for no mirrored bottom
    // (latitudeBegin==0 for -pi/2 to pi/2 originally)
    const int latitudeBegin = resol2 / 4;
    const int latitudeEnd = resol2 / 2;    // non-inclusive
    const int longitudeCount = resol1;
    const int latitudeCount = latitudeEnd - latitudeBegin;
    const long triangleCount = longitudeCount * latitudeCount * 2;
    const long vertices = triangleCount * 3;
    GLOBJECT *result;
    float baseColor[3];
    int a, longitude, latitude;
    long currentVertex, currentQuad;

    result = newGLObject(vertices, 3, 1);
    if (result == NULL)
        return NULL;

    for (a = 0; a < 3; ++a)
        baseColor[a] = ((randomUInt() % 155) + 100) / 255.f;

    currentQuad = 0;
    currentVertex = 0;

    // longitude -pi to pi
    for (longitude = 0; longitude < longitudeCount; ++longitude)
    {

        // latitude 0 to pi/2
        for (latitude = latitudeBegin; latitude < latitudeEnd; ++latitude)
        {
            float t1 = -PI + longitude * 2 * PI / resol1;
            float t2 = -PI + (longitude + 1) * 2 * PI / resol1;
            float p1 = -PI / 2 + latitude * 2 * PI / resol2;
            float p2 = -PI / 2 + (latitude + 1) * 2 * PI / resol2;
            float r0, r1, r2, r3;

            r0 = ssFunc(t1, params);
            r1 = ssFunc(p1, &params[6]);
            r2 = ssFunc(t2, params);
            r3 = ssFunc(p2, &params[6]);

            if (r0 != 0 && r1 != 0 && r2 != 0 && r3 != 0)
            {
                VECTOR3 pa, pb, pc, pd;
                VECTOR3 v1, v2, n;
                float ca;
                int i;
                //float lenSq, invLenSq;

                superShapeMap(&pa, r0, r1, t1, p1);
                superShapeMap(&pb, r2, r1, t2, p1);
                superShapeMap(&pc, r2, r3, t2, p2);
                superShapeMap(&pd, r0, r3, t1, p2);

                // kludge to set lower edge of the object to fixed level
                if (latitude == latitudeBegin + 1)
                    pa.z = pb.z = 0;

                vector3Sub(&v1, &pb, &pa);
                vector3Sub(&v2, &pd, &pa);

                // Calculate normal with cross product.
                /*   i    j    k      i    j
                 * v1.x v1.y v1.z | v1.x v1.y
                 * v2.x v2.y v2.z | v2.x v2.y
                 */

                n.x = v1.y * v2.z - v1.z * v2.y;
                n.y = v1.z * v2.x - v1.x * v2.z;
                n.z = v1.x * v2.y - v1.y * v2.x;

                /* Pre-normalization of the normals is disabled here because
                 * they will be normalized anyway later due to automatic
                 * normalization (GL_NORMALIZE). It is enabled because the
                 * objects are scaled with glScale.
                 */
                /*
                lenSq = n.x * n.x + n.y * n.y + n.z * n.z;
                invLenSq = (float)(1 / sqrt(lenSq));
                n.x *= invLenSq;
                n.y *= invLenSq;
                n.z *= invLenSq;
                */

                ca = pa.z + 0.5f;

                for (i = currentVertex * 3;
                     i < (currentVertex + 6) * 3;
                     i += 3)
                {
                    result->normalArray[i] = FIXED(n.x);
                    result->normalArray[i + 1] = FIXED(n.y);
                    result->normalArray[i + 2] = FIXED(n.z);
                }
                for (i = currentVertex * 4;
                     i < (currentVertex + 6) * 4;
                     i += 4)
                {
                    int a, color[3];
                    for (a = 0; a < 3; ++a)
                    {
                        color[a] = (int)(ca * baseColor[a] * 255);
                        if (color[a] > 255) color[a] = 255;
                    }
                    result->colorArray[i] = (GLubyte)color[0];
                    result->colorArray[i + 1] = (GLubyte)color[1];
                    result->colorArray[i + 2] = (GLubyte)color[2];
                    result->colorArray[i + 3] = 0;
                }
                result->vertexArray[currentVertex * 3] = FIXED(pa.x);
                result->vertexArray[currentVertex * 3 + 1] = FIXED(pa.y);
                result->vertexArray[currentVertex * 3 + 2] = FIXED(pa.z);
                ++currentVertex;
                result->vertexArray[currentVertex * 3] = FIXED(pb.x);
                result->vertexArray[currentVertex * 3 + 1] = FIXED(pb.y);
                result->vertexArray[currentVertex * 3 + 2] = FIXED(pb.z);
                ++currentVertex;
                result->vertexArray[currentVertex * 3] = FIXED(pd.x);
                result->vertexArray[currentVertex * 3 + 1] = FIXED(pd.y);
                result->vertexArray[currentVertex * 3 + 2] = FIXED(pd.z);
                ++currentVertex;
                result->vertexArray[currentVertex * 3] = FIXED(pb.x);
                result->vertexArray[currentVertex * 3 + 1] = FIXED(pb.y);
                result->vertexArray[currentVertex * 3 + 2] = FIXED(pb.z);
                ++currentVertex;
                result->vertexArray[currentVertex * 3] = FIXED(pc.x);
                result->vertexArray[currentVertex * 3 + 1] = FIXED(pc.y);
                result->vertexArray[currentVertex * 3 + 2] = FIXED(pc.z);
                ++currentVertex;
                result->vertexArray[currentVertex * 3] = FIXED(pd.x);
                result->vertexArray[currentVertex * 3 + 1] = FIXED(pd.y);
                result->vertexArray[currentVertex * 3 + 2] = FIXED(pd.z);
                ++currentVertex;
            } // r0 && r1 && r2 && r3
            ++currentQuad;
        } // latitude
    } // longitude

    // Set number of vertices in object to the actual amount created.
    result->count = currentVertex;

    return result;
}


static GLOBJECT * createGroundPlane()
{
    const int scale = 4;
    const int yBegin = -15, yEnd = 15;    // ends are non-inclusive
    const int xBegin = -15, xEnd = 15;
    const long triangleCount = (yEnd - yBegin) * (xEnd - xBegin) * 2;
    const long vertices = triangleCount * 3;
    GLOBJECT *result;
    int x, y;
    long currentVertex, currentQuad;

    result = newGLObject(vertices, 2, 0);
    if (result == NULL)
        return NULL;

    currentQuad = 0;
    currentVertex = 0;

    for (y = yBegin; y < yEnd; ++y)
    {
        for (x = xBegin; x < xEnd; ++x)
        {
            GLubyte color;
            int i, a;
            color = (GLubyte)((randomUInt() & 0x5f) + 81);  // 101 1111
            for (i = currentVertex * 4; i < (currentVertex + 6) * 4; i += 4)
            {
                result->colorArray[i] = color;
                result->colorArray[i + 1] = color;
                result->colorArray[i + 2] = color;
                result->colorArray[i + 3] = 0;
            }

            // Axis bits for quad triangles:
            // x: 011100 (0x1c), y: 110001 (0x31)  (clockwise)
            // x: 001110 (0x0e), y: 100011 (0x23)  (counter-clockwise)
            for (a = 0; a < 6; ++a)
            {
                const int xm = x + ((0x1c >> a) & 1);
                const int ym = y + ((0x31 >> a) & 1);
                const float m = (float)(cos(xm * 2) * sin(ym * 4) * 0.75f);
                result->vertexArray[currentVertex * 2] =
                    FIXED(xm * scale + m);
                result->vertexArray[currentVertex * 2 + 1] =
                    FIXED(ym * scale + m);
                ++currentVertex;
            }
            ++currentQuad;
        }
    }
    return result;
}


static void drawGroundPlane()
{
    glDisable(GL_CULL_FACE);
    glDisable(GL_DEPTH_TEST);
    glEnable(GL_BLEND);
    glBlendFunc(GL_ZERO, GL_SRC_COLOR);
    glDisable(GL_LIGHTING);

    drawGLObject(sGroundPlane);

    glEnable(GL_LIGHTING);
    glDisable(GL_BLEND);
    glEnable(GL_DEPTH_TEST);
}


static void drawFadeQuad()
{
    static const GLfixed quadVertices[] = {
        -0x10000, -0x10000,
         0x10000, -0x10000,
        -0x10000,  0x10000,
         0x10000, -0x10000,
         0x10000,  0x10000,
        -0x10000,  0x10000
    };

    const int beginFade = sTick - sCurrentCamTrackStartTick;
    const int endFade = sNextCamTrackStartTick - sTick;
    const int minFade = beginFade < endFade ? beginFade : endFade;

    if (minFade < 1024)
    {
        const GLfixed fadeColor = minFade << 6;
        glColor4x(fadeColor, fadeColor, fadeColor, 0);

        glDisable(GL_DEPTH_TEST);
        glEnable(GL_BLEND);
        glBlendFunc(GL_ZERO, GL_SRC_COLOR);
        glDisable(GL_LIGHTING);

        glMatrixMode(GL_MODELVIEW);
        glLoadIdentity();

        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();

        glDisableClientState(GL_COLOR_ARRAY);
        glDisableClientState(GL_NORMAL_ARRAY);
        glVertexPointer(2, GL_FIXED, 0, quadVertices);
        glDrawArrays(GL_TRIANGLES, 0, 6);

        glEnableClientState(GL_COLOR_ARRAY);

        glMatrixMode(GL_MODELVIEW);

        glEnable(GL_LIGHTING);
        glDisable(GL_BLEND);
        glEnable(GL_DEPTH_TEST);
    }
}


// Called from the app framework.
void appInit()
{
    unsigned int a;

    glEnable(GL_NORMALIZE);
    glEnable(GL_DEPTH_TEST);
    glDisable(GL_CULL_FACE);
    glShadeModel(GL_FLAT);

    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glEnable(GL_LIGHT1);
    glEnable(GL_LIGHT2);

    glEnableClientState(GL_VERTEX_ARRAY);
    glEnableClientState(GL_COLOR_ARRAY);

    seedRandom(15);

    for (a = 0; a < SUPERSHAPE_COUNT; ++a)
    {
        sSuperShapeObjects[a] = createSuperShape(sSuperShapeParams[a]);
        assert(sSuperShapeObjects[a] != NULL);
    }
    sGroundPlane = createGroundPlane();
    assert(sGroundPlane != NULL);
}


// Called from the app framework.
void appDeinit()
{
    unsigned int a;
    for (a = 0; a < SUPERSHAPE_COUNT; ++a)
        freeGLObject(sSuperShapeObjects[a]);
    freeGLObject(sGroundPlane);
}


static void gluPerspective(GLfloat fovy, GLfloat aspect,
                           GLfloat zNear, GLfloat zFar)
{
    GLfloat xmin, xmax, ymin, ymax;

    ymax = zNear * (GLfloat)tan(fovy * PI / 360);
    ymin = -ymax;
    xmin = ymin * aspect;
    xmax = ymax * aspect;

    glFrustumx((GLfixed)(xmin * 65536), (GLfixed)(xmax * 65536),
               (GLfixed)(ymin * 65536), (GLfixed)(ymax * 65536),
               (GLfixed)(zNear * 65536), (GLfixed)(zFar * 65536));
}


static void prepareFrame(int width, int height)
{
    glViewport(0, 0, width, height);

    glClearColorx((GLfixed)(0.1f * 65536),
                  (GLfixed)(0.2f * 65536),
                  (GLfixed)(0.3f * 65536), 0x10000);
    glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45, (float)width / height, 0.5f, 150);

    glMatrixMode(GL_MODELVIEW);

    glLoadIdentity();
}


static void configureLightAndMaterial()
{
    static GLfixed light0Position[] = { -0x40000, 0x10000, 0x10000, 0 };
    static GLfixed light0Diffuse[] = { 0x10000, 0x6666, 0, 0x10000 };
    static GLfixed light1Position[] = { 0x10000, -0x20000, -0x10000, 0 };
    static GLfixed light1Diffuse[] = { 0x11eb, 0x23d7, 0x5999, 0x10000 };
    static GLfixed light2Position[] = { -0x10000, 0, -0x40000, 0 };
    static GLfixed light2Diffuse[] = { 0x11eb, 0x2b85, 0x23d7, 0x10000 };
    static GLfixed materialSpecular[] = { 0x10000, 0x10000, 0x10000, 0x10000 };

    glLightxv(GL_LIGHT0, GL_POSITION, light0Position);
    glLightxv(GL_LIGHT0, GL_DIFFUSE, light0Diffuse);
    glLightxv(GL_LIGHT1, GL_POSITION, light1Position);
    glLightxv(GL_LIGHT1, GL_DIFFUSE, light1Diffuse);
    glLightxv(GL_LIGHT2, GL_POSITION, light2Position);
    glLightxv(GL_LIGHT2, GL_DIFFUSE, light2Diffuse);
    glMaterialxv(GL_FRONT_AND_BACK, GL_SPECULAR, materialSpecular);

    glMaterialx(GL_FRONT_AND_BACK, GL_SHININESS, 60 << 16);
    glEnable(GL_COLOR_MATERIAL);
}


static void drawModels(float zScale)
{
    const int translationScale = 9;
    int x, y;

    seedRandom(9);

    glScalex(1 << 16, 1 << 16, (GLfixed)(zScale * 65536));

    for (y = -5; y <= 5; ++y)
    {
        for (x = -5; x <= 5; ++x)
        {
            float buildingScale;
            GLfixed fixedScale;

            int curShape = randomUInt() % SUPERSHAPE_COUNT;
            buildingScale = sSuperShapeParams[curShape][SUPERSHAPE_PARAMS - 1];
            fixedScale = (GLfixed)(buildingScale * 65536);

            glPushMatrix();
            glTranslatex((x * translationScale) * 65536,
                         (y * translationScale) * 65536,
                         0);
            glRotatex((GLfixed)((randomUInt() % 360) << 16), 0, 0, 1 << 16);
            glScalex(fixedScale, fixedScale, fixedScale);

            drawGLObject(sSuperShapeObjects[curShape]);
            glPopMatrix();
        }
    }

    for (x = -2; x <= 2; ++x)
    {
        const int shipScale100 = translationScale * 500;
        const int offs100 = x * shipScale100 + (sTick % shipScale100);
        float offs = offs100 * 0.01f;
        GLfixed fixedOffs = (GLfixed)(offs * 65536);
        glPushMatrix();
        glTranslatex(fixedOffs, -4 * 65536, 2 << 16);
        drawGLObject(sSuperShapeObjects[SUPERSHAPE_COUNT - 1]);
        glPopMatrix();
        glPushMatrix();
        glTranslatex(-4 * 65536, fixedOffs, 4 << 16);
        glRotatex(90 << 16, 0, 0, 1 << 16);
        drawGLObject(sSuperShapeObjects[SUPERSHAPE_COUNT - 1]);
        glPopMatrix();
    }
}


/* Following gluLookAt implementation is adapted from the
 * Mesa 3D Graphics library. http://www.mesa3d.org
 */
static void gluLookAt(GLfloat eyex, GLfloat eyey, GLfloat eyez,
                  GLfloat centerx, GLfloat centery, GLfloat centerz,
                  GLfloat upx, GLfloat upy, GLfloat upz)
{
    GLfloat m[16];
    GLfloat x[3], y[3], z[3];
    GLfloat mag;

    /* Make rotation matrix */

    /* Z vector */
    z[0] = eyex - centerx;
    z[1] = eyey - centery;
    z[2] = eyez - centerz;
    mag = (float)sqrt(z[0] * z[0] + z[1] * z[1] + z[2] * z[2]);
    if (mag) {            /* mpichler, 19950515 */
        z[0] /= mag;
        z[1] /= mag;
        z[2] /= mag;
    }

    /* Y vector */
    y[0] = upx;
    y[1] = upy;
    y[2] = upz;

    /* X vector = Y cross Z */
    x[0] = y[1] * z[2] - y[2] * z[1];
    x[1] = -y[0] * z[2] + y[2] * z[0];
    x[2] = y[0] * z[1] - y[1] * z[0];

    /* Recompute Y = Z cross X */
    y[0] = z[1] * x[2] - z[2] * x[1];
    y[1] = -z[0] * x[2] + z[2] * x[0];
    y[2] = z[0] * x[1] - z[1] * x[0];

    /* mpichler, 19950515 */
    /* cross product gives area of parallelogram, which is < 1.0 for
     * non-perpendicular unit-length vectors; so normalize x, y here
     */

    mag = (float)sqrt(x[0] * x[0] + x[1] * x[1] + x[2] * x[2]);
    if (mag) {
        x[0] /= mag;
        x[1] /= mag;
        x[2] /= mag;
    }

    mag = (float)sqrt(y[0] * y[0] + y[1] * y[1] + y[2] * y[2]);
    if (mag) {
        y[0] /= mag;
        y[1] /= mag;
        y[2] /= mag;
    }

#define M(row,col)  m[(col)*4+(row)]
    M(0, 0) = x[0];
    M(0, 1) = x[1];
    M(0, 2) = x[2];
    M(0, 3) = 0.0;
    M(1, 0) = y[0];
    M(1, 1) = y[1];
    M(1, 2) = y[2];
    M(1, 3) = 0.0;
    M(2, 0) = z[0];
    M(2, 1) = z[1];
    M(2, 2) = z[2];
    M(2, 3) = 0.0;
    M(3, 0) = 0.0;
    M(3, 1) = 0.0;
    M(3, 2) = 0.0;
    M(3, 3) = 1.0;
#undef M
    {
        int a;
        GLfixed fixedM[16];
        for (a = 0; a < 16; ++a)
            fixedM[a] = (GLfixed)(m[a] * 65536);
        glMultMatrixx(fixedM);
    }

    /* Translate Eye to Origin */
    glTranslatex((GLfixed)(-eyex * 65536),
                 (GLfixed)(-eyey * 65536),
                 (GLfixed)(-eyez * 65536));
}


static void camTrack()
{
    float lerp[5];
    float eX, eY, eZ, cX, cY, cZ;
    float trackPos;
    CAMTRACK *cam;
    long currentCamTick;
    int a;

    if (sNextCamTrackStartTick <= sTick)
    {
        ++sCurrentCamTrack;
        sCurrentCamTrackStartTick = sNextCamTrackStartTick;
    }
    sNextCamTrackStartTick = sCurrentCamTrackStartTick +
                             sCamTracks[sCurrentCamTrack].len * CAMTRACK_LEN;

    cam = &sCamTracks[sCurrentCamTrack];
    currentCamTick = sTick - sCurrentCamTrackStartTick;
    trackPos = (float)currentCamTick / (CAMTRACK_LEN * cam->len);

    for (a = 0; a < 5; ++a)
        lerp[a] = (cam->src[a] + cam->dest[a] * trackPos) * 0.01f;

    if (cam->dist)
    {
        float dist = cam->dist * 0.1f;
        cX = lerp[0];
        cY = lerp[1];
        cZ = lerp[2];
        eX = cX - (float)cos(lerp[3]) * dist;
        eY = cY - (float)sin(lerp[3]) * dist;
        eZ = cZ - lerp[4];
    }
    else
    {
        eX = lerp[0];
        eY = lerp[1];
        eZ = lerp[2];
        cX = eX + (float)cos(lerp[3]);
        cY = eY + (float)sin(lerp[3]);
        cZ = eZ + lerp[4];
    }
    gluLookAt(eX, eY, eZ, cX, cY, cZ, 0, 0, 1);
}


// Called from the app framework.
/* The tick is current time in milliseconds, width and height
 * are the image dimensions to be rendered.
 */
void appRender(long tick, int width, int height)
{
    if (sStartTick == 0)
        sStartTick = tick;
    if (!gAppAlive)
        return;

    // Actual tick value is "blurred" a little bit.
    sTick = (sTick + tick - sStartTick) >> 1;

    // Terminate application after running through the demonstration once.
    if (sTick >= RUN_LENGTH)
    {
        gAppAlive = 0;
        return;
    }

    // Prepare OpenGL ES for rendering of the frame.
    prepareFrame(width, height);

    // Update the camera position and set the lookat.
    camTrack();

    // Configure environment.
    configureLightAndMaterial();

    // Draw the reflection by drawing models with negated Z-axis.
    glPushMatrix();
    drawModels(-1);
    glPopMatrix();

    // Blend the ground plane to the window.
    drawGroundPlane();

    // Draw all the models normally.
    drawModels(1);

    // Draw fade quad over whole window (when changing cameras).
    drawFadeQuad();
}

通过上面的示例可以看到OpenGL EGL炫彩的世界，并且C++和Java结合就能一起构建诸多复杂美丽的图形。
并且实现方式跟前一篇文章是相呼应的。

(四)、参考文档：

【EGL函数API文档】
【OpenGL ES EGL介绍】