OpenGL 隧道和星球镜像案例解析

案例一: 隧道

1.1 最终效果

1.2 整体流程

1.3 核心代码

1.3.1 初始化纹理数据、设置墙体顶点和纹理映射坐标

void setupRC(void) {
    // 设置窗口背景色
    glClearColor(0, 0, 0, 1);
    // 初始化存储着色器
    shaderManager.InitializeStockShaders();
    
    // 纹理加载
    GLbyte *pBytes;
    GLint iWidth, iHeight, iComponents;
    GLenum eFormat;
    GLint iLoop;
    
    // 生成纹理标记
    glGenTextures(TEXTURE_COUNT, textures);
    
    // 循环设置纹理数组的纹理参数
    for (iLoop = 0; iLoop < TEXTURE_COUNT; iLoop++) {
        glBindTexture(GL_TEXTURE_2D, textures[iLoop]);
        
        pBytes = gltReadTGABits(szTextureFiles[iLoop], &iWidth, &iHeight, &iComponents, &eFormat);
        
        // 设置纹理参数-过滤
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
        
        // 纹理参数-环绕
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
        glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
        
        // 纹理载入
        glTexImage2D(GL_TEXTURE_2D, 0, iComponents, iWidth, iHeight, 0, eFormat, GL_UNSIGNED_BYTE, pBytes);
        
        // 生成 mip 贴图
        glGenerateMipmap(GL_TEXTURE_2D);
        // 释放
        free(pBytes);
    }
    
    // 设置顶点
    GLfloat z;
    
    floorBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);
    //参考图 1-1
    //Z表示深度，隧道的深度
    for(z = 60.0f; z >= 0.0f; z -=10.0f)
    {
        floorBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
        floorBatch.Vertex3f(-10.0f, -10.0f, z);
        
        floorBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
        floorBatch.Vertex3f(10.0f, -10.0f, z);
        
        floorBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
        floorBatch.Vertex3f(-10.0f, -10.0f, z - 10.0f);
        
        floorBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
        floorBatch.Vertex3f(10.0f, -10.0f, z - 10.0f);
    }
    floorBatch.End();
   
   //参考图 1-2
    ceilingBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);
    for(z = 60.0f; z >= 0.0f; z -=10.0f)
    {
        ceilingBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
        ceilingBatch.Vertex3f(-10.0f, 10.0f, z - 10.0f);
        
        ceilingBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
        ceilingBatch.Vertex3f(10.0f, 10.0f, z - 10.0f);
        
        ceilingBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
        ceilingBatch.Vertex3f(-10.0f, 10.0f, z);
        
        ceilingBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
        ceilingBatch.Vertex3f(10.0f, 10.0f, z);
    }
    ceilingBatch.End();
    
    //参考图 1-3
    leftWallBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);
    for(z = 60.0f; z >= 0.0f; z -=10.0f)
    {
        leftWallBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
        leftWallBatch.Vertex3f(-10.0f, -10.0f, z);
        
        leftWallBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
        leftWallBatch.Vertex3f(-10.0f, 10.0f, z);
        
        leftWallBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
        leftWallBatch.Vertex3f(-10.0f, -10.0f, z - 10.0f);
        
        leftWallBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
        leftWallBatch.Vertex3f(-10.0f, 10.0f, z - 10.0f);
    }
    leftWallBatch.End();
   
   //参考图 1-4
    rightWallBatch.Begin(GL_TRIANGLE_STRIP, 28, 1);
    for(z = 60.0f; z >= 0.0f; z -=10.0f)
    {
        rightWallBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
        rightWallBatch.Vertex3f(10.0f, -10.0f, z);
        
        rightWallBatch.MultiTexCoord2f(0, 0.0f, 1.0f);
        rightWallBatch.Vertex3f(10.0f, 10.0f, z);
        
        rightWallBatch.MultiTexCoord2f(0, 1.0f, 0.0f);
        rightWallBatch.Vertex3f(10.0f, -10.0f, z - 10.0f);
        
        rightWallBatch.MultiTexCoord2f(0, 1.0f, 1.0f);
        rightWallBatch.Vertex3f(10.0f, 10.0f, z - 10.0f);
    }
    rightWallBatch.End();
}

• 图 1-1

  

• 图 1-2

  

• 图 1-3

  

• 图 1-4

  

1.3.2 渲染

void RenderScence(void) {
    // 删除要用到的缓冲区
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
    // 设置一组浮点数表示红色
    GLfloat vRed[] = {1.0f, 0.0f, 0.0f, 1.0f};
    
    modelViewMatrix.PushMatrix();
    
    modelViewMatrix.Translate(0, 0, viewZ);
    
    // 设置纹理替换着色器
    shaderManager.UseStockShader(GLT_SHADER_TEXTURE_REPLACE, transformPipeline.GetModelViewProjectionMatrix(), 0);
    
    // 绘制地板
    glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_FLOOR]);
    floorBatch.Draw();

    // 绘制天花板
    glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_CEILING]);
    ceilingBatch.Draw();
    
    // 绘制左墙、右墙
    glBindTexture(GL_TEXTURE_2D, textures[TEXTURE_BRICK]);
    leftWallBatch.Draw();
    rightWallBatch.Draw();

    modelViewMatrix.PopMatrix();
    
    // 开始在后台缓冲区进行渲染，然后在结束时交换到前台
    glutSwapBuffers();
}

案例二：星球镜像

2.1 最终效果

2.2 整体流程

2.3 核心代码

2.3.1 初始化纹理数据、初始化球体顶点数据或角色帧

void setupRC(void) {
    glClearColor(0, 0, 0, 1);
    shaderManager.InitializeStockShaders();
    
    glEnable(GL_DEPTH_TEST);
    glEnable(GL_CULL_FACE);
    
    //3. 设置地板顶点数据&地板纹理
    GLfloat texSize = 10.0f;
    floorBatch.Begin(GL_TRIANGLE_FAN, 4,1);
    floorBatch.MultiTexCoord2f(0, 0.0f, 0.0f);
    floorBatch.Vertex3f(-20.f, -0.41f, 20.0f);
    
    floorBatch.MultiTexCoord2f(0, texSize, 0.0f);
    floorBatch.Vertex3f(20.0f, -0.41f, 20.f);
    
    floorBatch.MultiTexCoord2f(0, texSize, texSize);
    floorBatch.Vertex3f(20.0f, -0.41f, -20.0f);
    
    floorBatch.MultiTexCoord2f(0, 0.0f, texSize);
    floorBatch.Vertex3f(-20.0f, -0.41f, -20.0f);
    floorBatch.End();
    
    gltMakeSphere(torusBatch, 0.4f, 40, 80);
    
    gltMakeSphere(sphereBatch, 0.1f, 26, 13);
    
    for (int i = 0; i < NUM_SPHERES; i++) {
        // 创建同一平面的小球，要求y值一样。
        GLfloat x = ((GLfloat)((rand() % 400) - 200) * 0.1f);
        GLfloat z = ((GLfloat)((rand() % 400) - 200) * 0.1f);
        
        spheres[i].SetOrigin(x, 0.0f, z);
    }
    
    glGenTextures(3, uiTextures);
    
    glBindTexture(GL_TEXTURE_2D, uiTextures[0]);
    LoadTGATexture("marble.tga", GL_LINEAR_MIPMAP_LINEAR, GL_LINEAR, GL_REPEAT);
    
    glBindTexture(GL_TEXTURE_2D, uiTextures[1]);
    LoadTGATexture("marslike.tga", GL_LINEAR_MIPMAP_LINEAR,
                   GL_LINEAR, GL_CLAMP_TO_EDGE);
    
    
    glBindTexture(GL_TEXTURE_2D, uiTextures[2]);
    LoadTGATexture("moonlike.tga", GL_LINEAR_MIPMAP_LINEAR,
                   GL_LINEAR, GL_CLAMP_TO_EDGE);
}

2.3.2加载纹理函数

bool LoadTGATexture(const char *szFileName, GLenum minFilter, GLenum magFilter, GLenum wrapMode) {
    GLbyte *pBits;
    int nWidth, nHeight, nComponents;
    GLenum eFormat;
    
    //1.读取纹理数据
    pBits = gltReadTGABits(szFileName, &nWidth, &nHeight, &nComponents, &eFormat);
    if(pBits == NULL)
        return false;
    
    //2、设置纹理参数
    //参数1：纹理维度
    //参数2：为S/T坐标设置模式
    //参数3：wrapMode,环绕模式
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, wrapMode);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, wrapMode);
    
    //参数1：纹理维度
    //参数2：线性过滤
    //参数3：wrapMode,环绕模式
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, minFilter);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, magFilter);
    
    //3.载入纹理
    //参数1：纹理维度
    //参数2：mip贴图层次
    //参数3：纹理单元存储的颜色成分（从读取像素图是获得）-将内部参数nComponents改为了通用压缩纹理格式GL_COMPRESSED_RGB
    //参数4：加载纹理宽
    //参数5：加载纹理高
    //参数6：加载纹理的深度
    //参数7：像素数据的数据类型（GL_UNSIGNED_BYTE，每个颜色分量都是一个8位无符号整数）
    //参数8：指向纹理图像数据的指针
    glTexImage2D(GL_TEXTURE_2D, 0, GL_COMPRESSED_RGB, nWidth, nHeight, 0,
                 eFormat, GL_UNSIGNED_BYTE, pBits);
    
    //使用完毕释放pBits
    free(pBits);
    
    //只有minFilter 等于以下四种模式，才可以生成Mip贴图
    //GL_NEAREST_MIPMAP_NEAREST具有非常好的性能，并且闪烁现象非常弱
    //GL_LINEAR_MIPMAP_NEAREST常常用于对游戏进行加速，它使用了高质量的线性过滤器
    //GL_LINEAR_MIPMAP_LINEAR 和GL_NEAREST_MIPMAP_LINEAR 过滤器在Mip层之间执行了一些额外的插值，以消除他们之间的过滤痕迹。
    //GL_LINEAR_MIPMAP_LINEAR 三线性Mip贴图。纹理过滤的黄金准则，具有最高的精度。
    if(minFilter == GL_LINEAR_MIPMAP_LINEAR ||
       minFilter == GL_LINEAR_MIPMAP_NEAREST ||
       minFilter == GL_NEAREST_MIPMAP_LINEAR ||
       minFilter == GL_NEAREST_MIPMAP_NEAREST)
    //4.加载Mip,纹理生成所有的Mip层
    //参数：GL_TEXTURE_1D、GL_TEXTURE_2D、GL_TEXTURE_3D
    glGenerateMipmap(GL_TEXTURE_2D);
    
    
    return true;
}

2.3.3 渲染方法

void RenderScence(void) {
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    // 地板颜色
    static GLfloat vFloorColor[] = {1.0f,1.0f,0.0f,0.75f};
    
    static CStopWatch rotTimer;
    float yRot = rotTimer.GetElapsedSeconds() * 60.0f;
    
    /* 单元矩阵 -> 旋转 -> 移动 -> 缩放 -> 出栈*/
    modelViewMatrix.PushMatrix();
    
    M3DMatrix44f mCamera;
    cameraFrame.GetCameraMatrix(mCamera);
    modelViewMatrix.MultMatrix(mCamera);
    
    // 压栈，开始绘制镜面内容
    modelViewMatrix.PushMatrix();
    
    // 添加反光效果
    modelViewMatrix.Scale(1, -1, 1);
    modelViewMatrix.Translate(0.0f, 0.8f, 0.0f);
    
    // 发生翻转，设置正面旋转方向
    glFrontFace(GL_CW);
    
    // 绘制镜面内容
    drawSomething(yRot);
    
    // 绘制完翻转回来
    glFrontFace(GL_CCW);
    
    // 绘制完镜面内容，出栈
    modelViewMatrix.PopMatrix();
    
    // 绘制地板
    // 开启混合
    glEnable(GL_BLEND);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    
    // 绑定纹理
    glBindTexture(GL_TEXTURE_2D, uiTextures[0]);
    
    // 纹理调整着色器（基本色*纹理混合）
    shaderManager.UseStockShader(GLT_SHADER_TEXTURE_MODULATE, transformPipeline.GetModelViewProjectionMatrix(), vFloorColor, 0);
    floorBatch.Draw();
    
    // 关闭混合
    glDisable(GL_BLEND);
    
    // 绘制镜面以上
    drawSomething(yRot);
    
    // 绘制完毕，恢复矩阵
    modelViewMatrix.PopMatrix();
    
    glutSwapBuffers();
    // 触发重新渲染
    glutPostRedisplay();
}

2.3.4 绘制镜面数据方法

void drawSomething(GLfloat yRot) {
    //1.定义光源位置&漫反射颜色
    static GLfloat vWhite[] = { 1.0f, 1.0f, 1.0f, 1.0f };
    static GLfloat vLightPos[] = { 0.0f, 3.0f, 0.0f, 1.0f };
    
    // 绘制小球
    glBindTexture(GL_TEXTURE_2D, uiTextures[2]);
    for (int i = 0; i < NUM_SPHERES; i++) {
        modelViewMatrix.PushMatrix();
        modelViewMatrix.MultMatrix(spheres[i]);
        shaderManager.UseStockShader(GLT_SHADER_TEXTURE_POINT_LIGHT_DIFF, modelViewMatrix.GetMatrix(), transformPipeline.GetProjectionMatrix(), vLightPos, vWhite, 0);
        sphereBatch.Draw();
        modelViewMatrix.PopMatrix();
    }
    
    // 绘制大球
    modelViewMatrix.Translate(0.0f, 0.2f, -2.5f);
    modelViewMatrix.PushMatrix();
    modelViewMatrix.Rotate(yRot, 0.0f, 1.0f, 0.0f);
    glBindTexture(GL_TEXTURE_2D, uiTextures[1]);
    shaderManager.UseStockShader(GLT_SHADER_TEXTURE_POINT_LIGHT_DIFF, modelViewMatrix.GetMatrix(), transformPipeline.GetProjectionMatrix(), vLightPos, vWhite, 0);
    torusBatch.Draw();
    modelViewMatrix.PopMatrix();
    
    // 绘制公转小球
    modelViewMatrix.PushMatrix();
    modelViewMatrix.Rotate(yRot * -2.0f, 0.0f, 1.0f, 0.0f);
    modelViewMatrix.Translate(0.8f, 0.0f, 0.0f);
    glBindTexture(GL_TEXTURE_2D, uiTextures[2]);
    shaderManager.UseStockShader(GLT_SHADER_TEXTURE_POINT_LIGHT_DIFF, modelViewMatrix.GetMatrix(), transformPipeline.GetProjectionMatrix(), vLightPos, vWhite, 0);
    sphereBatch.Draw();
    modelViewMatrix.PopMatrix();
}