公轉(zhuǎn)和自轉(zhuǎn)是OpenGL中的一個(gè)經(jīng)典案例耻矮，先來看看效果：

效果圖

方法分析

1秦躯、對(duì)圖形數(shù)據(jù)初始化，需要調(diào)用setupRC()方法
2裆装、窗口大小變動(dòng)時(shí)踱承，需要調(diào)用changeSize(int,int)方法
3、每次繪制時(shí)哨免，需要調(diào)用RenderScene()方法
4茎活、按鍵盤移動(dòng)，需要調(diào)用SpecialKey(int,int,int)方法

變量分析

1铁瞒、地面容器 GLBatch floorBatch
2妙色、紅色球體 GLTriangleBatch redBatch
3、藍(lán)色球體 GLTriangleBatch blueBatch
4慧耍、 觀察者 GLFrame camera
5、遠(yuǎn)處球體坐標(biāo) GLFrame spheres[NUM_SPHERES]

運(yùn)行流程：

1丐谋、main函數(shù)中先進(jìn)行初始化設(shè)置
2芍碧、在SetupRC中初始化圖形參數(shù)
3、設(shè)置視圖尺寸觸發(fā)changSize()
4号俐、每次渲染時(shí)執(zhí)行RenderScene()
5泌豆、鍵盤輸入執(zhí)行SpecialKey()后，會(huì)調(diào)用RenderSecene()
6吏饿、自轉(zhuǎn)公轉(zhuǎn)需要定時(shí)器踪危，定時(shí)器每秒鐘會(huì)觸發(fā)重新渲染調(diào)用RenderSecene()

執(zhí)行順序

具體個(gè)方法實(shí)現(xiàn)

1、main函數(shù)

int main(int argc,char *argv[]) {

    //初始化GLUT庫
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA|GLUT_DEPTH|GLUT_STENCIL)
 
    //設(shè)置GLUT窗口大小與標(biāo)題
    glutInitWindowSize(1920, 1080);
    glutCreateWindow("Floor");
   
    //指定窗口改變時(shí)調(diào)用的方法
    glutReshapeFunc(changeSize);
    //指定渲染時(shí)調(diào)用的方法
    glutDisplayFunc(RenderScene);
    //指定鍵盤輸入時(shí)調(diào)用的方法
    glutSpecialFunc(SpecialKey);
    //判斷驅(qū)動(dòng)器有沒有問題
    GLenum status = glewInit();
    if (GLEW_OK != status)  {
                return 0;
    }
    
    //初始化渲染環(huán)境
    setupRC();
    //執(zhí)行l(wèi)oop循環(huán)
    glutMainLoop();
    return  0;
}

2猪落、changsize函數(shù)

void changeSize(int w,int h) {
    //設(shè)置窗口
    glViewport(0, 0, w, h);
    
    //設(shè)置投影矩陣贞远，因?yàn)橥队熬仃囆枰翱陂L(zhǎng)寬比，所以在changsize中設(shè)置
    viewFrustum.SetPerspective(35, float(w)/float(h), 1, 100);
    projectionMatrix.LoadMatrix(viewFrustum.GetProjectionMatrix());
   //模型矩陣笨忌，視圖矩陣加入管道蓝仲，便于取用
    transform.SetMatrixStacks(modelMatrix, projectionMatrix);
}

3、setupRC函數(shù)

void setupRC() {
    //清除遺留背景色并設(shè)置背景色
    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
    //初始化著色器
    shaderManager.InitializeStockShaders();
    //開啟深度測(cè)試
    glEnable(GL_DEPTH_TEST);
    camera.RotateWorld(float(m3dDegToRad(180.0f)), 0, 1, 0);
    
    //地面的坐標(biāo)
    floorBatch.Begin(GL_LINES, 324);
    for(GLfloat x = -20.0; x <= 20.0f; x+= 0.5) {
        floorBatch.Vertex3f(x, -0.55f, 20.0f);
        floorBatch.Vertex3f(x, -0.55f, -20.0f);
        
        floorBatch.Vertex3f(20.0f, -0.55f, x);
        floorBatch.Vertex3f(-20.0f, -0.55f, x);
    }
    floorBatch.End();
    
    //紅球
    gltMakeSphere(redBatch, 0.5f, 100, 100);
    //藍(lán)球
    gltMakeSphere(blueBatch, 0.1f, 20, 20);
    
    //隨機(jī)位置放置藍(lán)球
    for (int i = 0; i < NUM_SPHERES; i++) {
        //y軸不變，X,Z產(chǎn)生隨機(jī)值
        GLfloat x = ((GLfloat)((rand() % 400) - 200 ) * 0.1f);
        GLfloat z = ((GLfloat)((rand() % 400) - 200 ) * 0.1f);
        //在y方向袱结，將球體設(shè)置為0.0的位置亮隙，這使得它們看起來是飄浮在眼睛的高度
        //對(duì)spheres數(shù)組中的每一個(gè)頂點(diǎn)，設(shè)置頂點(diǎn)數(shù)據(jù)
        spheres[i].SetOrigin(x, 0.0f, -z);
    }
}

4垢夹、SpecialKey函數(shù)

void SpecialKey(int keys, int x, int y) {
    //每次移動(dòng)的距離
    GLfloat line = 1;
    //每次旋轉(zhuǎn)的弧度
    float angular = float(m3dDegToRad(5.0f));

    if (keys == GLUT_KEY_UP) {
        camera.MoveForward(line);
    }
    if (keys == GLUT_KEY_DOWN) {
        camera.MoveForward(-line);
    }
    if (keys == GLUT_KEY_LEFT) {
        camera.RotateWorld(angular, 0, 1, 0);
    }
    if (keys == GLUT_KEY_RIGHT) {
        camera.RotateWorld(-angular, 0, 1, 0);
    }
}

5溢吻、RenderScene函數(shù)

void RenderScene(void) {
    //清空顏色緩存區(qū)和深度緩存區(qū)
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    //地板顏色
    static GLfloat floorC[] = {0,1,0,1};
    //紅球顏色
    static GLfloat redC[] = {1,0,0,1};
    //籃球顏色
    static GLfloat blueC[] = {0,0,1,1};
    //定時(shí)器
    static CStopWatch timer;
    float yRot = timer.GetElapsedSeconds()*60;
    //光源位置
    M3DVector4f light = {0.0f,10.0f,5.0f,1.0f};
    //拷貝一份棧頂?shù)臓顟B(tài)并放入棧頂
    modelMatrix.PushMatrix();
    //觀察者移動(dòng)
    M3DMatrix44f mCamera;
    camera.GetMatrix(mCamera);
    modelMatrix.PushMatrix(mCamera);
    //繪制地面
    shaderManager.UseStockShader(GLT_SHADER_FLAT, transform.GetModelViewProjectionMatrix(),floorC);
    floorBatch.Draw();
    
    //紅球
    //紅球向屏幕內(nèi)移動(dòng)
    modelMatrix.Translate(0, 0, -3);
    //紅球自轉(zhuǎn)需要保存自轉(zhuǎn)前的狀態(tài)，先進(jìn)行拷貝入棧
    modelMatrix.PushMatrix();
   //紅球自轉(zhuǎn)
    modelMatrix.Rotate(yRot, 0, 1, 0);
    shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transform.GetModelViewMatrix(), transform.GetProjectionMatrix(), light, redC);
    redBatch.Draw();
    modelMatrix.PopMatrix();

    //藍(lán)色小球
    for (int i = 0; i < NUM_SPHERES; i++) {
        modelMatrix.PushMatrix();
        modelMatrix.MultMatrix(spheres[i]);
        shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transform.GetModelViewMatrix(), transform.GetProjectionMatrix(), light, blueC);        blueBatch.Draw();
        modelMatrix.PopMatrix();
    }
    
    //公轉(zhuǎn)
    modelMatrix.Rotate(yRot*-3.0, 0, 1, 0);
    modelMatrix.Translate(0.8f, 0, 0);
    shaderManager.UseStockShader(GLT_SHADER_POINT_LIGHT_DIFF, transform.GetModelViewMatrix(), transform.GetProjectionMatrix(), light, blueC);
    blueBatch.Draw();
    modelMatrix.PopMatrix();
    modelMatrix.PopMatrix();
    glutSwapBuffers();
    glutPostRedisplay();
}