OpenGL旋转场景不如预期

Posted 2023-02-21

【中文标题】OpenGL旋转场景不如预期

【英文标题】：OpenGL rotate scene not as expected

【发布时间】：2015-07-04 02:03:41

【问题描述】：

使用我的代码，当我旋转模型视图时；它单独旋转每个对象。 我正在尝试旋转整个视图平面。我怎样才能做到这一点？

我知道 gluLookAt，但我正试图了解这背后的数学原理。

这是我的代码： Prepare_scene 仅在 opengl init 和窗口重塑时调用

// prepare_scene
    glViewport(0, 0, windowWidth, windowHeight); 

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity(); 

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();

    glOrtho(0, windowWidth, 0, windowHeight, 0, 40); 

    glEnable(GL_DEPTH_TEST);    

    glShadeModel(GL_SMOOTH);                            // Enable Smooth Shading

    glClearDepth(1.0f);                                 // Depth Buffer Setup
    glEnable(GL_DEPTH_TEST);                            // Enables Depth Testing
    glDepthFunc(GL_LEQUAL);                             // The Type Of Depth Testing To Do
    glHint(GL_POINT_SMOOTH_HINT, GL_NICEST);

    glEnable(GL_POINT_SMOOTH);
    glPointSize(4); 

    glClearColor(0.0f, 0.0f, 0.0f, 1);

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

每个绘图帧都会调用渲染

// render

        glClearColor(0.0f, 0.0f, 0.0f, 1); // black
        //glClearColor(1.0f, 1.0f, 1.0f, 1); // white
        glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
        //

        // try to control the camera
        // push_matrix (and at the end of render, add pop_matrix)
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix();

        glTranslatef(eye_x, eye_y, eye_z);
        glRotatef(x_angular, 0, 1, 0); 

        // Go back to projection mode
        glMatrixMode(GL_PROJECTION);

        GLfloat mat_black[] = 0.0,0.0,0.0, 1.0;
        // Transparent white-grey window
        GLfloat mat_specular_w[] = 0.8,0.88,0.88, 1.0;
        GLfloat mat_shine_w[] = 20.0;

        glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular_w);
        glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_specular_w);
        glMaterialfv(GL_FRONT, GL_AMBIENT, mat_specular_w);
        glMaterialfv(GL_FRONT, GL_SHININESS, mat_shine_w);  


        // for each object in objects:
                glPushMatrix();

                // object "world coordinates"
                // in glTranslatef(x,y,z); // z is always 0; for this test
                glTranslatef( (*obj_i)->anchor[0] , (*obj_i)->anchor[1], (*obj_i)->anchor[2]);
                glutWireSphere((*obj_i)->r, 15, 15);
                //glutSolidSphere((*obj_i)->r, 30, 30); // (*obj_i)->r

                glPopMatrix();



        glMatrixMode(GL_MODELVIEW);
        glPopMatrix();

        glFlush();

        SwapBuffers(hdc);

【参考方案1】：

Stop doin' weird camera/object stuff the GL_PROJECTION 堆栈。

将其保存为GL_MODELVIEW：

// Every frame

glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// do projection matrix stuff here (gluPerspective(), glOrtho(), etc.)
glOrtho(0, windowWidth, 0, windowHeight, 0, 40); 

glMatrixMode(GL_MODELVIEW);
glLoadIdentity(); 
// do camera transform (gluLookAt(), etc.) here
// I'm guessing this was your camera transform(s):
glTranslatef(eye_x, eye_y, eye_z);
glRotatef(x_angular, 0, 1, 0); 

// foreach object:
glPushMatrix();

    // do whatever
    glTranslatef( (*obj_i)->anchor[0] , (*obj_i)->anchor[1], (*obj_i)->anchor[2]);
    ...

glPopMatrix();