c++ - 转动相机后，形状倾斜 OpenGL

Question

在Y轴和X轴上的相机旋转以及随后的移动之后，是一个奇怪的相机沿Z轴的旋转。
例如，这里是正常状态

但我在舞台上随意移动，全都扭曲了

我不知道该怎么做以及如何解决这个问题，我希望得到你的帮助。
我看到这个问题，它对我没有帮助，因为我什至不使用glm , 不要标记为重复。

代码:

#include <iostream>
#include <chrono>
#include <GL/glut.h>
#include "Camera.h"

using namespace std;

constexpr auto FPS_RATE = 120;
int windowHeight = 600, windowWidth = 600, windowDepth = 600;
float angle = 0, speedRatio = 0.25;
struct MyPoint3f
{
    float x;
    float y;
    float z;
};
MyPoint3f lastMousePos = { };
bool mouseButtonWasPressed = false;
float mouseSensitivity = 0.1;
float camMoveSpeed = 3;
float camPitchAngle = 0, camYawAngle = 0;
Camera cam;

void init();
void displayFunction();
void idleFunction();
void reshapeFunction(int, int);
void keyboardFunction(unsigned char, int, int);
void specialKeysFunction(int, int, int);
void mouseFunc(int, int, int, int);
void motionFunction(int, int);
double getTime();

double getTime()
{
    using Duration = std::chrono::duration<double>;
    return std::chrono::duration_cast<Duration>(
        std::chrono::high_resolution_clock::now().time_since_epoch()
        ).count();
}

const double frame_delay = 1.0 / FPS_RATE;
double last_render = 0;

void init()
{
    glutDisplayFunc(displayFunction);
    glutIdleFunc(idleFunction);
    glutReshapeFunc(reshapeFunction);
    glutKeyboardFunc(keyboardFunction);
    glutMouseFunc(mouseFunc);
    glutMotionFunc(motionFunction);
    glViewport(0, 0, windowWidth, windowHeight);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glFrustum(-windowWidth / 2, windowWidth / 2, -windowHeight / 2, windowHeight / 2, -windowDepth / 2, windowDepth / 2);
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    cam.setShape(45, (double)windowWidth / windowHeight, 0.1, 1000);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    cam.set(Point3(0, 0, 350), Point3(0, 0, 349), Vector3(0, 1, 0));
}

void displayFunction()
{
    angle += speedRatio;
    if (angle >= 360 || angle <= -360) angle = 0;
    if (camPitchAngle <= -360) camPitchAngle = 0;
    if (camPitchAngle >= 360) camPitchAngle = 0;
    if (camYawAngle <= -360) camYawAngle = 0;
    if (camYawAngle >= 360) camYawAngle = 0;
    cout << camPitchAngle << " " << camYawAngle << endl;
    cam.pitch(-(camPitchAngle *= mouseSensitivity));
    cam.yaw(-(camYawAngle *= mouseSensitivity));
    camPitchAngle = 0; camYawAngle = 0;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    glMatrixMode(GL_MODELVIEW);

    glPushMatrix();

    glRotatef(angle, 1, 0, 0);
    glRotatef(angle, 0, 1, 0);

    glColor3f(0, 1, 0);
    glutWireCube(150.0);

    glBegin(GL_LINES);
    glColor3f(1, 0, 0);
    for (int i = 0; i <= 75; i += 5)
    {
        glVertex3i(i, 0, 0);
        glVertex3i(-i, 0, 0);
        glVertex3i(0, i, 0);
        glVertex3i(0, -i, 0);
        glVertex3i(0, 0, i);
        glVertex3i(0, 0, -i);
    }
    glEnd();
    glPopMatrix();

    //RSHIFT and CTRL
    if (GetAsyncKeyState(VK_LSHIFT))
    {
        cam.slide(0, 1.0 * camMoveSpeed, 0);
    }
    if (GetAsyncKeyState(VK_LCONTROL))
    {
        cam.slide(0, -1.0 * camMoveSpeed, 0);
    }

    glutSwapBuffers();
}

void idleFunction()
{
    const double current_time = getTime();
    if ((current_time - last_render) > frame_delay)
    {
        last_render = current_time;
        glutPostRedisplay();
    }
}

void reshapeFunction(int w, int h)
{

}

void keyboardFunction(unsigned char key, int w, int h)
{
    switch (key)
    {
    case '+': case '=':
        speedRatio += 0.125;
        break;
    case '-': case '_':
        speedRatio -= 0.125;
        break;
    case 'A': case 'a':
        cam.slide(-1.0 * camMoveSpeed, 0, 0);
        break;
    case 'D': case 'd':
        cam.slide(1.0 * camMoveSpeed, 0, 0);
        break;
    case 'W': case 'w':
        cam.slide(0, 0, -1.0 * camMoveSpeed);
        break;
    case 'S': case 's':
        cam.slide(0, 0, 1.0 * camMoveSpeed);
        break;
    case 'Z': case 'z':
        cam.yaw(-1);
        break;
    case 'X': case 'x':
        cam.yaw(1);
        break;
    case 27:
        angle = 0;
        speedRatio = 0;
        cam.set(Point3(0, 0, 350), Point3(0, 0, 349), Vector3(0, 1, 0));
        break;
    default:
        cout << key << endl;
        break;
    }
}

void specialKeysFunction(int key, int x, int y)
{
    cout << key << endl;
}

void mouseFunc(int button, int state, int x, int y)
{
    if (button == GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    {
        mouseButtonWasPressed = true;
        lastMousePos.x = x;
        lastMousePos.y = y;
    }
}

void motionFunction(int mousePosX, int mousePosY)
{
    if (mousePosX >= 0 && mousePosX < windowWidth && mousePosY >= 0 && mousePosY < windowHeight)
    {
        if (mouseButtonWasPressed)
        {
            camPitchAngle += -mousePosY + lastMousePos.y;
            camYawAngle += mousePosX - lastMousePos.x;
            lastMousePos.x = mousePosX;
            lastMousePos.y = mousePosY;
        }
    }
}

int main(int argc, char* argv[])
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB);
    glutInitWindowSize(windowWidth, windowHeight);
    glutInitWindowPosition((GetSystemMetrics(SM_CXSCREEN) - windowWidth) / 2, (GetSystemMetrics(SM_CYSCREEN) - windowHeight) / 2);
    glutCreateWindow("Window");
    init();
    glutMainLoop();
    return 0;
}

Camera.h Camera.cpp

Answer 1

当你做的时候

glRotatef(angle, 1, 0, 0);
glRotatef(angle, 0, 1, 0);

然后模型绕y轴旋转然后旋转后的模型绕x轴旋转，因为glRotatef设置一个旋转矩阵并将其与当前矩阵相乘。
因为模型在绕 x 轴旋转之前绕 y 轴旋转，所以( View 空间)y 轴保持在 View 空间的 yz 平面。

如果你想保持 x 轴在 View 空间的 xz 平面内，你必须先绕 x 轴旋转:

glRotatef(angle, 0, 1, 0);
glRotatef(angle, 1, 0, 0);

---

当您将 pich() 和 yaw() 应用于相机对象时，会出现同样的问题。如果您切换它(先是 yaw()，然后是 pitch())，那么这不会解决问题，因为俯仰和偏航会随着每次鼠标移动而递增应用( pich(), yaw(), pich(), yaw(), pich() , 偏航() ...)。所以在 pitch() 之后总是有一个 yaw() 并且模型会倾斜。

要解决此问题，您必须总结 camPitchAngle 和 camYawAngle。考虑鼠标强度:

void motionFunction(int mousePosX, int mousePosY)
{
    if (mousePosX >= 0 && mousePosX < windowWidth && mousePosY >= 0 && mousePosY < windowHeight)
    {
        if (mouseButtonWasPressed)
        {
            camPitchAngle += (-mousePosY + lastMousePos.y) * mouseSensitivity;
            camYawAngle   += (mousePosX - lastMousePos.x) * mouseSensitivity;
            lastMousePos.x = mousePosX;
            lastMousePos.y = mousePosY;
        }
    }
}

在 displayFunction 中复制相机对象 (cam/curr_cam) 并应用 camPitchAngle 和 camYawAngle 到拷贝。使用拷贝设置 View 和投影矩阵:

void displayFunction()
{
    // [...]

    // cam.pitch(-(camPitchAngle *= mouseSensitivity)); <--- delete
    // cam.yaw(-(camYawAngle *= mouseSensitivity));     <--- delete

    // [...]

    Camera curr_cam = cam;
    curr_cam.yaw( -camYawAngle );
    curr_cam.pitch( -camPitchAngle );

    // [...]

    if (GetAsyncKeyState(VK_LSHIFT))
    {
        curr_cam.slide(0, 1.0 * camMoveSpeed, 0);
    }
    if (GetAsyncKeyState(VK_LCONTROL))
    {
        curr_cam.slide(0, -1.0 * camMoveSpeed, 0);
    }

    // [...]   
}    

当然你要分别设置camYawAngle = 0 camPitchAngle = 0; 当z, x或 ESC 被按下。