我已经从教程等在线使用 OpenGL 和 C++ 组装了一个第三人称相机系统，但我似乎无法找出具体问题。当我使用鼠标移动转动时，我的角色围绕相机旋转，而不是相机围绕角色旋转并且角色原地转动。我应该怎么做才能让角色原地转身？
// variables ..
void checkMouse(){
if (mouseXPos > SCREEN_WIDTH/2){
// turn right
yrot += abs(mouseXPos - SCREEN_WIDTH/2) * .005;
} else if (mouseXPos < SCREEN_WIDTH/2){
// turn left
yrot -= abs(mouseXPos - SCREEN_WIDTH/2) * .005;
}
if (mouseYPos > SCREEN_HEIGHT/2){
// look up
xrot += abs(mouseYPos - SCREEN_HEIGHT/2) * .005;
} else if (mouseYPos < SCREEN_HEIGHT/2){
// look down
xrot -= abs(mouseYPos - SCREEN_HEIGHT/2) * .005;
}
}
void checkKeys(){
if(keys['t'] == true){
wireframe=!wireframe;
if(wireframe){
glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
}
else glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
}
if (keys['w'] == true){
float xrotrad, yrotrad;
yrotrad = (yrot / 180 * 3.141592654f);
xrotrad = (xrot / 180 * 3.141592654f);
xpos += float(sin(yrotrad)) * 10 ;
zpos -= float(cos(yrotrad)) * 10 ;
}
if (keys['s'] == true){
float xrotrad, yrotrad;
yrotrad = (yrot / 180 * 3.141592654f);
xrotrad = (xrot / 180 * 3.141592654f);
xpos -= float(sin(yrotrad)) * 10;
zpos += float(cos(yrotrad)) * 10;
}
if (keys['a'] == true){
float yrotrad;
yrotrad = (yrot / 180 * 3.141592654f);
xpos -= float(cos(yrotrad)) * 10;
zpos -= float(sin(yrotrad)) * 10;
}
if (keys['d'] == true){
float yrotrad;
yrotrad = (yrot / 180 * 3.141592654f);
xpos += float(cos(yrotrad)) * 10;
zpos += float(sin(yrotrad)) * 10;
}
}
void renderScene(){
// Clear framebuffer & depth buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
// Reset Modelview matrix
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
// Set view position & direction
gluLookAt(0,0,5, 0,0,-1, 0,1,0);
checkKeys();
checkMouse();
// 3rd person object
// draw body
glPushMatrix();
glRotatef(xrot,1.0,0.0,0.0); // keeps object on ground level rather than always in front of camera
glTranslatef(0,-90,-400.0); // keep object 400 away from camera
glRotatef(-90,0.0,1.0,0.0);
glutSolidCube(20);
glPopMatrix();
// CAMERA
glRotatef(xrot,1.0,0.0,0.0); //rotate our camera on the x-axis (left and right)
glRotatef(yrot,0.0,1.0,0.0); //rotate our camera on the y-axis (up and down)
glTranslated(-xpos,-ypos-200,-zpos);
// rest of world
glPushMatrix();
glutSolidCube(30);
glPopMatrix();
// ..
glDisable(GL_TEXTURE_2D);
// Swap double buffer for flicker-free animation
glutSwapBuffers();
}
void updateScene(){
// Wait until at least 16ms passed since start of last frame
// Effectively caps framerate at ~60fps
while(timeGetTime()-lastTickCount<16);
lastTickCount=timeGetTime();
// Draw the next frame
glutPostRedisplay();
}
void keypress (unsigned char key, int x, int y) {
keys[key] = true;
// Test if user pressed ESCAPE (ascii 27)
// If so, exit the program
if(key==27){
exitScene();
}
}
void keypressup (unsigned char key, int x, int y) {
keys[key] = false;
wheel_turn = 0;
}
void mouseMovement(int x, int y) {
mouseXPos = x;
mouseYPos = y;
}
void mouseClick(int button, int state, int x, int y){
if (button == GLUT_LEFT_BUTTON){
if (state == GLUT_DOWN)
lButton = true;
else
lButton = false;
}
}
void setupScene(){
forwards = 0;
strafe = 0;
turn = 0;
std::cout<<"Initializing scene..."<<std::endl;
//Set up Lighting Stuff
glLightfv(GL_LIGHT0, GL_POSITION, left_light_position);
glLightfv(GL_LIGHT0, GL_AMBIENT, white_light);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glLightfv(GL_LIGHT0, GL_DIFFUSE, white_light);
glShadeModel(GL_SMOOTH);
glEnable(GL_DEPTH_TEST);
}
void exitScene(){
std::cout<<"Exiting scene..."<<std::endl;
// Close window
glutDestroyWindow(windowId);
// Free any allocated memory
// Exit program
exit(0);
}
void setViewport(int width, int height) {
// Work out window ratio, avoid divide-by-zero
if(height==0)height=1;
float ratio = float(width)/float(height);
// Reset projection matrix
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
// Fill screen with viewport
glViewport(0, 0, width, height);
// Set a 45 degree perspective
gluPerspective(45, ratio, .1, 200000);
}
int main(int argc, char *argv[]){
// Initialise OpenGL
glutInit(&argc, argv);
// Set window position, size & create window
glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH);
glutInitWindowPosition(50,50);
glutInitWindowSize(SCREEN_WIDTH,SCREEN_HEIGHT);
windowId = glutCreateWindow("3rd person cam");
// Set GLUT callback functions
glutReshapeFunc(setViewport);
glutDisplayFunc(renderScene);
glutIdleFunc(updateScene);
glutKeyboardFunc(keypress);
glutKeyboardUpFunc(keypressup);
glutPassiveMotionFunc(mouseMovement); //check for mouse movement
glutMotionFunc(mouseMovement);
glutMouseFunc(mouseClick);
// Setup OpenGL state & scene resources (models, textures etc)
setupScene();
// Show window & start update loop
glutMainLoop();
return 0;
}