在第一人稱視角和第三人稱視角（OpenGL）之間切換

Question

我正在嘗試實現一個機器人可以走動的簡單3D環境。 我希望用戶能夠在機器人的第一人稱視角和第三人稱視角之間切換。

我已經實現了機器人以及一個帶有其他一些對象的簡單區域。 當前，該視圖是第三人稱。 我一直在使用gluPerspective函數嘗試實現人頭轉動時已經轉過頭的第一人（已經實現了頭轉彎），但是無論我使用什么參數，似乎都無法進行切換。 它始終保持不變。 有沒有比我到目前為止嘗試過的方法更簡單的方法來達到這種效果？ 是因為我的方法而沒有做的工作嗎？

下面的代碼足以將透視圖設置為第一人稱視角，但是它並不符合我的期望。 我可以在他上面初始化它，但是我不確定如何使機器人隨相機移動，因為風景有效地圍繞着他移動。 我當時想我可以通過在第一人稱視角時移開機器人來“假裝”這種東西。 有什么想法嗎？ ：

glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
double atx = xPos + cos(lookAngle);
double atz = zPos + sin(lookAngle);
double atHeight = eyeHeight + eyeIncline;
gluLookAt(xPos, eyeHeight, zPos, atx, atHeight, atz, 0.0, 1.0, 0.0);

我嘗試在鍵盤功能中調用switch語句以切換到第三人稱。 鍵盤調用如下所示：

void key(unsigned char k, int x, int y)
{
if ( k == 27 ) /* Escape */
  exit(0);
else if ( k == 86 ) { /* 'v' for view change */
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
   gluLookAt(0, 0, -20, 0, 0, -1, 0, 1, 0); //Look down z-axis

}
glutPostRedisplay();
}

但這是行不通的。 沒有切換。

代碼如下：

#define GLUT_DISABLE_ATEXIT_HACK

#include <GL/glut.h>
#include <GL/gl.h>
#include <math.h>

#define TORSO_HEIGHT 5.0
#define UPPER_ARM_HEIGHT 3.0
#define LOWER_ARM_HEIGHT 2.0
#define UPPER_LEG_RADIUS  0.5
#define LOWER_LEG_RADIUS  0.5
#define LOWER_LEG_HEIGHT 2.0
#define UPPER_LEG_HEIGHT 3.0
#define UPPER_LEG_RADIUS  0.5
#define TORSO_RADIUS 1.0
#define UPPER_ARM_RADIUS  0.5
#define LOWER_ARM_RADIUS  0.5
#define HEAD_HEIGHT 1.5
#define HEAD_RADIUS 1.0

double cubeX[] = { 5.0, 5.0, 5.0 };
double cubeY[] = { 3.0, 3.0, 3.0 };
double cubeZ[] = { 7.0, 5.0, 3.0 };
double cubeR[] = { 1.0, 0.0, 0.0 };
double cubeG[] = { 0.0, 1.0, 0.0 };
double cubeB[] = { 0.0, 0.0, 1.0 };

double xPos = 2.0, zPos = 5.0;
double eyeHeight = 4.5;
double eyeIncline = -0.5;
double lookAngle = 0.0; //In rads

double posIncr = 0.25;
double thetaIncr = 0.1;

typedef float point[3];

static GLfloat theta[11] = {0.0,0.0,0.0,0.0,0.0,0.0,0.0,
        180.0,0.0,180.0,0.0}; /* initial joint angles */
static GLint angle = 2;

GLUquadricObj *t, *h, *lua, *lla, *rua, *rla, *lll, *rll, *rul, *lul, *lf1, *lf2;

double size=1.0;

void torso()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(t,TORSO_RADIUS, TORSO_RADIUS, TORSO_HEIGHT,10,10);
glPopMatrix();
}

void head()
{
glPushMatrix();
glTranslatef(0.0, 0.5*HEAD_HEIGHT,0.0);
glScalef(HEAD_RADIUS, HEAD_HEIGHT, HEAD_RADIUS);
gluSphere(h,1.0,10,10);
glPopMatrix();
}

void left_upper_arm()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(lua,UPPER_ARM_RADIUS, UPPER_ARM_RADIUS, UPPER_ARM_HEIGHT,10,10);
glPopMatrix();
}

void left_lower_arm()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(lla,LOWER_ARM_RADIUS, LOWER_ARM_RADIUS, LOWER_ARM_HEIGHT,10,10);
glPopMatrix();
}

void left_finger1()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(lf1,FINGER_1_RADIUS, FINGER_1_RADIUS, FINGER_1_HEIGHT,10,10);
glPopMatrix();
}

void left_finger2()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(lla,LOWER_ARM_RADIUS, LOWER_ARM_RADIUS, LOWER_ARM_HEIGHT,10,10);
glPopMatrix();
} 

void right_upper_arm()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(rua,UPPER_ARM_RADIUS, UPPER_ARM_RADIUS, UPPER_ARM_HEIGHT,10,10);
glPopMatrix();
}

void right_lower_arm()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(rla,LOWER_ARM_RADIUS, LOWER_ARM_RADIUS, LOWER_ARM_HEIGHT,10,10);
glPopMatrix();
}

void left_upper_leg()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(lul,UPPER_LEG_RADIUS, UPPER_LEG_RADIUS, UPPER_LEG_HEIGHT,10,10);
glPopMatrix();
}

void left_lower_leg()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(lll,LOWER_LEG_RADIUS, LOWER_LEG_RADIUS, LOWER_LEG_HEIGHT,10,10);
glPopMatrix();
}

void right_upper_leg()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(rul,UPPER_LEG_RADIUS, UPPER_LEG_RADIUS, UPPER_LEG_HEIGHT,10,10);
glPopMatrix();
}

void right_lower_leg()
{
glPushMatrix();
glRotatef(-90.0, 1.0, 0.0, 0.0);
gluCylinder(rll,LOWER_LEG_RADIUS, LOWER_LEG_RADIUS, LOWER_LEG_HEIGHT,10,10);
glPopMatrix();
}

void drawCube( int i )
{
double x = cubeX[i];
double y = cubeY[i];
double z = cubeZ[i];

glColor3i(1, 0, 0); //Red cube
glPushMatrix();
glTranslatef(x,y,z);
glutSolidCube(1);
glPopMatrix();

glColor3i(0, 1, 0); //Green Cube
glPushMatrix();
glTranslatef(x,y,z);
glutSolidCube(1);
glPopMatrix();

glColor3i(0, 0, 1); //Blue Cube
glPushMatrix();
glTranslatef(x,y,z);
glutSolidCube(1);
glPopMatrix();

glColor3i(0, 1, 1);
glPushMatrix();
glTranslatef(x,y,z);
glutSolidCube(1);
glPopMatrix();

}

void drawCubes(void)
{

glLoadName(1);
drawCube(0);

glLoadName(2);
drawCube(1);

glLoadName(3);
drawCube(2);

/* Set name back to '0' to indicate background. */
glLoadName(0);
}

void drawFloor(void)
{
GLfloat mat_diffuse[] = { 0.5, 0.5, 0.5, 1.0 };
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
glBegin(GL_POLYGON);
  glNormal3f(0.0, 1.0, 0.0);
  glVertex3f(-10.0, 0.0, -10.0);
  glVertex3f(10.0, 0.0, -10.0);
  glVertex3f(10.0, 0.0,  10.0);
  glVertex3f(-10.0, 0.0,  10.0);
glEnd();
}

void doDrawing(void)
{

drawCubes();

drawFloor();

/* Everything else is a lighter shade of grey. */
GLfloat mat_diffuse[] = { 0.8, 0.8, 0.8, 1.0 };
glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
}

void drawEnviro(void)
{
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
double atx = xPos + cos(lookAngle);
double atz = zPos + sin(lookAngle);
double atHeight = eyeHeight + eyeIncline;
gluLookAt(xPos, eyeHeight, zPos, atx, atHeight, atz, 0.0, 1.0, 0.0);

glPushMatrix();
doDrawing();
glPopMatrix();
}

void display(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
drawEnviro();
glLoadIdentity();
gluLookAt(0, 0, -20, 0, 0, -1, 0, 1, 0);
glColor3f(0.0, 0.0, 0.0);

glRotatef(theta[0], 0.0, 1.0, 0.0);
torso();
glPushMatrix();

glTranslatef(0.0, TORSO_HEIGHT+0.5*HEAD_HEIGHT, 0.0);
glRotatef(theta[1], 1.0, 0.0, 0.0);
glRotatef(theta[2], 0.0, 1.0, 0.0);
glTranslatef(0.0, -0.5*HEAD_HEIGHT, 0.0);
head();

glPopMatrix();
glPushMatrix();
glTranslatef(-(TORSO_RADIUS + UPPER_ARM_RADIUS), 0.9 * TORSO_HEIGHT, 0.0);
glRotatef(theta[3], 1.0, 0.0, 0.0);
left_upper_arm();

glTranslatef(0.0, UPPER_ARM_HEIGHT, 0.0);
glRotatef(theta[4], 1.0, 0.0, 0.0);
left_lower_arm();

glTranslatef(0.0, LOWER_ARM_HEIGHT, 0.0);
glRotatef(theta[11], 1.0, 0.0, 0.0);
left_finger1();

glPopMatrix();
glPushMatrix();
glTranslatef(TORSO_RADIUS+UPPER_ARM_RADIUS, 0.9*TORSO_HEIGHT, 0.0);
glRotatef(theta[5], 1.0, 0.0, 0.0);
right_upper_arm();

glTranslatef(0.0, UPPER_ARM_HEIGHT, 0.0);
glRotatef(theta[6], 1.0, 0.0, 0.0);
right_lower_arm();

glPopMatrix();
glPushMatrix();
glTranslatef(-(TORSO_RADIUS+UPPER_LEG_RADIUS), 0.1*UPPER_LEG_HEIGHT, 0.0);
glRotatef(theta[7], 1.0, 0.0, 0.0);
left_upper_leg();

glTranslatef(0.0, UPPER_LEG_HEIGHT, 0.0);
glRotatef(theta[8], 1.0, 0.0, 0.0);
left_lower_leg();

glPopMatrix();
glPushMatrix();
glTranslatef(TORSO_RADIUS+UPPER_LEG_RADIUS, 0.1*UPPER_LEG_HEIGHT, 0.0);
glRotatef(theta[9], 1.0, 0.0, 0.0);
right_upper_leg();

glTranslatef(0.0, UPPER_LEG_HEIGHT, 0.0);
glRotatef(theta[10], 1.0, 0.0, 0.0);
right_lower_leg();

glPopMatrix();

glFlush();
glutSwapBuffers();
}

void setProjection(void)
{
gluPerspective(60.0, 1.0, 0.1, 100.0);
}

void mouse(int btn, int state, int x, int y)
{
  if(btn==GLUT_LEFT_BUTTON && state == GLUT_DOWN)
    {
    theta[angle] += 5.0;
    if( theta[angle] > 360.0 ) theta[angle] -= 360.0;
    }
  if(btn==GLUT_RIGHT_BUTTON && state == GLUT_DOWN)
    {
    theta[angle] -= 5.0;
    if( theta[angle] < 360.0 ) theta[angle] += 360.0;
    }
    display();
 }

void menu(int id)
{
if (id < 11 ) angle = id;
if (id == 11 ) exit(0);
}

void specialKey(int k, int x, int y)
{
/* Accept commands to move the viewpoint. */
switch (k) {
  case GLUT_KEY_UP:
     xPos += posIncr * cos(lookAngle);
     zPos += posIncr * sin(lookAngle);
     break;
  case GLUT_KEY_DOWN:
     xPos -= posIncr * cos(lookAngle);
     zPos -= posIncr * sin(lookAngle);
     break;
  case GLUT_KEY_LEFT:
     lookAngle -= thetaIncr;
     break;
  case GLUT_KEY_RIGHT:
     lookAngle += thetaIncr;
     break;
  case GLUT_KEY_PAGE_UP:
     eyeIncline += 0.5;
     break;
  case GLUT_KEY_PAGE_DOWN:
     eyeIncline -= 0.5;
     break;
  case GLUT_KEY_HOME:
     eyeHeight += 0.5;
     break;
  case GLUT_KEY_END:
     eyeHeight -= 0.5;
     break;
  default:
     return;
  }
  glutPostRedisplay();
 }

void reshape(int w, int h) 
{
glViewport(0, 0, w, h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective (65.0, w/h, 1, 1000.0);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}

void init()
{
    GLfloat mat_specular[]={1.0, 1.0, 1.0, 1.0};
    GLfloat mat_diffuse[]={1.0, 1.0, 1.0, 1.0};
    GLfloat mat_ambient[]={1.0, 1.0, 1.0, 1.0};
    GLfloat mat_shininess={100.0};
    GLfloat light_ambient[]={0.0, 0.0, 0.0, 1.0};
    GLfloat light_diffuse[]={1.0, 1.0, 1.0, 1.0};
    GLfloat light_specular[]={1.0, 1.0, 1.0, 1.0};
    GLfloat light_position[]={10.0, 10.0, 10.0, 0.0};

    glLightfv(GL_LIGHT0, GL_POSITION, light_position);
    glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
    glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
    glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);

    glMaterialfv(GL_FRONT, GL_SPECULAR, mat_specular);
    glMaterialfv(GL_FRONT, GL_AMBIENT, mat_ambient);
    glMaterialfv(GL_FRONT, GL_DIFFUSE, mat_diffuse);
    glMaterialf(GL_FRONT, GL_SHININESS, mat_shininess);

    glShadeModel(GL_SMOOTH);
    glEnable(GL_LIGHTING);
    glEnable(GL_LIGHT0);
    glDepthFunc(GL_LEQUAL);
    glEnable(GL_DEPTH_TEST);

    glClearColor(0.0, 0.0, 0.0, 0.0);
    glMatrixMode(GL_PROJECTION);

    glLoadIdentity();
    setProjection();

    //Fill the body parts of the robot
    h=gluNewQuadric();
    gluQuadricDrawStyle(h, GLU_FILL);
    t=gluNewQuadric();
    gluQuadricDrawStyle(t, GLU_FILL);
    lua=gluNewQuadric();
    gluQuadricDrawStyle(lua, GLU_FILL);
    lla=gluNewQuadric();
    gluQuadricDrawStyle(lla, GLU_FILL);
    rua=gluNewQuadric();
    gluQuadricDrawStyle(rua, GLU_FILL);
    rla=gluNewQuadric();
    gluQuadricDrawStyle(rla, GLU_FILL);
    lul=gluNewQuadric();
    gluQuadricDrawStyle(lul, GLU_FILL);
    lll=gluNewQuadric();
    gluQuadricDrawStyle(lll, GLU_FILL);
    rul=gluNewQuadric();
    gluQuadricDrawStyle(rul, GLU_FILL);
    rll=gluNewQuadric();
    gluQuadricDrawStyle(rll, GLU_FILL);
    lf1=gluNewQuadric();
    gluQuadricDrawStyle(lf1, GLU_FILL);

 }

int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
glutInitWindowSize(500, 500);
glutCreateWindow("robot");
init();
glutReshapeFunc(reshape);
glutDisplayFunc(display);
glutMouseFunc(mouse);
glutSpecialFunc(specialKey);

glutCreateMenu(menu);
glutAddMenuEntry("torso", 0);
glutAddMenuEntry("head1", 1);
glutAddMenuEntry("head2", 2);
glutAddMenuEntry("right_upper_arm", 3);
glutAddMenuEntry("right_lower_arm", 4);
glutAddMenuEntry("left_upper_arm", 5);
glutAddMenuEntry("left_lower_arm", 6);
glutAddMenuEntry("right_upper_leg", 7);
glutAddMenuEntry("right_lower_leg", 8);
glutAddMenuEntry("left_upper_leg", 9);
glutAddMenuEntry("left_lower_leg", 10);
glutAddMenuEntry("quit", 11);
glutAttachMenu(GLUT_MIDDLE_BUTTON);

glutMainLoop();

return 0;
}

Answer 1

就像所有與繪圖相關的東西一樣，在您的案例display ，設置投影矩陣（以及設置視口和模型視圖矩陣）都屬於繪圖代碼路徑。 不要將其reshape 。 init是完全錯誤的。