//Camera.C   Toby Jones March 2001
//This is a program that takes ketboard commands and allows a person to 
//fly around the world.
//All commands are outlined in the keyboard function

#include <GL/glut.h>
#include <GL/gl.h>
#include<GL/glu.h>
#include<stdlib.h>

//to enable where you are looking at and where you are going
//to be controlled by shperical coordinates
double theta = 3.141592654/2;
double phi = 0; 
double mag = 5;

//camera position
float px = 0;
float py = 0;
float pz = 5;

void init()
{
  glClearColor(0.0, 0.0, 0.0, 0.0);
  glShadeModel(GL_FLAT);
}

void Display()
{
  glClear(GL_COLOR_BUFFER_BIT);
  glColor3f(1.0, 1.0, 1.0);
  glLoadIdentity();
   
  //position, direction and orientation of the camera
  gluLookAt(px, py, pz,                      //camera position
	    px + mag*cos(theta)*cos(phi),    //looking at x
	    py+ mag*sin(phi) ,               //looking at y
	    pz - mag*sin(theta)*cos(phi),    //looking at z
	    0.0, 1.0, 0.0);                  //up direction
  
  //draw a cube
  glScalef(1.0, 1.0, 1.0);
  glutWireCube(1.0);
 
 glFlush();
}

void Keyboard (unsigned char key, int p, int o) {
  switch (key) {
    //temporary variable to allow moving right and left
    double temp1, temp2;
  case 'u':        //move straight up
    py +=1;
    glutPostRedisplay();
    break;
  case 'd':        //move straight down
    py -=1;
    glutPostRedisplay();
    break;
  case 'r':        //move directly right in respect to where you are
    px += sin(theta);
    pz += cos(theta);
    glutPostRedisplay();
    break;
  case 'l':         //move directly left in respect to where you are
    px -= sin(theta);
    pz -= cos(theta);
    glutPostRedisplay();
    break; 
  case 'b':         //move directly backward WRT where you're looking
    pz +=sin(theta)*cos(phi); 
    px -=cos(theta)*cos(phi); 
    py -=sin(phi);
    glutPostRedisplay();
    break;
  case 'f':         //move directly forward WRT where you're looking
    pz-= sin(theta)*cos(phi); 
    px +=cos(theta)*cos(phi); 
    py +=sin(phi);
    glutPostRedisplay();
    break;
  case 'L':         //Look left
    theta +=.1;
    glutPostRedisplay();
    break;
  case 'R':         //Look right
    theta -=.1;
    glutPostRedisplay();
    break;
  case 'U':         //Look up
    phi+=.1;
    glutPostRedisplay();
    break;
  case 'D':         //Look down
    phi-=.1;
    glutPostRedisplay();
    break;
  case 'Q':         //Quit 
  case 'q':
    exit (EXIT_SUCCESS);
  }
}
void reshape(int w, int h)
{
  //This is the important stuff. This allows the world to be projected like
  //you think it should. If you move the camera it changes the projections
  glViewport(0,0,(GLsizei) w, (GLsizei) h);      
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  //This call creates a window to project in of size(-x, x, -y, y, near, far) 
  glFrustum(-1.0, 1.0, -1.0, 1.0, 1.5, 20.0);
  glMatrixMode(GL_MODELVIEW);
}

//usual main
int main(int argc, char** argv)
{
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
  glutInitWindowSize(500, 500);
  glutInitWindowPosition(100, 100);
  glutCreateWindow(argv[0]);
  init();
  glutDisplayFunc(Display);
  glutReshapeFunc(reshape);
  glutKeyboardFunc (Keyboard);  
  glutMainLoop();
  return 0;
}