/********************************************************************

  viewout.cpp - written by H. Masterman

  version 1.0 26 March 2003
  
  written to illustrate viewing and navigating.
  inside looking out

  ********************************************************************/

#include <stdlib.h>
#include <glut.h>
#include <math.h>
#define PI 3.141592653
	

GLfloat theta = 0.0, phi = 0.0;  //stores two angles
GLfloat radius = 1.0;
GLfloat xo = -10.0;
GLfloat yo = 0.0;
GLfloat zo = 0.0; // initial viewer position
GLfloat x,y,z; //point on viewing sphere

void display(void)
{
 

 glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //clear color buffer and z buffer
 
 glLoadIdentity();  // start with an identity in the MODELVIEW transformation

	x = radius * cos (theta) * cos (phi);
	y = radius * sin (theta);
	z = -radius * cos (theta)* sin(phi);

 
 gluLookAt(xo,yo,zo,xo+x,yo+y,zo+z,0,1,0);  //multiply viewing component of transformation


glutSolidTeapot(1.0);
glFlush();
glutSwapBuffers();
}
 
void spinCube()
{


}

void mouse(int btn, int state, int x, int y)
{
exit(0);
//exit the program on any mouse click
}

void special (int key_pressed, int mouse_x, int mouse_y)
{
	if (key_pressed == GLUT_KEY_LEFT)  //turn left
	{
		phi += 0.1;  //radians
		glutPostRedisplay();
		return;
	}
	if (key_pressed == GLUT_KEY_RIGHT)  //turn right
	{
		phi -= 0.1;  //radians
		glutPostRedisplay();
		return;
	}
	if (key_pressed == GLUT_KEY_UP)  //look up
	{
		if (theta < (PI/2 - 0.1)) theta += 0.1;
		glutPostRedisplay();
		return;
	}
	if (key_pressed == GLUT_KEY_DOWN)  //look down
	{
		 if (theta > (-PI/2 + 0.1)) theta -= 0.1;
		glutPostRedisplay();
		return;
	}

	if (key_pressed == GLUT_KEY_PAGE_UP)  //walk ahead
	{
		xo+=x;
		zo+=z;
		glutPostRedisplay();
		return;
	}

	if (key_pressed == GLUT_KEY_PAGE_DOWN)  //walk backward
	{
		xo-=x;
		zo-=z;
		glutPostRedisplay();
		return;
	}
}

void myReshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
	gluPerspective(60.0, 1.0,1.0,30.0);  //for perspective viewing
    glMatrixMode(GL_MODELVIEW);
	
}

void
main(int argc, char **argv)
{
    glutInit(&argc, argv);

/* need both double buffering and z buffer */

    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB |GLUT_DEPTH);
    glutInitWindowSize(700, 700);
    glutCreateWindow("Viewing Example: Outside In");
    glutReshapeFunc(myReshape);
    glutDisplayFunc(display);
	glutMouseFunc(mouse);
	glutSpecialFunc(special);
	glEnable(GL_DEPTH_TEST); /* Enable hidden--surface--removal */
	glEnable(GL_LIGHT0);
	glEnable(GL_LIGHTING);
    glutMainLoop();
}