/*    PICKING LAB	*/



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

// function prototypes
void display(void);
void reshape(int width, int height);
void keyboard(unsigned char key, int x, int y);
void mouse(int button, int state, int x, int y);
void motion(int x, int y);
void init(void);



// global vars



// viewpoint
double theta=.5, phi=.5, d=30;

// window
int width = 400;
int height = 400;


using namespace std;


int 
main(int argc, char **argv)
{

  // set up window
  glutInitWindowSize(400, 400);
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
  glutCreateWindow("Picking Big Objects Lab");

  // register callback functions
  glutDisplayFunc(display);
  glutReshapeFunc(reshape); 
  glutKeyboardFunc(keyboard);
  glutMotionFunc(motion);
  glutMouseFunc(mouse);


  // initalize opengl parameters
  init();



  // loop until something happens
  glutMainLoop();
  return 0;           
}

void init()
{
	
  // initialize viewing system
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(45.0, 1.0, 0.5, 100.0);
  glMatrixMode(GL_MODELVIEW);

  // shading model
  glEnable(GL_SMOOTH);
 

  // initialize background color to black
  glClearColor(0.0,0.0,0.0,0.0);

  // enable depth buffering
  glEnable(GL_DEPTH_TEST);

}



void reshape(int newWidth, int newHeight)
{
	width = newWidth;
	height = newHeight;
	// preserve aspect ratio
	if (width < height)
		glViewport(0,0,width,width);
	else
		glViewport(0,0,height,height);
}

void display()
{
	// we'll draw axis lines centered at (0,0,0)
	double center[3]={0,0,0};

	// compute eye position
	// the eye is a distance d from the center at
	// at an angle phi from z in plane y=1
	// and then rotate the theta out of the y=1 plane
	// e.g. when the center is (0,0,0) and phi=theta=0 we are at (0,0,d)
	// looking at the origin

	glLoadIdentity();
	double eye[3]={0,0,0};
	eye[0] = center[0] + (float) d * cos(theta) * sin(phi);
	eye[1] = center[1] + (float) d * sin(theta);
	eye[2] = center[2] + (float) d * cos(theta) * cos(phi);

	// compute up vector
	// we use (0,1,0) as the default up position
	// this doesn't work if the eye is on the y-axis
	// but we just won't let the user do that
	double up[3]={0,1,0};

	gluLookAt(eye[0],eye[1],eye[2], center[0],center[1],center[2],up[0], up[1], up[2]);


	// clear buffers
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

	glColor3f(1,0,0);
	glBegin(GL_TRIANGLES);
	glVertex3f(0,0,0);
	glVertex3f(5,0,0);
	glVertex3f(2.5,5,0);

	glColor3f(0,0,1);
	glBegin(GL_TRIANGLES);
	glVertex3f(0,0,-5);
	glVertex3f(10,0,-5);
	glVertex3f(5,10,-5);
	glEnd();


	// draw to screen
	glutSwapBuffers();
}

void keyboard(unsigned char key, int mouseX, int mouseY)
{

	switch (key) {

		case 'h':
			cout << "Use i to zoom in." << endl;
			cout << "Use o to zoom in." << endl;
			break;
		case 'i':
			d-=5;
			break;
		case 'o':
			d+=5;
			break;



	}
	glutPostRedisplay();
}




/*
*	This routine reads mouse movement and adjusts
*	camera position/orientation.
*/

void motion(int x, int y)
{

	static int currX=-1;
	static int currY=-1;

	// wait until a mouse position is recorded and
	// avoid really big jumps
	if (currX>0  && abs(x-currX) < width/6 && abs(y-currY) < height/6) {
		
		//update phi and theta based on change in x and y
		int xChange = currX - x;
		int yChange = y - currY;
		phi += (xChange / 180.0);
		theta += (yChange / 180.0);
		
		// limit theta to -4pi/9 and 4pi/9
		// it is disorienting to lose "up"
		if (theta < -4*3.14159/9.0)
			theta = -4*3.14159/9.0;
		if (theta > 4*3.14159/9.0)
			theta = 4*3.14159/9.0;
	}
	currX = x;
	currY = y;
	glutPostRedisplay();
}



void mouse(int button, int state, int x, int y)
{

	}