/* Rotates3D points. Changes points each time mouse is clicked (courtesy of Brooks van Horn) */
#ifdef _WIN32
#include <windows.h>
#endif
#include <GL/glut.h>
#include <stdlib.h>

void mouse( int, int, int, int );
void display( void );
void reshape( int, int );
void keyboard( unsigned char, int, int );
void Idle( void );
void InitializeVariables( void ); /// forwarding functions

int xdim, ydim; /// screen dimensions

struct vPoint
{
	inline float &operator[] ( int index ) 
	{
		return element[index];
	} 
	float element[3]; 
}; //

const float X_STEP = 0.005; 
const float Y_STEP = 0.020;
const float Z_STEP = 0.025; //

bool flag;                  /// flag to tell us if there is anything to draw yet/

vPoint rotation; // current rotation

const int MAX_DOTS = 10;   /// # of dots to generate and render/
vPoint dots[ MAX_DOTS ];   /// the set of points to render/

int main( int argc, char *argv[] )
{
	InitializeVariables(); /// nothing to do with OpenGL.  My function that zeroes variables and such stuff./

	xdim = ( argc > 1 ) ? atoi( argv[ 1 ] ) : 500;  ydim = ( argc > 2 ) ? atoi( argv[ 2 ] ) : 500;

	glutInit( &argc, argv ); //* Initialization function *//
	glutInitDisplayMode( GLUT_DOUBLE | GLUT_RGB ); /// Set double buffer and GRB modes/
	glutInitWindowSize( xdim, ydim ); /// Set the screen size/
	glutCreateWindow( "This is the title of the window.");
	glClearColor( 0.0, 0.0, 0.0, 0.0 ); /// clear color and alpha at each pixel/
	glShadeModel( GL_FLAT ); /// set shading mode to flat (constant color for each polygon)/
	glutDisplayFunc( display ); /// tells OpenGL what function to call when it needs to redraw/
	glutReshapeFunc( reshape ); /// tells OpenGL what function to call when window is reshaped/
	glutMouseFunc( mouse ); /// tells OpenGL what function to call when a mouse button is pressed/
	glutKeyboardFunc( keyboard ); /// tells OpenGL to call the keyboard function with current parameters/
	glutIdleFunc( Idle );
	glutMainLoop(); /// important call to include after the above 3/

	return EXIT_SUCCESS;
}

void InitializeVariables( void ) {rotation[ 0 ] = rotation[ 1 ] = rotation[ 2 ] = 0.0;  flag = true; }

void mouse( int button, int state, int x, int y )
	/* 
	button: GLUT_LEFT_BUTTON or GLUT_MIDDLE_BUTTON or GLUT_RIGHT_BUTTON,
	state : state of the button: pressed (GLUT_DOWN) or not pressed (GLUT_UP),
	x, y  : position of mouse 
	*/
{

if ( state == GLUT_UP ) return ; /// we don't care when the mouse button is released/

 for (int i = 0; i<MAX_DOTS; i++) for (int j = 0; j<3; j++) dots[i][j] = (float) rand() / (float) RAND_MAX; /// Generate dots/

 flag = false; /// we now have something to display/

glutPostRedisplay();} /// need to call display again so that a new thing is put on the screen/

 

void keyboard( unsigned char c, int x, int y )
//* c: ASCII character pressed (excluding shift, ctrl, alt), (x,y) = position of the mouse */
{ 
	if ( c == 27 ) exit( 0 );
}  // "escape" key

void Idle( void )
{
	rotation[0]+=X_STEP; rotation[1]+=Y_STEP; 
	rotation[2]+=Z_STEP; glutPostRedisplay();
}

void display( void )
{

 glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

 if( flag ) 
 {
	glutSwapBuffers();
	return;
 }
 glPushMatrix(); /// push matrix on stack/

 glColor3f( 1.0, 1.0, 1.0 ); /// Here I specify a color by giving R-G-B values from 0 to 1./
 glTranslatef( 0.0, 0.0, -3.0 ); /// move the dots so that we can see them/
 glRotatef(rotation[0],1,0,0);  glRotatef(rotation[1],0,1,0);
 glRotatef(rotation[2],0,0,1); /// rotate the dots/

 glBegin( GL_POINTS ); 

 for ( int i = 0; i < MAX_DOTS; i++ )
	glVertex3f(dots[i][0],dots[i][1],dots[i][2]);

 glEnd();

 glPopMatrix(); 
 glutSwapBuffers();
} /// This says: "DRAW WHAT YOU'VE GOT!"/

 

void reshape( int new_width, int new_height )
{
  xdim = new_width;  ydim = new_height;

  glViewport(0,0,(GLsizei) new_width, (GLsizei) new_height ); /// This resets the viewing port/
  glMatrixMode( GL_PROJECTION ); /// This resets the use of Matrices based upon the new view/
  glLoadIdentity();
  gluPerspective( 60.0, (GLfloat) xdim / (GLfloat) ydim, 0.1, 20.0 ); /// reset the viewing projection/
  glMatrixMode( GL_MODELVIEW );
}