////////////////////////////////////////////////////////////////////////////////////////////
// bezierCurves.cpp
// 
// This program shows Bezier curves of orders 2 to 6, where each control point can be moved.
// Also drawn is the control polygon.
//
// Interaction:
// Press the up/down arrows to select an order and press enter.
// Press space to select a control point. 
// Press the arrow keys to move the selected control point.
// Press delete to reset.
//
// Sumanta Guha
////////////////////////////////////////////////////////////////////////////////////////////

#include <iostream>

#ifdef __APPLE__
#  include <GLUT/glut.h>
#else
#  include <GL/glut.h>
#endif

using namespace std;

// Begin globals.
static int numVal = 0, order = 2, askOrder = 1;
static long font = (long)GLUT_BITMAP_8_BY_13; // Font selection.

// Control points.
static float controlPoints[6][3] = 
{
	{ -40.0, 0.0, 0.0}, { -30.0, 0.0, 0.0}, { -10.0, 0.0, 0.0},
	{0.0, 0.0, 0.0}, {30.0, 0.0, 0.0}, { 40.0, 0.0, 0.0}
};

// Control point values stored unchanged for use on reset.
static float originalControlPoints[6][3] = 
{
	{ -40.0, 0.0, 0.0}, { -30.0, 0.0, 0.0}, { -10.0, 0.0, 0.0},
	{0.0, 0.0, 0.0}, {30.0, 0.0, 0.0}, { 40.0, 0.0, 0.0}
};
// End globals.

// Initialization routine.
void setup(void)
{
   glClearColor(1.0, 1.0, 1.0, 0.0);
}

// Routine to restore control points to original values.
void restoreControlPoints(void)
{
   int i, j;
   for (i=0; i<6; i++)
      for (j=0; j<3; j++)
         controlPoints[i][j] = originalControlPoints[i][j];
}

// Routine to draw a bitmap character string.
void writeBitmapString(void *font, char *string)
{  
   char *c;

   for (c = string; *c != '\0'; c++) glutBitmapCharacter(font, *c);
}

// Drawing routine.
void drawScene(void)
{
   glClear(GL_COLOR_BUFFER_BIT);
   glColor3f(0.0, 0.0, 0.0);

   if (askOrder == 1)
   // First screen.
   {
	  glColor3f(0.0, 0.0, 0.0);
	  glRasterPos3f(-25.0, 0.0, 0.0);
      writeBitmapString((void*)font, "Show Bezier curve of order: ");

	  glColor3f(1.0, 0.0, 0.0);
	  glRasterPos3f(20.0, 0.0, 0.0);
	  switch (order) 
	  {
	     case 2:
	        writeBitmapString((void*)font, "2");
		    break;
		 case 3:
			writeBitmapString((void*)font, "3");
		    break;
		 case 4:
			writeBitmapString((void*)font, "4");
		    break;
		 case 5:
			writeBitmapString((void*)font, "5");
		    break;
		 case 6:
			writeBitmapString((void*)font, "6");
		    break;
		 default:
	        break;
	  }
   }
   else
   // Second screen.
   {
      int i;

	  // Draw the control polygon in light gray.
	  glColor3f(0.7, 0.7, 0.7);
	  glBegin(GL_LINE_STRIP);
	  for (i = 0; i < order; i++) 
	     glVertex3fv(controlPoints[i]);
	  glEnd();

      // Specify and enable the Bezier curve.
	  glMap1f(GL_MAP1_VERTEX_3, 0.0, 1.0, 3, order, &controlPoints[0][0]);
	  glEnable(GL_MAP1_VERTEX_3);

	  // Draw the Bezier curve by defining a sample grid and evaluating on it.
	  glColor3f(0.0, 0.0, 0.0);
	  glMapGrid1f(100, 0.0, 1.0);
	  glEvalMesh1(GL_LINE, 0, 100);

	  // Draw the control points as dots.
	  glPointSize(5.0);
      glColor3f(0.0, 1.0, 0.0);	  
	  glBegin(GL_POINTS);
	  for (i = 0; i < order; i++) 
	     glVertex3fv(controlPoints[i]);
	  glEnd();

	  // Highlight selected control point,
	  glColor3f(1.0, 0.0, 0.0);
	  glBegin(GL_POINTS);
	     glVertex3fv(controlPoints[numVal]);     
	  glEnd();
   }
   glutSwapBuffers();
}

// OpenGL window reshape routine.
void resize(int w, int h)
{
   glViewport(0, 0, (GLsizei)w, (GLsizei)h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   glOrtho(-50.0, 50.0, -50.0, 50.0, -1.0, 1.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}

// Keyboard input processing routine.
void keyInput(unsigned char key, int x, int y)
{
   switch (key) 
   {
      case 27:	
         exit(0);
         break;
      case 13:	
         askOrder = 0;
	     glutPostRedisplay();
         break;
      case 127:	
         askOrder = 1; 
	     order = 2;
	     restoreControlPoints();
	     glutPostRedisplay();
         break;
      case ' ':
	     if (askOrder == 0)
		 {
		    if (numVal < order-1) numVal++;
		    else numVal = 0;
		 }
         glutPostRedisplay();
         break;
      default:
         break;
   }
}

// Callback routine for non-ASCII key entry.
void specialKeyInput(int key, int x, int y)
{
   if(key == GLUT_KEY_UP)
   {
      if (askOrder == 1) 
	  {
	     if (order < 6) order += 1;
	  }
	  else
         controlPoints[numVal][1] += 1.0;
   }
   if(key == GLUT_KEY_DOWN)
   {
      if (askOrder == 1) 
	  {
	     if (order > 2) order -= 1;
	  }
	  else
	     controlPoints[numVal][1] -= 1.0;
   }
   if(key == GLUT_KEY_LEFT) controlPoints[numVal][0] -= 1.0;
   if(key == GLUT_KEY_RIGHT) controlPoints[numVal][0] += 1.0;
	
   glutPostRedisplay();
}

// Routine to output interaction instructions to the C++ window.
void printInteraction(void)
{
   cout << "Interaction:" << endl;
   cout << "Press the up/down arrows to select an order and press enter." << endl
        << "Press space to select a control point." << endl 
        << "Press the arrow keys to move the selected control point." << endl
        << "Press delete to reset." << endl;
}

// Main routine.
int main(int argc, char **argv) 
{
   printInteraction();
   glutInit(&argc, argv);
   glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB); 
   glutInitWindowSize(500, 500);
   glutInitWindowPosition(100, 100); 
   glutCreateWindow("bezierCurves.cpp");
   setup(); 
   glutDisplayFunc(drawScene); 
   glutReshapeFunc(resize);  
   glutKeyboardFunc(keyInput);
   glutSpecialFunc(specialKeyInput);
   glutMainLoop(); 

   return 0;  
}