////////////////////////////////////////////////////////////////////////////////////         
// bezierSurface.cpp
//
// This program allows the user to design a Bezier surface by moving control points.
// Also drawn is the control polyghedron.
//
// Interaction:
// Press space and tab to select a control point.
// Press the right/left arrow keys to move the control point up/down the x-axis.
// Press the up/down arrow keys to move the control point up/down the y-axis.
// Press the page up/down keys to move the control point up/down the z-axis.
// Press the x, X, y, Y, z, Z keys to rotate the viewpoint.
//
//Sumanta Guha.
//////////////////////////////////////////////////////////////////////////////////// 

#include <iostream>

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

using namespace std;

// Begin globals.
// Initial control points.
static float controlPoints[6][4][3] = 
{
	{{-3.0, 0.0, 5.0}, {-0.25, 0.0, 5.0}, {0.25, 0.0, 5.0}, {3.0, 0.0, 5.0}},
	{{-3.0, 0.0, 3.0}, {-0.25, 0.0, 3.0}, {0.25, 0.0, 3.0}, {3.0, 0.0, 3.0}},
	{{-3.0, 0.0, 1.0}, {-0.25, 0.0, 1.0}, {0.25, 0.0, 1.0}, {3.0, 0.0, 1.0}},
	{{-3.0, 0.0, -1.0}, {-0.25, 0.0, -1.0}, {0.25, 0.0, -1.0}, {3.0, 0.0, -1.0}},
	{{-3.0, 0.0, -3.0}, {-0.25, 0.0, -3.0}, {0.25, 0.0, -3.0}, {3.0, 0.0, -3.0}},
	{{-3.0, 0.0, -5.0}, {-0.25, 0.0, -5.0}, {0.25, 0.0, -5.0}, {3.0, 0.0, -5.0}},
};

static float Xangle = 30.0, Yangle = 0.0, Zangle = 0.0; // Angles to rotate canoe.
static int rowCount = 0, columnCount = 0; // Indexes of selected control point.
// End globals.

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

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

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

// Drawing routine.
void drawScene(void)
{
   int i, j;
   glClear (GL_COLOR_BUFFER_BIT);
   glLoadIdentity();

   gluLookAt(0.0, 0.0, 12.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

   // Rotate scene.
   glRotatef(Zangle, 0.0, 0.0, 1.0);
   glRotatef(Yangle, 0.0, 1.0, 0.0);
   glRotatef(Xangle, 1.0, 0.0, 0.0);

   glPointSize(5.0);

   // Draw green control points.
   glColor3f(0.0, 1.0, 0.0);
   glBegin(GL_POINTS);
      for (i = 0; i < 6; i++)
         for (j = 0; j < 4; j++)
            glVertex3fv(controlPoints[i][j]);
   glEnd();
   
   // Draw the control polyhedron in light gray.
   glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
   glColor3f(0.7, 0.7, 0.7);
   for (i = 0; i < 5; i++)
   {
      glBegin(GL_QUAD_STRIP);
      for (j = 0; j < 4; j++)
	  {
         glVertex3fv(controlPoints[i][j]);
		 glVertex3fv(controlPoints[i+1][j]);
	  }
      glEnd();
   }

   // Draw red selected control point.
   glColor3f(1.0, 0.0, 0.0);
   glBegin(GL_POINTS);
      glVertex3fv(controlPoints[rowCount][columnCount]);
   glEnd();

   // Specify and enable the Bezier surface.
   glMap2f(GL_MAP2_VERTEX_3, 0, 1, 3, 4, 0, 1, 12, 6, controlPoints[0][0]); 
   glEnable(GL_MAP2_VERTEX_3); 

   // Draw the Bezier surface using a mesh approximation.
   glColor3f(0.0, 0.0, 0.0);
   glMapGrid2f(20, 0.0, 1.0, 20, 0.0, 1.0);
   glEvalMesh2(GL_LINE, 0, 20, 0, 20);

   // Draw the co-ordinate axes.
   glLineWidth(2.0);
   glColor3f(0.0, 0.0, 1.0);
   glBegin(GL_LINES);
	   glVertex3f(-6.0, 0.0, 0.0);
       glVertex3f(6.0, 0.0, 0.0);
       glVertex3f(5.75, 0.0, 0.25);
       glVertex3f(6.0, 0.0, 0.0);
       glVertex3f(5.75, 0.0, -0.25);
       glVertex3f(6.0, 0.0, 0.0);

	   glVertex3f(0.0, -6.0, 0.0);
       glVertex3f(0.0, 6.0, 0.0);
       glVertex3f(0.25, 5.75, 0.0);
       glVertex3f(0.0, 6.0, 0.0);
       glVertex3f(-0.25, 5.75, 0.0);
       glVertex3f(0.0, 6.0, 0.0);

	   glVertex3f(0.0, 0.0, -6.0);
       glVertex3f(0.0, 0.0, 6.0);
	   glVertex3f(0.25, 0.0, 5.75);
	   glVertex3f(0.0, 0.0, 6.0);
	   glVertex3f(-0.25, 0.0, 5.75);
	   glVertex3f(0.0, 0.0, 6.0);
   glEnd();
   glLineWidth(1.0);

   // Label the co-ordinate axes.
   glPushMatrix();
   glTranslatef(6.1, 0.0, 0.0);
   glScalef(0.005, 0.005, 0.005);
   writeStrokeString(GLUT_STROKE_ROMAN, "X");
   glPopMatrix();

   glPushMatrix();
   glTranslatef(0.0, 6.1, 0.0);
   glScalef(0.005, 0.005, 0.005);
   writeStrokeString(GLUT_STROKE_ROMAN, "Y");
   glPopMatrix();

   glPushMatrix();
   glTranslatef(0.0, 0.0, 6.1);
   glScalef(0.005, 0.005, 0.005);
   writeStrokeString(GLUT_STROKE_ROMAN, "Z");
   glPopMatrix();

   glutSwapBuffers();
}

// OpenGL window reshape routine.
void resize(int w, int h)
{
   glViewport(0, 0, (GLsizei)w, (GLsizei)h); 
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   gluPerspective(60.0, (float)w/(float)h, 1.0, 50.0);
   glMatrixMode(GL_MODELVIEW);
}

// Keyboard input processing routine.
void keyInput(unsigned char key, int x, int y)
{
   switch(key) 
   {
      case 27:
         exit(0);
         break;
      case 'x':
         Xangle += 5.0;
		 if (Xangle > 360.0) Xangle -= 360.0;
         glutPostRedisplay();
         break;
      case 'X':
         Xangle -= 5.0;
		 if (Xangle < 0.0) Xangle += 360.0;
         glutPostRedisplay();
         break;
      case 'y':
         Yangle += 5.0;
		 if (Yangle > 360.0) Yangle -= 360.0;
         glutPostRedisplay();
         break;
      case 'Y':
         Yangle -= 5.0;
		 if (Yangle < 0.0) Yangle += 360.0;
         glutPostRedisplay();
         break;
      case 'z':
         Zangle += 5.0;
		 if (Zangle > 360.0) Zangle -= 360.0;
         glutPostRedisplay();
         break;
      case 'Z':
         Zangle -= 5.0;
		 if (Zangle < 0.0) Zangle += 360.0;
         glutPostRedisplay();
         break;
      case 9:
		 {
		    if (rowCount < 5) rowCount++;
		    else rowCount = 0;
		 }
		 glutPostRedisplay();
		 break;
      case ' ':
		 {
		    if (columnCount < 3) columnCount++;
		    else columnCount = 0;
		 }
         glutPostRedisplay();
         break;
      default:
         break;
   }
}

// Callback routine for non-ASCII key entry.
void specialKeyInput(int key, int x, int y)
{
   if (key == GLUT_KEY_LEFT) controlPoints[rowCount][columnCount][0] -= 0.1;
   if (key == GLUT_KEY_RIGHT) controlPoints[rowCount][columnCount][0] += 0.1;
   if (key == GLUT_KEY_DOWN) controlPoints[rowCount][columnCount][1] -= 0.1;
   if (key == GLUT_KEY_UP) controlPoints[rowCount][columnCount][1] += 0.1;
   if (key == GLUT_KEY_PAGE_DOWN) controlPoints[rowCount][columnCount][2] -= 0.1;
   if (key == GLUT_KEY_PAGE_UP) controlPoints[rowCount][columnCount][2] += 0.1;
   glutPostRedisplay();
}

// Routine to output interaction instructions to the C++ window.
void printInteraction(void)
{
   cout << "Interaction:" << endl;
   cout << "Press space and tab to select a control point." << endl
        << "Press the right/left arrow keys to move the control point up/down the x-axis." << endl
        << "Press the up/down arrow keys to move the control point up/down the y-axis." << endl
        << "Press the page up/down keys to move the control point up/down the z-axis." << endl
        << "Press the x, X, y, Y, z, Z keys to rotate the viewpoint." << 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("bezierSurface.cpp");
   setup(); 
   glutDisplayFunc(drawScene); 
   glutReshapeFunc(resize);  
   glutKeyboardFunc(keyInput);
   glutSpecialFunc(specialKeyInput);
   glutMainLoop(); 

   return 0;  
}