20. Flag using curves.txt

#include <Windows.h>
#include <GL\glew.h>
#include <GL\freeglut.h>
#include <iostream>
#include <math.h>

#define NUMSTEPS 0.01
#define tension 0.00
GLfloat P[4][4][3] = {
   {{-4.5, -4.5, 12.0}, {-1.5, -4.5, 6.0}, 
    {1.5, -4.5, -3.0}, {4.5, -4.5, 6.0}}, 
   {{-4.5, -1.5, 3.0}, {-1.5, -1.5, 9.0}, 
    {1.5, -1.5, 0.0}, {4.5, -1.5, -3.0}}, 
   {{-4.5, 1.5, 12.0}, {-1.5, 1.5, 0.0}, 
    {1.5, 1.5, 9.0}, {4.5, 1.5, 12.0}}, 
   {{-4.5, 4.5, -6.0}, {-1.5, 4.5, -6.0}, 
    {1.5, 4.5, 0.0}, {4.5, 4.5, -3.0}}
};
 
 
GLfloat D[] = {1.0f, 1.0f, 0.0f, 0.0f,
               0.0f, 0.0f, 1.0f, 1.0f,
               0.0f, 0.33333333333333f, 0.0f, 0.0f,
			   0.0f, 0.0f, -0.33333333333333f, 0.0f};
GLfloat DT[] = {1.0f, 0.0f, 0.0f, 0.0f,
                1.0f, 0.0f, 0.33333333333333f, 0.0f,
                0.0f, 1.0f, 0.0f, -0.33333333333333f,
			    0.0f, 1.0f, 0.0f, 0.0f};
 
GLfloat StartPt_u(int ii,int jj){
 
	return P[jj][1][ii]; 
}
 
GLfloat EndPt_u(int ii,int jj){
    return P[jj][2][ii]; 
}
 
GLfloat StartTan_u(int ii,int jj){
	return(   (1-tension)*(P[jj][2][ii] - P[jj][0][ii])  /2 ); 
}
 
GLfloat EndTan_u(int ii,int jj){
	return(   (1-tension)*(P[jj][3][ii] - P[jj][1][ii])/2  ); 
}
 
GLfloat StartPt_w(int ii,int jj){
	return P[1][jj][ii]; 
}
 
GLfloat EndPt_w(int ii,int jj){
    return P[2][jj][ii]; 
}
 
GLfloat StartTan_w(int ii,int jj){
	return(   (1-tension)*(P[2][jj][ii] - P[0][jj][ii])  /2 ); 
}
 
GLfloat EndTan_w(int ii,int jj){
	return(   (1-tension)*(P[3][jj][ii] - P[1][jj][ii])/2  ); 
}
 
 
 
 
void Spline_u(int piece_s,int piece_e){
	int i,j;
	double t, vv[3];
	double inc;
	inc = NUMSTEPS;
 
       for(j=piece_s-1;j<piece_e;j++){
    glBegin(GL_LINE_STRIP);
	for(t=0; t<=1; t+=inc){
		for(i=0;i<3;i++){
			vv[i] = ((2*t*t*t)-(3*t*t)+1)*StartPt_u(i,j)
				+ ((-2*t*t*t)+(3*t*t))*EndPt_u(i,j)
				+ ((t*t*t)-(2*t*t)+t)*StartTan_u(i,j)
				+ ((t*t*t)-(t*t))*EndTan_u(i,j);
		}
		glColor3d(0.0,0.0,0.0);
	  glVertex3dv(vv);
	}
     glEnd();
    }
}
 
void Spline_w(int piece_s,int piece_e){
	int i,j;
	double t, vv[3];
	double inc;
	inc = NUMSTEPS;
	       for(j=piece_s-1;j<piece_e;j++){
    glBegin(GL_LINE_STRIP);
	for(t=0; t<1; t+=inc){
		for(i=0;i<3;i++){
			vv[i] = ((2*t*t*t)-(3*t*t)+1)*StartPt_w(i,j)
				+ ((-2*t*t*t)+(3*t*t))*EndPt_w(i,j)
				+ ((t*t*t)-(2*t*t)+t)*StartTan_w(i,j)
				+ ((t*t*t)-(t*t))*EndTan_w(i,j);
		}
 
		glColor3d(0.0,0.0,0.0);
	  glVertex3dv(vv);
	}
     glEnd();
    }
}
 
void draw_splinegrid()
{  
  // Spline_u(2, 3);
  // Spline_w(2, 3); 
 
}
GLfloat B[4][4][3];
void convert(int ii)
{
 
int i,j;
GLfloat p00 = StartPt_u(ii,1);
GLfloat p10 = EndPt_w(ii,1);
GLfloat p00u = StartTan_w(ii,1);
GLfloat p10u = StartTan_w(ii,2);
GLfloat p01 = EndPt_u(ii, 1);
GLfloat p11 = EndPt_w(ii,2);
GLfloat p01u = EndTan_w(ii,1);
GLfloat p11u = EndTan_w(ii,2);
 
GLfloat p00w = StartTan_u(ii,1);
GLfloat p10w = StartTan_u(ii,2);
 
GLfloat p01w = EndTan_u(ii,1);
GLfloat p11w = EndTan_u(ii,2);          
GLfloat C[] = {p00, p10, p00u, p10u,
               p01, p11, p01u, p11u,
               p00w, p10w, 0.0f, 0.0f,
			   p01w, p11w, 0.0f, 0.0f};
GLfloat m[16];
 
 glMatrixMode(GL_MODELVIEW);
glLoadMatrixf (D);
 
 
glMultMatrixf (C);
 
 
glMultMatrixf(DT);
 
glGetFloatv(GL_MODELVIEW_MATRIX,m);
  for(i=0;i<4;i++){
	  for(j=0;j<4;j++){
		  B[i][j][ii]=m[4*i+j];
 
	  }
 
	  }
 } 
 
void Bvertex()
{
	int i;
	for(i = 0; i < 3; i++){
		convert(i);
	}
glLoadIdentity();
}

void display(void)
{
	int i, j;
  glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
   glColor3f(1.0, 1.0, 1.0);
   //glMatrixMode(GL_MODELVIEW);
   glPushMatrix ();
   glRotatef(15.0, 1.0, 1.0, 1.0);
   glEvalMesh2(GL_FILL, 0, 100, 0, 100);

   glColor3f(0.0, 0.0, 0.0);
   glLineWidth(2.0);
   
 
      for (j = 0; j <= 3; j++) {
      /*glBegin(GL_LINE_STRIP);
      for (i = 0; i <= 100; i++)
         glEvalCoord2f((GLfloat)i/100.0, (GLfloat)j/8.0);
      glEnd();*/

      glBegin(GL_LINE_STRIP);
      for (i = 0; i <= 100; i++)
         glEvalCoord2f((GLfloat)j/3.0, (GLfloat)i/100.0);
      glEnd();

   }

 
   //draw_splinegrid();   
   glPopMatrix ();
   glFlush();
 
}
 
void init(void)
{
	Bvertex();
   glClearColor (0.0, 0.0, 0.0, 0.0);
   glMap2f(GL_MAP2_VERTEX_3, 0, 1, 3, 4, 0, 1, 12, 4, &B[0][0][0]);
 glEnable(GL_MAP2_VERTEX_3);
  glMapGrid2f(100, 0.0, 1.0, 100, 0.0, 1.0);
   glEnable(GL_DEPTH_TEST);
   glShadeModel(GL_FLAT);
    glEnable(GL_LINE_SMOOTH);
	 glEnable(GL_POINT_SMOOTH);
 
}
 
void reshape(GLsizei w, GLsizei h)
{  if(h==0)
   h=1;
   glViewport(0, 0, w, h);
   glMatrixMode(GL_PROJECTION);
   glLoadIdentity();
   if (w <= h)
      glOrtho(-4.0, 4.0, -4.0*(GLfloat)h/(GLfloat)w, 
        4.0*(GLfloat)h/(GLfloat)w, -20.0, 20.0);
   else
      glOrtho(-4.0*(GLfloat)w/(GLfloat)h, 
              4.0*(GLfloat)w/(GLfloat)h, -4.0, 4.0, -20.0, 20.0);
   glMatrixMode(GL_MODELVIEW);
   glLoadIdentity();
}
 
int main(int argc, char** argv)
{
 
   glutInit(&argc, argv);
   glutInitDisplayMode (GLUT_SINGLE | GLUT_RGB | GLUT_DEPTH);
   glutInitWindowSize (400, 400); 
   glutInitWindowPosition (100, 100);
   glutCreateWindow (argv[0]);
   init();
   glutDisplayFunc(display);
   glutReshapeFunc(reshape);
   //glutKeyboardFunc(keyboard);
   glutMainLoop();
   return 0;
 
}