#include <stdio.h>
#include <stdlib.h>
#include <GLUT/glut.h>

/*
 * bezier.c: cubic bezier curve
 *
 * Of necessity, this is 2D.
 *
 * All calcs are 3d, though.
 *
 * 3/31/03 pjf
 *
 */

#define NPMAX 10000

GLfloat p[NPMAX][3];

int np=0; // # of valid control points

int curcp = -1;

int ww,hh;


float b0(float u) { return (1.0-u)*(1.0-u)*(1.0-u)/6.0; }
float b1(float u) { return (4.0-6.0*u*u+3.0*u*u*u)/6.0;}
float b2(float u) { return (1.0+3.0*u+3.0*u*u-3.0*u*u*u)/6.0; }
float b3(float u) { return u*u*u/6.0; }

/* display callback */
void display() {
 float u;
 int i;
 glClear(GL_COLOR_BUFFER_BIT);
 if (np>3) {
  glColor3f(1.0,1.0,1.0);
  glBegin(GL_LINE_STRIP);
  for(i=0;i<(np-3);i++) {
   for (u=0.0;u<=1.0;u+=0.01) {
    GLfloat x = b0(u)*p[i+0][0] + b1(u)*p[i+1][0]  + b2(u)*p[i+2][0] + b3(u)*p[i+3][0];
    GLfloat y = b0(u)*p[i+0][1] + b1(u)*p[i+1][1]  + b2(u)*p[i+2][1] + b3(u)*p[i+3][1];
    GLfloat z = b0(u)*p[i+0][2] + b1(u)*p[i+1][2]  + b2(u)*p[i+2][2] + b3(u)*p[i+3][2];
    glVertex3f(x,y,z);
    }
   }
  glEnd();
  glColor3f(0.8,0.2,0.3);
  glPointSize(5);
  glBegin(GL_POINTS);
  for(i=0;i<(np-3);i++) {
   for (u=0.0;u<=1.0;u+=1.0) {
    GLfloat x = b0(u)*p[i+0][0] + b1(u)*p[i+1][0]  + b2(u)*p[i+2][0] + b3(u)*p[i+3][0];
    GLfloat y = b0(u)*p[i+0][1] + b1(u)*p[i+1][1]  + b2(u)*p[i+2][1] + b3(u)*p[i+3][1];
    GLfloat z = b0(u)*p[i+0][2] + b1(u)*p[i+1][2]  + b2(u)*p[i+2][2] + b3(u)*p[i+3][2];
    glVertex3f(x,y,z);
    }
   }
  glEnd();
  }
 // now draw boxes around control points
 for (i=0;i<np;i++) {
  float colors[4][3] = { { 1.0,0.0,0.0},{0.0,1.0,0.0},{0.0,0.0,1.0},{0.5,0.5,0.5}};
  GLfloat x = p[i][0] - 0.02;
  GLfloat y = p[i][1] - 0.02;
  GLfloat z = p[i][2];
  glColor3f(colors[i%4][0],colors[i%4][1],colors[i%4][2]);
  glBegin(GL_LINE_LOOP);
   glVertex3f(x,y,z);
   glVertex3f(x+0.04,y,z);
   glVertex3f(x+0.04,y+0.04,z);
   glVertex3f(x,y+0.04,z);
  glEnd();
  }
 glFlush();
 }


/* mouse: called when a mouse button is pressed or released.
   btn identifies which button; state identifies "press" or "release" */
void mouse(int btn, int state, int x, int y) {
 //fprintf(stderr,"mouse: btn %d, state %d, location (%d,%d).\n",btn,state,x,y);
 if (btn == GLUT_LEFT_BUTTON) {
  if (state==GLUT_UP) { curcp = -1; }
  else {
   int i;
   float xmouse=2.0*x/ww - 1.0; 
   float ymouse=2.0*(hh-y)/hh - 1.0;
   float zmouse=0.0;
   //fprintf(stderr,"Mousedown @ %f %f\n",xmouse,ymouse);
   for(i=0;i<np;i++) {
    float d=(xmouse-p[i][0])*(xmouse-p[i][0]) + 
            (ymouse-p[i][1])*(ymouse-p[i][1]) +
            (zmouse-p[i][2])*(zmouse-p[i][2]);
    if (d<0.007) break;
    };
   if (i<np) { curcp = i; };
   }
  }
  else if (btn == GLUT_MIDDLE_BUTTON) {
   if ((state == GLUT_DOWN) && (np<NPMAX-1)){
    p[np][0] = 2.0*x/ww-1.0;
    p[np][1] = 2.0*(hh-y)/ww-1.0;
    p[np][2] = 0.0;
    curcp = np;
    np++;
    glutPostRedisplay();
    }
   }
 }

/* called initially (before first call to display()) and whenever the
   window is resized */
void reshape(int w, int h) {
  fprintf(stderr,"reshape: new size %d x %d.\n",w,h);
  // must update viewport and clipping planes
  glViewport(0, 0, w, h);
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  glOrtho(-1.0,1.0,-1.0,1.0,-1.0,1.0);
  glMatrixMode(GL_MODELVIEW);
  ww=w; hh=h;
}

void motion(int x, int y) {
 float xmouse=2.0*x/ww - 1.0; 
 float ymouse=2.0*(hh-y)/hh - 1.0;
 float zmouse = 0.0;
 //fprintf(stderr,"Motion: loc (%d %d).\n",x,y);
 //fprintf(stderr,"Motion @ %f %f\n",xmouse,ymouse);
 if (curcp == -1) return;
 p[curcp][0] = xmouse;
 p[curcp][1] = ymouse;
 p[curcp][2] = zmouse;
 glutPostRedisplay();
 }
 
void init(void) {
 /* nothing to do! */
 }

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB);
    glutInitWindowSize(500, 500);
    glutCreateWindow(argv[0]);
    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutMouseFunc(mouse);
    glutMotionFunc(motion);
    init();
    glutMainLoop();
    return 0;
}