int count =4;                  // number of control vertices
int cap=128;                    // size of control arrays
pt[] P = new pt [cap]; 
pt[] SP = new pt [cap]; 
vec[] LP = new vec [cap]; 
int bi=-1;                       // index of selected vertex, -1 if none selected
pt Mouse = new pt(0,0);   // current mouse position
pt Last = new pt(0,0);   // clast point
color grey = color(200, 200, 210); 
color red = color(200, 10, 10); 
color blue = color(10, 10, 200); 
color lightblue = color(100, 100, 255); 
color green = color(10, 200, 20); 
color black = color(10, 10, 10); 
color magenta = color(250, 150, 200); 
boolean dots = true;
float d = 100.0, dd=200.0;
pt eye = new pt(-d,0);
boolean firstTime = true; 
float tt;
boolean straight = false;

void setup() 
{ 
  size(900, 400);  // framerate(30); 
  P[0]=new pt(-d,0.0);
  for (int i=1; i<count; i++) {P[i]=new pt(-sin((i+0.5)*TWO_PI/(count-1))*(width/6)+width*0.3,cos((i+0.5)*TWO_PI/(count-1))*(width/6));};
  P[1].x=d;            P[1].y=-height*.45;
  P[2].x=width/2-d;    P[2].y=P[1].y;
  P[3].x=P[2].x;       P[3].y=height*.45;
  strokeJoin(ROUND); strokeCap(ROUND);
  PFont font = loadFont("Courier-14.vlw"); textFont(font, 12);
} 
 
void draw() { 
  background(255); 
  translate(width/2,height/2);
  scale(1.0,-1.0);
  if (bi!= -1) {P[bi].setToMouse();};                    // snap selected vertex to mouse position during dragging
  P[0].y=0.0; d=-P[0].x;
  noStroke(); drawZone(d);
  stroke(grey); line(-width/2,0,width/2,0);   line(0,-height/2,0,height/2);
  fill(220); stroke(black); strokeWeight(2);  copyToSP(); drawSP();  noFill();
  stroke(green); strokeWeight(1); for (int i=1; i<20; i++) {transform(d*i); drawSP(); transform(-d*i);};
   stroke(black); strokeWeight(1); drawRays();
  stroke(magenta); strokeWeight(2); drawCentralRays();
  stroke(blue); strokeWeight(2); transform(d); drawSP(); 
  stroke(lightblue); strokeWeight(2); drawHorizontals(); 
  stroke(red); strokeWeight(2); drawDisplacements();
  P[0].show(5);
  
  };
  
void drawZone(float d) {  fill(255, 210, 20); 
  beginShape();  vertex(0,-height/2); vertex(0,height/2); vertex(d,height/2); vertex(d,-height/2); endShape();  };    

void transform(float d) {for (int i=1; i<count; i++) {SP[i].pers(d); }; }; 
void drawShape() {  beginShape();  for (int i=1; i<count; i++) {P[i].vert(); P[i].show(2);}; P[1].vert(); endShape();  };    
void drawSP() { beginShape();  for (int i=1; i<count; i++) {SP[i].vert();}; SP[1].vert(); endShape(); };    
void copyToSP() {for (int i=0; i<count; i++) {SP[i]=P[i].make();}; };    
  
void drawRays() {  for (int i=1; i<count; i++) {line(P[0].x,P[0].y,P[i].x,P[i].y); }; }; 
void drawCentralRays() {  for (int i=1; i<count; i++) {line(SP[i].x,SP[i].y,0,0); };   }; 
void drawHorizontals() {  for (int i=1; i<count; i++) {line(SP[i].x,SP[i].y,0,SP[i].y); };   }; 
       
void drawDisplacements() {  for (int i=1; i<count; i++) {SP[i].showLineTo(P[i]); };   }; 
       

//**************************************
// **** GUI FOR EDITING THE CONTROL CURVE
//**************************************
void mousePressed() {                                                   // to do when mouse is pressed  
  float bd=900;                                                     // init square of smallest distance to selected point
  Mouse.setToMouse();                                                   // save current mouse location
   for (int i=0; i<count; i++) { if (d2(i)<bd) {bd=d2(i); bi=i;  };};       // select closeest vertex
  if (bd>10) {                                                         // if closest vertex is too far
      bd=600;                                                       // reinitilize distance squared
      for (int i=0; i<count; i++) {if (dm(i)<bd) {bd=dm(i); bi=i;};};   // closest mid-edge point
      if (bd<20) {  
          for (int i=count-1; i>bi; i--) {P[i+1].setTo(P[i]);};                // shift down the rest 
          bi++;  P[bi].setTo(Mouse); count++;                                  // insert new vertex at mouse position
          }
        else {bi=-1;};                                                 // nothing selected
      };
  }

float d2(int j) {return (Mouse.disTo(P[j]));};   //  squared distance from mouse to vertex P[i]
float dm(int j) {return (Mouse.vecToMid(P[j],P[in(j)]).norm());};

void mouseReleased() {                                      // do this when mouse released

       bi= -1;   
  };
 

//**********************************
//***      CONTROL WITH KEYS
//**********************************
void keyPressed() {  
  if (key=='c') {straight=!straight;};
  if (key=='w') {writePts();};
  if (key=='s') {savePts();};
  if (key=='l') {loadPts();};
  if (key=='a') {                          // axis aligns the edges
      for (int i=0; i<count; i++) {
         if ( abs(P[in(i)].x-P[i].x)>abs(P[in(i)].y-P[i].y)) {float dy=(P[in(i)].y-P[i].y)/2; P[in(i)].y-=dy; P[i].y+=dy;}
          else {float dx=(P[in(i)].x-P[i].x)/2; P[in(i)].x-=dx; P[i].x+=dx;}
         };
     };
    };                                                                 

//**************************************
//**** utilities for polyloops
//**************************************
int in(int j) {  if (j==count-1) {return (0);}  else {return(j+1);}  };  // next vertex in control loop
int ip(int j) {  if (j==0) {return (count-1);}  else {return(j-1);}  };  // next vertex in control loop

void writePts() { for (int i=0; i<count; i++) {P[i].write();};};

void savePts() {
  String [] inppts = new String [count+1];
  int s=0;
  inppts[s++]=str(count);
  for (int i=0; i<count; i++) {inppts[s++]=str(P[i].x)+","+str(P[i].y);};
  saveStrings("loop.txt",inppts);
  };

void loadPts() {
  String [] ss = loadStrings("loop.txt");
  String subpts;
  int s=0;
  int comma;
  count = int(ss[s]);
  for(int i=0;i<count; i++) {
      comma=ss[++s].indexOf(',');
      P[i]=new pt (float(ss[s].substring(0, comma)), float(ss[s].substring(comma+1, ss[s].length())));
    };
  };