Interactive Draggable Bezier Path in Processing

interactiveBezier.pde

Bezier b;
ArrayList<DraggablePoint> pts;
boolean isDragging;
int dragID;

float slope;

float t;
void setup(){
  
  t = 0.0f;
  isDragging = false;
  dragID = -1;
  size(1280,720);
  b = new Bezier();
  b.a = new DraggablePoint(random(width),random(height));
  b.ca = new DraggablePoint(random(width),random(height));
  b.cb = new DraggablePoint(random(width),random(height));
  b.b = new DraggablePoint(random(width),random(height));
  
  pts = new ArrayList<DraggablePoint>();
  pts.add(b.a);
  pts.add(b.b);
  pts.add(b.ca);
  pts.add(b.cb);
  
}
void draw(){
  t += 0.0025f;
  if(t>1.0f){
   t = 0.0f ;
  }
  background(255);
  b.draw();
  
  Point p = b.plot(t);
  stroke(0,32,64);
  noFill();
  ellipse(p.x,p.y,10,10);
  
  Point slopePtA = new Point(p.x+cos(slope)*30, p.y+sin(slope)*30);
  Point slopePtB = new Point(p.x+cos(slope)*-30, p.y+sin(slope)*-30);
  
  line(p.x,p.y,slopePtA.x,slopePtA.y);
  line(p.x,p.y,slopePtB.x,slopePtB.y);
 // println(dragID);
}
void mouseDragged(){
   if(isDragging){
    DraggablePoint thisPt = pts.get(dragID);
    thisPt.x = mouseX;
    thisPt.y = mouseY;
  }
}
void mouseMoved(){
 
  int nearestID = -1;
  float nearestDist = 100; // nearer than 100 selects
  
  for(int i=0;i<pts.size();i++){
    DraggablePoint thisPt = pts.get(i);
    thisPt.isSelected = false;
     float thisDist = dist(thisPt.x,thisPt.y,mouseX,mouseY);
     if(thisDist<nearestDist){
      nearestDist = thisDist;
      nearestID = i;
     }
  }
  if(nearestID>-1){
   pts.get(nearestID).isSelected = true; 
  }
  
}

void mousePressed(){
for(int i=0;i<pts.size();i++){
      DraggablePoint thisPt = pts.get(i);
  if(thisPt.isSelected == true){
   thisPt.isDragging = true; 
   dragID = i;
   isDragging = true;
  }
}
}
void mouseReleased(){
 isDragging = false;
 pts.get(dragID).isDragging = false;
 dragID = -1;
}
class Point{
 float x,y;
 Point(float _x, float _y){
  x = _x;
  y = _y;
 }
}
class DraggablePoint extends Point{
  boolean isSelected;
  boolean isDragging;
  DraggablePoint(float _x, float _y){
    super(_x,_y); 
       isSelected = isDragging = false;
      
  }
  void draw(){
    if(isDragging){
      noStroke();
      fill(0,255,0);
    } else if(isSelected){
    noStroke();
    fill(255,0,0);
   } else {
    noStroke();
    fill(0);
   }
   ellipse(x,y,5,5); 
  }
}
class Bezier{
  DraggablePoint a,b,ca,cb;
  
  // plot a point along the curve
Point plot(float pct_in){
  float pct = max(0.0f,min(pct_in,1.0f));
  float cX = 3*(ca.x-a.x);
  float bX = 3*(cb.x-ca.x)-cX;
  float aX = b.x-a.x-cX-bX;
  float cY = 3*(ca.y-a.y);
  float bY = 3*(cb.y-ca.y)-cY;
  float aY = b.y-a.y-cY-bY; //  +ofRandom(-10,10);
  
  // get the slope
  // http://stackoverflow.com/a/15399173
  float t = pct;
 float B0_dt = -3*(1-t)*(1-t);
float B1_dt = 3*(1-t)*(1-t) -6*t*(1-t);
float B2_dt = - 3*t*t + 6*t*(1-t);
float B3_dt = 3*t*t;
float  px_dt = (B0_dt * a.x) + (B1_dt * ca.x) + (B2_dt * cb.x) + (B3_dt * b.x);
float py_dt = (B0_dt * a.y) + (B1_dt * ca.y) + (B2_dt * cb.y) + (B3_dt * b.y);
  slope = atan2(py_dt,px_dt);
//println(slope);

  Point returnVal = new Point(0,0);
  returnVal.x = aX*pct*pct*pct + bX*pct*pct + cX*pct + a.x; //+ofRandom(-5,5);
  returnVal.y = aY*pct*pct*pct + bY*pct*pct + cY*pct + a.y;
  text("a",aX,aY);
  text("b",bX,bY);
  text("c",cX,cY);
  
  return returnVal;
}
  
  void draw(){
    stroke(0);
    noFill();
   bezier(a.x,
   a.y,
   ca.x,
   ca.y,
   cb.x,
   cb.y,
   b.x,
   b.y);
   stroke(128);
   line(a.x,a.y,
   ca.x,ca.y);
   line(b.x,b.y,
   cb.x,cb.y);
   a.draw();
   b.draw();
   ca.draw();
   cb.draw();
  }
}