Draggable [] anchor = new Draggable[2];
Draggable [] control = new Draggable[2];
float t = 0.0;
void setup(){
  size(400,400,P3D);
  anchor[0] = new Draggable (100,100,100,10,color(100,100,200),color(100,200,200),"rect");
  anchor[1] = new Draggable (300,300,0,10,color(100,100,200),color(100,200,200),"rect");
  control[0] = new Draggable (100,300,-100,10,color(100,100,200),color(100,200,200),"ellipse");
  control[1] = new Draggable (300,100,0,10,color(100,100,200),color(100,200,200),"ellipse");
  ellipseMode(CENTER);
  rectMode(CENTER);
}
void draw(){
  background(144,130,140);
  directionalLight(100,100,100,0,0,-1);
  stroke(0);
  t = (t+0.01)%1.0;
  noStroke();
  fill(255);
  pushMatrix();
  translate(
  bezierPoint(anchor[0].x,control[0].x,control[1].x,anchor[1].x,t),
  bezierPoint(anchor[0].y,control[0].y,control[1].y,anchor[1].y,t),
  bezierPoint(anchor[0].z,control[0].z,control[1].z,anchor[1].z,t));
  sphere(10);
  popMatrix();
  pointLight(255,255,255,
  bezierPoint(anchor[0].x,control[0].x,control[1].x,anchor[1].x,t),
  bezierPoint(anchor[0].y,control[0].y,control[1].y,anchor[1].y,t),
  bezierPoint(anchor[0].z,control[0].z,control[1].z,anchor[1].z,t));
  stroke(0);
  bezier(
  anchor[0].x,anchor[0].y,anchor[0].z,control[0].x,control[0].y,control[0].z,
  control[1].x,control[1].y,control[1].z,anchor[1].x,anchor[1].y,anchor[1].z);
  for (int i = 0; i < 2; i++){
    anchor[i].draw();
    control[i].draw();
    anchor[i].update();
    control[i].update();
  }
}
class Draggable {
  int x,y,z,size,c1,c2;
  String mode;
  boolean locked = false;
  Draggable (int x, int y, int z, int size, color c1, color c2, String mode) {
    this.x = x;
    this.y = y;
    this.size = size;
    this.c1 = c1;
    this.c2 = c2;
    this.mode = mode;
  }
  void draw(){
    noStroke();
    if (locked || over()){
      fill(c1);
    }
    else{
      fill(c2);
    }
    if (mode == "rect"){
      pushMatrix();
      translate(x,y,z);
      box(size*2,size*2,size*2);
      popMatrix();
      noFill();
      stroke(c1);
      rect(x,y,size*2,size*2);
    }
    if (mode == "ellipse"){
      pushMatrix();
      translate(x,y,z);
      sphere(size);    
      popMatrix();
      noFill();
      stroke(c1);
      ellipse(x,y,size*2,size*2);
    }
  }
  void update(){
    if (over() && mousePressed){
      locked = true;
    }
    if (locked){
      x = mouseX;
      y = mouseY;
    }
    if (!mousePressed){
      locked = false;
    }
    if (over() && keyPressed){
      switch(key){
      case '-':
      case '_':
        z -= 2;
        break;
      case '=':
      case '+':
        z += 2;
        break;
      }
    }
  }
  boolean over(){
    if (mouseX <= x+size && mouseX >= x-size && mouseY <= y+size && mouseY >= y-size){
      return true;
    }
    else{
      return false;
    }
  }
}
float BezierPoint (float anchor0, float control0, float control1, float anchor1, float t) {
  float a = anchor1 - 3 * control1 + 3 * control0 - anchor0;
  float b = 3 * control1 - 6 * control0 + 3 * anchor0;
  float c = 3 * control0 - 3 * anchor0;
  float d = anchor0;
  return pow(t,3) * a + pow(t,2) * b + t * c + d;
}