Lesson 2.2 – Vector Fields

  int gridWidth = 40; 
  int gridHeight = 40; 
  int screenWidth = 700;
  int screenHeight = 700;
  int xOffset;
  int yOffset;
  int distX;
  int distY;
  PVector reactorPosition;
  ArrayList <VectorLine> vectLineList = new ArrayList<VectorLine>();
  
  void setup() {
    reactorPosition = new PVector(0, 0);
    size(700, 700);
    background(255);
    smooth();
  
    int xOffset = floor(width/2-(distX*gridWidth/2));
    int yOffset = floor(height/2-(gridHeight*distY/2));
    int distX = width/gridWidth+1;
    int distY = height/gridHeight+1;
  
    for (int i = 0; i<gridWidth; i++ ) {
      for (int j = 0; j<gridHeight; j++ ) {
        vectLineList.add(new VectorLine(i*distX, j*distY));
      }
    }
  };
  
  void draw() {
    background(255);
    for (int i = 0; i<vectLineList.size(); i++ ) {
      vectLineList.get(i).draw(reactorPosition);
    };
  };
  
  
  void mouseMoved() {
    reactorPosition.x = mouseX;
    reactorPosition.y = mouseY;
  };
  
  
  class VectorLine {
    PVector _pos;
    PVector _vector;
    float reactorScaler = .07;
  
    VectorLine(int x, int y) {
      _vector = new PVector(0, 5);
      _pos = new PVector(x, y);
      _vector.add(_pos);
    }
  
    void draw(PVector reactor) {
      float reactorDistance = dist(reactor.x, reactor.y, _pos.x, _pos.y);
      float scaler = reactorDistance*reactorScaler;
      PVector _reactor  = reactor.copy();
      stroke(0);
      _reactor.sub(_pos);
      _vector = _reactor.copy();
      _vector.normalize();
      _vector.rotate(PI/4); // 
      _vector.mult(scaler);
      _vector.add(_pos);
      line(_pos.x, _pos.y, _vector.x, _vector.y); 
      ellipse(_vector.x, _vector.y, 5, 5);
    }
  }