text: /*
   * Aurora: https://github.com/pixelmatix/aurora
   * Copyright (c) 2014 Jason Coon
   *
   * Portions of this code are adapted from "Attractor" in "The Nature of Code" by Daniel Shiffman: http://natureofcode.com/
   * Copyright (c) 2014 Daniel Shiffman
   * http://www.shiffman.net
   *
   * Permission is hereby granted, free of charge, to any person obtaining a copy of
   * this software and associated documentation files (the "Software"), to deal in
   * the Software without restriction, including without limitation the rights to
   * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
   * the Software, and to permit persons to whom the Software is furnished to do so,
   * subject to the following conditions:
   *
   * The above copyright notice and this permission notice shall be included in all
   * copies or substantial portions of the Software.
   *
   * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
   * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
   * FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
   * COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
   * IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
   * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
   */
  
  #include "Vector.h"
  
  class Attractor {
  public:
      float mass;    // Mass, tied to size
      float G;       // Gravitational Constant
      PVector location;   // Location
  
      Attractor() {
          location = PVector(MATRIX_CENTRE_X, MATRIX_CENTRE_Y);
          mass = 10;
          G = .5;
      }
  
      PVector attract(Boid m) {
          PVector force = location - m.location;   // Calculate direction of force
          float d = force.mag();                              // Distance between objects
          d = constrain(d, 5.0, 32.0);                        // Limiting the distance to eliminate "extreme" results for very close or very far objects
          force.normalize();                                  // Normalize vector (distance doesn't matter here, we just want this vector for direction)
          float strength = (G * mass * m.mass) / (d * d);     // Calculate gravitational force magnitude
          force *= strength;                                  // Get force vector --> magnitude * direction
          return force;
      }
  };
  