Attractor.h

/*
 * 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;
    }
};