fieldkit/lib/physics/behaviours.js

Basic building blocks for computational design projects. Written in CoffeeScript for browser and server environments.

// Generated by CoffeeScript 1.6.3
(function() {
  var Attractor, Behaviour, Force, Vec2, Vec3, physics, vector,
    __hasProp = {}.hasOwnProperty,
    __extends = function(child, parent) { for (var key in parent) { if (__hasProp.call(parent, key)) child[key] = parent[key]; } function ctor() { this.constructor = child; } ctor.prototype = parent.prototype; child.prototype = new ctor(); child.__super__ = parent.prototype; return child; };

  vector = require('../math/vector');

  Vec2 = vector.Vec2;

  Vec3 = vector.Vec3;

  physics = require('./physics');

  Behaviour = physics.Behaviour;

  /*
  
    A constant force along a vector e.g. Gravity.
    Works in 2D + 3D.
  */


  Force = (function(_super) {
    var force;

    __extends(Force, _super);

    force = null;

    function Force(direction, weight) {
      this.direction = direction;
      this.weight = weight != null ? weight : 1;
    }

    Force.prototype.prepare = function() {
      return force = this.direction.normalizeTo(this.weight);
    };

    Force.prototype.apply = function(particle) {
      return particle.position.add(force);
    };

    Force.prototype.toString = function() {
      return "Force(" + force + ")";
    };

    return Force;

  })(Behaviour);

  /*
  
    Attracts each particle within range to a target point.
    Works in 2D + 3D.
  */


  Attractor = (function() {
    var rangeSq, tmp;

    tmp = null;

    rangeSq = 0;

    function Attractor(target, range, weight) {
      this.target = target;
      this.range = range;
      this.weight = weight != null ? weight : 1;
      tmp = this.target.clone();
    }

    Attractor.prototype.prepare = function() {
      return rangeSq = this.range * this.range;
    };

    Attractor.prototype.apply = function(particle) {
      var dist, distSq;
      tmp.set(this.target).sub(particle.position);
      distSq = tmp.lengthSquared();
      if (distSq > 0 && distSq < rangeSq) {
        dist = Math.sqrt(distSq);
        tmp.scale((1 / dist) * (1 - dist / this.range) * this.weight);
        return particle.force.add(tmp);
      }
    };

    Attractor.prototype.toString = function() {
      return "Attractor(" + this.target + ", " + this.range + ", " + this.weight + ")";
    };

    return Attractor;

  })();

  module.exports = {
    Force: Force,
    Attractor: Attractor
  };

}).call(this);