Flock plugin WIP

src/plugins/default-plugins.js

@@ -5,6 +5,7 @@ define([
     'plugins/sprite/animate',
     'plugins/sprite/8way',
     'plugins/sprite/track',
+    'plugins/sprite/flock',
 
     'plugins/layer/ui-layer',
     'plugins/layer/demo-trace', /* TODO: Delete and remove */

src/plugins/sprite/flock.js

@@ -0,0 +1,90 @@
+/*global define*/
+define(function() {
+
+    'use strict';
+
+    var sn;
+
+    /*
+     * The track plugin will call a callback function only whenever a
+     * sprite's position changes.
+     *
+     * Example options:
+     *
+     * var tracker = new _this.sn.ProximityTracker(100);
+     *
+     * updates:[{
+     *     name:'flock',
+     *     tracker: tracker,
+     *     flock_speed: 120,
+     *     flock_neighborhood: 50,
+     *     flock_neighbor_limit: 5
+     * }]
+     *
+     * flock_speed is in pixels/second. Initial sprite orientation should be set on the
+     * sprite with setDirection.
+     *
+     * flock_neighborhood is in pixels and defines the radius that defines the influential
+     * flockmates. Larger is generally better but slower, dependant on the tracker.
+     *
+     * flock_neighbor_limit is the number of neighbors that will contribute to the influence.
+     * E.g. if set to 5, only the 5 closest flockmates will influence the sprite. Larger is
+     * better, but slower. Set to a very large number to include all flockmates in the
+     * neighborhood.
+     *
+     * Sprites that flock with the same tracker will belong to the same flock.
+     *
+     * This plugin supports phasers and will flock more efficiently, but with less
+     * accuracy with phased updates.
+     *
+     */
+
+    function Flock() {
+    }
+
+    /** Called with the update options as the 'this' context, one of which
+     * is this.sprite, which refers to the sprite being updated.
+     * @param  {Number} now The time of the current frame
+     * @param  {Bool} phaseOn If the update is controlled by a phaser,
+     * this will be true to hint that we do a full batch of work, or false
+     * to hint that we try to exit as trivially as possible. Ignored on this
+     * plugin.
+     * @return true normally, or false to prevent any further
+     * plugins being called on this sprite for this frame.
+     */
+    Flock.prototype.update = function(now, phaseOn) {
+
+        var s = this.sprite;
+
+        this.tracker.find(s.x, s.y, this.flock_neighborhood, true);
+
+        return true;
+    };
+
+    Flock.prototype.onSpriteRemoved = function() {
+    };
+
+    Flock.prototype.init = function(s) {
+        this.sprite = s;
+
+        /* Some sensible defaults */
+
+        if (this.flock_speed===undefined) {
+            this.flock_speed = 120;
+        }
+
+        if (this.flock_neighborhood===undefined) {
+            this.flock_neighborhood = 50;
+        }
+
+        if (this.flock_neighbor_limit===5) {
+            this.flock_neighbor_limit = 5;
+        }
+    };
+
+    return function(snaps) {
+        sn = snaps;
+        sn.registerSpriteUpdater('flock', Flock);
+    };
+
+});