babylon-navigation-mesh/lib/Channel.js

A toolkit to move on navigation mesh with BABYLONJS

var Class = require("abitbol");
var BABYLON = require("babylonjs");

var Channel = Class.$extend({
	__init__: function() {
	    this.portals = [];
	},

	push: function (p1, p2) {
		if (p2 === undefined) p2 = p1;
		this.portals.push({
			left: p1,
			right: p2
		});
	},

	_vequal: function (a, b) {
		return BABYLON.Vector3.DistanceSquared(a, b) < 0.00001;
	},

	_triarea2: function (a, b, c) {
		var ax = b.x - a.x;
		var az = b.z - a.z;
		var bx = c.x - a.x;
		var bz = c.z - a.z;
		return bx * az - ax * bz;
	},

	stringPull: function () {
		var portals = this.portals;
		var pts = [];
		// Init scan state
		var portalApex, portalLeft, portalRight;
		var apexIndex = 0,
			leftIndex = 0,
			rightIndex = 0;

		portalApex = portals[0].left;
		portalLeft = portals[0].left;
		portalRight = portals[0].right;

		// Add start point.
		pts.push(portalApex);

		for (var i = 1; i < portals.length; i++) {
			var left = portals[i].left;
			var right = portals[i].right;

			// Update right vertex.
			if (this._triarea2(portalApex, portalRight, right) >= 0.0) {
				if (this._vequal(portalApex, portalRight) || this._triarea2(portalApex, portalLeft, right) < 0.0) {
					// Tighten the funnel.
					portalRight = right;
					rightIndex = i;
				} else {
					// Right over left, insert left to path and restart scan from portal left point.
					pts.push(portalLeft);
					// Make current left the new apex.
					portalApex = portalLeft;
					apexIndex = leftIndex;
					// Reset portal
					portalLeft = portalApex;
					portalRight = portalApex;
					leftIndex = apexIndex;
					rightIndex = apexIndex;
					// Restart scan
					i = apexIndex;
					continue;
				}
			}

			// Update left vertex.
			if (this._triarea2(portalApex, portalLeft, left) <= 0.0) {
				if (this._vequal(portalApex, portalLeft) || this._triarea2(portalApex, portalRight, left) > 0.0) {
					// Tighten the funnel.
					portalLeft = left;
					leftIndex = i;
				} else {
					// Left over right, insert right to path and restart scan from portal right point.
					pts.push(portalRight);
					// Make current right the new apex.
					portalApex = portalRight;
					apexIndex = rightIndex;
					// Reset portal
					portalLeft = portalApex;
					portalRight = portalApex;
					leftIndex = apexIndex;
					rightIndex = apexIndex;
					// Restart scan
					i = apexIndex;
					continue;
				}
			}
		}

		if ((pts.length === 0) || (!this._vequal(pts[pts.length - 1], portals[portals.length - 1].left))) {
			// Append last point to path.
			pts.push(portals[portals.length - 1].left);
		}

		this.path = pts;
		return pts;
	}
});

module.exports = Channel;