function Path3D(path, firstNormal, raw) {
            if (firstNormal === void 0) { firstNormal = null; }
            this.path = path;
            this._curve = new Array();
            this._distances = new Array();
            this._tangents = new Array();
            this._normals = new Array();
            this._binormals = new Array();
            for (var p = 0; p < path.length; p++) {
                this._curve[p] = path[p].clone(); // hard copy
            }
            this._raw = raw || false;
            this._compute(firstNormal);
        }
new Path3D(path, normal, raw)
Creates a Path3D. A Path3D is a logical math object, so not a mesh.
please read the description in the tutorial :  http://doc.babylonjs.com/tutorials/How_to_use_Path3D
path : an array of Vector3, the curve axis of the Path3D
normal (optional) : Vector3, the first wanted normal to the curve. Ex (0, 1, 0) for a vertical normal.
raw (optional, default false) : boolean, if true the returned Path3D isn't normalized. Useful to depict path acceleration or speed.