     @x = -@x
     @y = -@y
     @z = -@z
-
     return @
 
   add: (vec) ->
     @x += vec.x
     @y += vec.y
     @z += vec.z
-
     return @
 
   subtract: (vec) ->
     @x -= vec.x
     @y -= vec.y
     @z -= vec.z
-
     return @
 
   multiply: (s) ->
     @x *= s
     @y *= s
     @z *= s
-
     return @
 
   divide: (s) ->

    @x *= rs
    @y *= rs
    @z *= rs

    return @

  norm: ->

        @z = z

  set: (x, y, z) ->
    if arguments.length == 1
      vec = x
      @x = vec.x
      @y = vec.y
      @z = vec.z
    else
      @x = x
      @y = y
      @z = z

    return @

