    You may change the orientation of an object or texture pattern by adding
 a 'rotate' parameter.  It consists of the keyword 'rotate' followed by a
 vector.  The three terms of the vector specify the number of degrees to ro-
 tate about each of the x, y, and z axes.

    NOTE: The order of the rotations does matter.  Rotations occur about the
 x axis first, then the y axis, then the z axis.  If you are not sure if this
 is what you want then you should use multiple rotation statements to get a
 correct rotation.  You should only rotate on one axis at a time.  As in:
       rotate <0, 30, 0>                // 30 degrees around Y axis
       rotate <-20, 0, 0>               // -20 degrees around X axis
       rotate <0, 0, 10>                // 10 degrees around Z axis

    Rotation is always performed relative to the axis.  Thus if an object is
 some distance from the axis of rotation, its will not only rotate but it
 will 'orbit' about the axis as though it was swinging around on an invisible
 string.

    To work out the rotation directions, you must perform the famous 'Compu-
 ter Graphics Aerobics' exercise.  Hold up your left hand.  Point your thumb
 in the positive direction of the axis of rotation.  Your fingers will curl
 in the positive direction of rotation.  Similarly if you point your thumb in
 the negative direction of the axis your fingers will curl in the negative
 direction of rotation.  This is the famous 'left-hand coordinate system'.

                    +Y
                    |    +Z _
                    |    /_| |_  _
                    |   _| | | |/ \
                    |  | | | | |  |
                    | /| | | | |  V
                    |/ | | | | |
       -X ----------+--|-|-|-|-|------ +X
                   /|  |        \____
                  / |  |          ___|
                 /  |  \         /
                /   |   |       /
                   -Z    |
                        -Y

    In this illustration, the left hand is curling around the X axis.  The
 thumb points in the positive X direction and the fingers curl over in the
  positive rotation direction.

    If you want to use a right hand system, as some CAD systems such as Auto-
 CAD do, the 'right' vector in the camera specification needs to be changed.
 See the detailed description of the camera.  In a right handed system you
 use your right hand for the 'Aerobics'.
