C SPECIFICATION

       void GLAPIENTRY gluLookAt( GLdouble eyeX,
                                  GLdouble eyeY,
                                  GLdouble eyeZ,
                                  GLdouble centerX,
                                  GLdouble centerY,
                                  GLdouble centerZ,
                                  GLdouble upX,
                                  GLdouble upY,
                                  GLdouble upZ )

PARAMETERS

       eyeX, eyeY, eyeZ
                       Specifies the position of the eye point.

       centerX, centerY, centerZ
                       Specifies the position of the reference point.

       upX, upY, upZ   Specifies the direction of the up vector.

DESCRIPTION

       gluLookAt  creates a viewing matrix derived from an eye point, a refer-
       ence point indicating the center of the scene, and an UP vector.

       The matrix maps the reference point to the negative z axis and the  eye
       point  to  the  origin.   When a typical projection matrix is used, the
       center of the scene therefore maps to the center of the viewport.  Sim-
       ilarly,  the  direction  described  by the UP vector projected onto the
       viewing plane is mapped to the positive y axis so that it points upward
       in  the  viewport.   The  UP vector must not be parallel to the line of
       sight from the eye point to the reference point.

       Let
          centerX - eyeX

























          centerZ - eyeZ


       Let UP be the vector (upX,upY,upZ).

       Then normalize as follows: f=__F<I>F___

       UP?=__U<I>U_P<I>P___


       Finally, let s=fxUP?, and u=sxf.

                                            s[0]  s[1]  s[2]  0



















                                            u[0]  u[1]  u[2]  0









       M is then constructed as follows: M=(                   )















                                              0     0     0   1

       and gluLookAt is equivalent to glMultMatrixf(M);  glTranslated  (-eyex,
       -eyey, -eyez);

       glFrustum, gluPerspective



                                                                 GLULOOKAT(3G)