gluLookAt(3G)

NAME
     gluLookAt - define a viewing transformation


C SPECIFICATION
     void 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 reference
     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.
     Similarly, 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


     F = ( centerX   -   eyeX  )

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

     Then normalize as follows: f = _____

     UP' = ______
     Finally, let s = f x UP', and u = s x f.



     M is then constructed as follows:  M = (-s[0]  -s[1]  -s[2]  0  )
     and gluLookAt is equivalent to

          glMultMatrixf(M);
          glTranslated (-eyex, -eyey, -eyez);


SEE ALSO
     glFrustum, gluPerspective