GLULOOKAT(3G)															     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

	    centerX - eyeX
	F = centerY - eyeY
	    centerZ - eyeZ

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

       Then normalize as follows: f = F/ || F ||

       UP' = UP/|| UP ||

       Finally, let s = f X UP', and u = s X f.

       M is then constructed as follows:

	     s[0]    s[1]    s[2]    0
	     u[0]    u[1]    u[2]    0
	M = -f[0]   -f[1]   -f[2]    0
	      0       0       0      1

       and gluLookAt is equivalent to

       glMultMatrixf(M);

       glTranslated (-eyeX, -eyeY, -eyeZ);

SEE ALSO

       glFrustum, gluPerspective

																     GLULOOKAT(3G)