gluLookAt(3G)		       OpenGL Reference			 gluLookAt(3G)

NAME    [Toc]    [Back]

     gluLookAt - define	a viewing transformation

C SPECIFICATION    [Toc]    [Back]

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

PARAMETERS    [Toc]    [Back]

     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    [Toc]    [Back]

     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||
     UP' = ______
	   ||UP||





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gluLookAt(3G)		       OpenGL Reference			 gluLookAt(3G)



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

					    ( s[0]   s[1]   s[2]  0  )
					    | u[0]   u[1]   u[2]  0  |
     M is then constructed as follows:	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    [Toc]    [Back]

     glFrustum,	gluPerspective


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