glulookat(3g) [redhat man page]

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=_____

       UP'=______

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

					    s[0]  s[1]	s[2]  0
       M is then constructed as follows: M=(u[0]  u[1]	u[2]  0)
					    -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(3G), gluPerspective(3G)

																     GLULOOKAT(3G)

GLUPERSPECTIVE(3G)														GLUPERSPECTIVE(3G)

NAME

       gluPerspective - set up a perspective projection matrix

C SPECIFICATION

       void gluPerspective( GLdouble fovy,
			    GLdouble aspect,
			    GLdouble zNear,
			    GLdouble zFar )

PARAMETERS

       fovy    Specifies the field of view angle, in degrees, in the y direction.

       aspect  Specifies  the  aspect ratio that determines the field of view in the x direction.  The aspect ratio is the ratio of x (width) to y
	       (height).

       zNear   Specifies the distance from the viewer to the near clipping plane (always positive).

       zFar    Specifies the distance from the viewer to the far clipping plane (always positive).

DESCRIPTION

       gluPerspective specifies a viewing frustum into the world coordinate system.  In general, the aspect ratio in gluPerspective  should  match
       the  aspect ratio of the associated viewport. For example, aspect=2.0 means the viewer's angle of view is twice as wide in x as it is in y.
       If the viewport is twice as wide as it is tall, it displays the image without distortion.

       The matrix generated by gluPerspective is multipled by the current matrix, just as if glMultMatrix were called with the	generated  matrix.
       To load the perspective matrix onto the current matrix stack instead, precede the call to gluPerspective with a call to glLoadIdentity.

       Given f defined as follows:

								    f=cotangent(____)
       The generated matrix is

							   (______ 0	  0	      0      )
							       0   f	  0	      0
							       0   0 __________ _____________
							       0   0	-1	      0

NOTES

       Depth  buffer precision is affected by the values specified for zNear and zFar.	The greater the ratio of zFar to zNear is, the less effec-
       tive the depth buffer will be at distinguishing between surfaces that are near each other.  If

									 r=_____

       roughly log2r bits of depth buffer precision are lost.  Because r approaches infinity as zNear approaches 0, zNear must never be set to 0.

SEE ALSO

       glFrustum(3G), glLoadIdentity(3G), glMultMatrix(3G), gluOrtho2D(3G)

																GLUPERSPECTIVE(3G)