DragonFly On-Line Manual Pages

GLUPERSPECTIVE()                                              GLUPERSPECTIVE()

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 ((fovy/2))

       The generated matrix is

       ((((f/aspect) 0 0 0) (0 f 0 0) (0 0 ((zFar + zNear)/(zNear -
       zFar))(-1)) (0 0 ((2 * zFar * zNear)/(zNear - zFar)) 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
       effective the depth buffer will be at distinguishing between surfaces
       that are near each other.  If

       r = zFar/zNear

       roughly log_2 r 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, glLoadIdentity, glMultMatrix, gluOrtho2D

                                                              GLUPERSPECTIVE()