gluPerspective()                                 gluPerspective()

NAME    [Toc]    [Back]

       gluPerspective - set up a perspective projection matrix

SYNOPSIS    [Toc]    [Back]

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

PARAMETERS    [Toc]    [Back]

       Specifies  the  field  of view angle, in degrees, in the y
       direction.  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).  Specifies the  distance
       from  the  viewer to the near clipping plane (always positive).
  Specifies the distance from the viewer to the  far
       clipping plane (always positive).

DESCRIPTION    [Toc]    [Back]

       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
       2*zFar*zNear  /  zNear  -   zFar   0                     0
       -1                             0

NOTES    [Toc]    [Back]

       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    [Toc]    [Back]

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



                                                 gluPerspective()