perspe(3G)

NAME
     perspe - defines a perspective projection transformation

FORTRAN SPECIFICATION
     subroutine perspe(fovy, aspect, near, far)
     integer*4 fovy
     real aspect, near, far

PARAMETERS
     fovy     expects the field-of-view angle in the y direction.  The field
              of view is the range of the area that is being viewed.  fovy
              must be > 2 or an error results.

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

     near     expects the distance from the viewer to the closest clipping
              plane (always positive).

     far      expects the distance from the viewer to the farthest clipping
              plane (always positive).

DESCRIPTION
     perspe specifies a viewing pyramid into the world coordinate system.  In
     general, the aspect ratio in perspe 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.

     When the system is in single matrix mode, perspe loads a matrix onto the
     transformation stack, replacing the current top matrix.  When the system
     is in viewing, projection, or texture matrix mode, perspe replaces the
     current Projection matrix and leaves the ModelView matrix stack and the
     Texture matrix unchanged.

SEE ALSO
     mmode, ortho, viewpo, window