perspecti(3g) — 4D1 2.0



     perspective(3G)                                   perspective(3G)



     NAME

          perspective - defines a perspective projection

          transformation


     SPECIFICATION

          C         perspective(fovy, aspect, near, far)

                    Angle fovy;

                    float aspect;

                    Coord near, far;




          FORTRAN   subroutine perspe(fovy, aspect, near, far)

                    integer*4 fovy

                    real aspect, near, far


     DESCRIPTION

          perspective defines a projection transformation by

          indicating the field-of-view angle (fovy) in the y direction

          of the eye coordinate system; the aspect ratio that

          determines the field of view in the x direction; and the

          distance to the near and far clipping planes in the z

          direction. The aspect ratio is a ratio of x to y. In

          general, the aspect ratio in perspective 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.  near and

          far are the distances from the viewer to the near and far

          clipping planes, and are always positive.


          perspective loads a matrix onto the transformation stack,

          overwriting what was there.


          fovy is in tenths of degrees, as are all angles.  fovy must

          be > 2 or an error results.


     SEE ALSO

          ortho, window


          Programming Guide, Section 4.3, Projection Transformations















     Page 1                                          (printed 8/20/87)
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