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

Pascal
procedure perspective(fovy: Angle; aspect: real; near, far: Coord);

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 which 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 given as a ratio of x to y.  In general, the aspect ratio given in the perspective command should match the aspect ratio of the associated viewport.  For example, aspect=2.0 means the viewer sees twice as far in x as in y.  If the viewport is twice as wide as it is tall, the image will be displayed without distortion.  The arguments near and far are distances from the viewer to the near and far clipping planes, and these are always positive.  perspective loads a matrix onto the transformation stack, overwriting whatever was there. 

fovy is in 10th of degrees, as are all angles.  fov must be ≥ 2 or an error will result. 
 

SEE ALSO

ortho, window

Version 2.4  —  May 08, 1986