perspective(3G)						       perspective(3G)

NAME    [Toc]    [Back]

     perspective - defines a perspective projection transformation

C SPECIFICATION    [Toc]    [Back]

     void perspective(fovy, aspect, near, far)
     Angle fovy;
     float aspect;
     Coord near, far;

PARAMETERS    [Toc]    [Back]

     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    [Toc]    [Back]

     perspective specifies a viewing pyramid into the world coordinate system.
     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.

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

SEE ALSO    [Toc]    [Back]

     mmode, ortho, viewport, window


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