1991-2006 Silicon Graphics, Inc.
gluPerspective 3G
gluPerspective set up a perspective projection matrix

## C Specification

void `gluPerspective` GLdouble fovy GLdouble aspect GLdouble zNear GLdouble zFar

## Parameters

fovy

  Specifies the field of view angle, in degrees, in the y direction.

aspect

  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).

zNear

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

zFar

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

## Description

`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 multiplied 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

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

gluOrtho2D, glFrustum, glLoadIdentity, glMultMatrix

## Copyright

Copyright 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.