OpenGL man pages
## gluPerspective.3gl

## Name

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 multipled 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:
*fovy*
f = cotangent(----)
2
The generated matrix is
| f |
| ------ 0 0 0 |
| *aspect* |
| |
| 0 f 0 0 |
| |
| *zFar*+*zNear* 2**zFar***zNear* |
| 0 0 ---------- ------------ |
| *zNear*-*zFar* *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
*zFar*
r = -----
*zNear*
roughly log r bits of depth buffer precision are lost. Because r
2
approaches infinity as *zNear* approaches zero, *zNear* must never be set to
zero.

## See Also

glFrustum, glLoadIdentity, glMultMatrix, gluOrtho2D

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Last Edited: *
Fri Dec 6 11:18:03 EST 1996
*
by
*AFV*

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