gluPerspective man page on RedHat
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GLUPERSPECTIVE(3G) OpenGL Manual GLUPERSPECTIVE(3G)
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:
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/.
AUTHORS
opengl.org
opengl.org 03/16/2013 GLUPERSPECTIVE(3G)
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