GLUPERSPECTIVE
Section: Misc. Reference Manual Pages (3G)
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NAME
gluPerspective
 set up a perspective projection matrix
C SPECIFICATION
void gluPerspective(
GLdouble fovy,
GLdouble aspect,
GLdouble zNear,
GLdouble zFar )
delim $$
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" over 2}")"
The generated matrix is
left ( ~~ down 130 { matrix {
ccol { {f over "aspect"} above 0 above 0 above 0 }
ccol { 0 above f above 0 above 0 }
ccol { 0 above 0 above {{"zFar" + "zNear"} over {"zNear"  "zFar"}} above 1 }
ccol { 0 above 0 above {{2 * "zFar" * "zNear"} over {"zNear"  "zFar"}} above 0}
}} ~~~ right )
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
$r ~=~ "zFar" over "zNear"$
roughly $log sub 2 r$ bits of depth buffer precision are lost.
Because $r$ approaches infinity as zNear approaches 0,
zNear must never be set to 0.
SEE ALSO
glFrustum(3G), glLoadIdentity(3G),
glMultMatrix(3G), gluOrtho2D(3G)
Index
 NAME

 C SPECIFICATION

 PARAMETERS

 DESCRIPTION

 NOTES

 SEE ALSO

linux.jgfs.net manual pages