Name
gluPerspective — set up a perspective projection matrix
C Specification
void gluPerspective | ( | GLdouble fovy, GLdouble aspect, GLdouble zNear, GLdouble zFar); |
Python Specification
gluPerspective | ( | fovy, aspect, zNear, zFar) → None |
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.