GLUPERSPECTIVE(3G) 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
------------ 0 0 0
aspect
0 f 0 0
zFar+zNear 2*zFar*zNear
0 0 ---------- ------------zNear-zFar -----------zNear-zFar
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
r = zFar/zNear
roughly log2(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)
GLUPERSPECTIVE(3G)
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