fgluPerspective(3G) OpenGL Reference fgluPerspective(3G)NAMEfgluPerspective - set up a perspective projection matrix
FORTRAN SPECIFICATION
SUBROUTINE fgluPerspective( REAL*4 fovy,
REAL*4 aspect,
REAL*4 zNear,
REAL*4 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).
DESCRIPTIONfgluPerspective specifies a viewing frustum into the world coordinate
system. In general, the aspect ratio in fgluPerspective 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 fgluPerspective 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 fgluPerspective with a call to glLoadIdentity.
Given f defined as follows:
f = cotangent(____)
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fgluPerspective(3G) OpenGL Reference fgluPerspective(3G)
The generated matrix is
( ______ 0 ____0_____ _____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 = _____
roughly log2r 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, glLoadIdentity, glMultMatrix, fgluOrtho2D
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