20032004
Silicon Graphics, Inc.
glOrtho
3G
glOrtho
glOrthof
glOrthox
multiply the current matrix with an orthographic
matrix
C Specification
void glOrthof
GLfloat left
GLfloat right
GLfloat bottom
GLfloat top
GLfloat near
GLfloat far
void glOrthox
GLfixed left
GLfixed right
GLfixed bottom
GLfixed top
GLfixed near
GLfixed far
Parameters
left,
right
Specify the coordinates for the left and right
vertical clipping planes.
bottom,
top
Specify the coordinates for the bottom and top
horizontal clipping planes.
near,
far
Specify the distances to the nearer and farther
depth clipping planes. These values are negative if the
plane is to be behind the viewer.
Description
glOrtho
describes a transformation that produces a parallel projection.
The current matrix (see
glMatrixMode)
is multiplied by this matrix and the result replaces the
current matrix, as if
glMultMatrix
were called with the following matrix as its argument:
(
2
rightleft
0
0
tx
0
2
topbottom
0
ty
0
0
2
farnear
tz
0
0
0
1
)
where
tx
=

right+left
rightleft
ty
=

top+bottom
topbottom
tz
=

far+near
farnear
Typically, the matrix mode is
GL_PROJECTION, and
(left, bottom,
near) and
(right, top,
near)
specify the points on the near clipping plane that are mapped
to the lower left and upper right corners of the window,
respectively, assuming that the eye is located at (0, 0, 0).
far
specifies the location of the far clipping plane. Both
near and far
can be either positive or negative.
Use
glPushMatrix
and
glPopMatrix
to save and restore the current matrix stack.
Errors
GL_INVALID_VALUE is generated if
left = right, or
bottom = top, or
near = far.
See Also
glFrustum,
glMatrixMode,
glMultMatrix,
glPushMatrix,
glViewport
Copyright
Copyright 20032004
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.