1991-2006
Silicon Graphics, Inc.
glOrtho
3G
glOrtho
multiply the current matrix with an orthographic matrix
C Specification
void glOrtho
GLdouble left
GLdouble right
GLdouble bottom
GLdouble top
GLdouble nearVal
GLdouble farVal
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.
nearVal
farVal
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
right
-
left
0
0
t
x
0
2
top
-
bottom
0
t
y
0
0
-2
farVal
-
nearVal
t
z
0
0
0
1
where
t
x
=
-
right
+
left
right
-
left
t
y
=
-
top
+
bottom
top
-
bottom
t
z
=
-
farVal
+
nearVal
farVal
-
nearVal
Typically, the matrix mode is GL_PROJECTION, and
left
bottom
-
nearVal
and
right
top
-
nearVal
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).
-
farVal
specifies the location of the far clipping plane.
Both nearVal and farVal 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.
GL_INVALID_OPERATION is generated if glOrtho
is executed between the execution of
glBegin
and the corresponding execution of glEnd.
Associated Gets
glGet with argument GL_MATRIX_MODE
glGet with argument GL_COLOR_MATRIX
glGet with argument GL_MODELVIEW_MATRIX
glGet with argument GL_PROJECTION_MATRIX
glGet with argument GL_TEXTURE_MATRIX
See Also
glFrustum,
glMatrixMode,
glMultMatrix,
glPushMatrix,
glViewport
Copyright
Copyright 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/.