glOrtho man page on Oracle
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GLORTHO(3G) OpenGL Manual GLORTHO(3G)
NAME
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 - leftt y = - top + bottom top -
bottomt 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/.
AUTHORS
opengl.org
opengl.org 04/29/2014 GLORTHO(3G)
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