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/.