**glOrtho**

### NAME

**glOrtho** -- multiply the current matrix by an orthographic matrix
### C SPECIFICATION

void **glOrtho**(GLdouble *left*,
GLdouble *right*,
GLdouble *bottom*,
GLdouble *top*,
GLdouble *near*,
GLdouble *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 distances are negative if the plane is to be behind the viewer.

### DESCRIPTION

**glOrtho** describes a matrix that produces a parallel projection.
(*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. The corresponding matrix is

where

The current matrix is multiplied by this matrix with the result replacing
the current matrix. That is, if M is the current matrix and O is the
ortho matrix, then M is replaced with M*O.

Use
**glPushMatrix** and
**glPopMatrix**
to save and restore the current matrix stack.

### ERRORS

**GL_INVALID_OPERATION** is generated if **glOrtho** is called between
a call to **glBegin** and the corresponding
call to **glEnd**.
### ASSOCIATED GETS

**glGet** with argument
**GL_MATRIX_MODE**

**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**

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© *1995 Uwe Behrens. All rights reserved.*