**NAME**
**glOrtho** - multiply the current matrix with an orthographic
matrix
**C** **SPECIFICATION**
void **glOrtho**( GLdouble *left*,
GLdouble *right*,
GLdouble *bottom*,
GLdouble *top*,
GLdouble *zNear*,
GLdouble *zFar* )
**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.
*zNear*, *zFar* 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:
( )
|_____**_**____ 0 0 t |
|right-left x |
| _____**_**____ |
| 0 top-bottom 0 ty |
| |
| 0 0 ____**__**____ t |
| zFar-zNear z |
| 0 0 0 1 |
( )
where
t = -**__________**
x right-left
t = -**__________**
y top-bottom
t = -**__________**
z zFar-zNear
Typically, the matrix mode is **GL_PROJECTION**, and (*left*,
*bottom*, -*zNear*) and (*right*, *top*, -*zNear*) 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).
-*zFar* specifies the location of the far clipping plane.
Both *zNear* and *zFar* can be either positive or negative.
Use **glPushMatrix** and **glPopMatrix** to save and restore the
current matrix stack.
**ERRORS**
**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_MODELVIEW_MATRIX**
**glGet** with argument **GL_PROJECTION_MATRIX**
**glGet** with argument **GL_TEXTURE_MATRIX**
**SEE** **ALSO**
**glFrustum**, **glMatrixMode**, **glMultMatrix**, **glPushMatrix**,
**glViewport**