# Method GL.glOrtho()

- Method
**glOrtho** `void`

**glOrtho(**`float`

`left`

,`float`

`right`

,`float`

`bottom`

,`float`

`top`

,`float`

`zNear`

,`float`

`zFar`

**)**- 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: .sp .ce .EQ left ( matrix { ccol { {2 over {"right" - "left"}} above 0 above 0 above 0 } ccol { 0 above {2 over {"top" - "bottom"}} above 0 above 0 } ccol { 0 above 0 above {-2 over {"zFar" - "zNear"}} above 0 } ccol { {t sub x}~ above {t sub y}~ above {t sub z}~ above 1~ } } right ) .EN

where .ce .EQ t sub x ~=~ -{{"right" + "left"} over {"right" - "left"}} .EN

.ce .EQ t sub y ~=~ -{{"top" + "bottom"} over {"top" - "bottom"}} .EN

.ce .EQ t sub z ~=~ -{{"zFar" + "zNear"} over {"zFar" - "zNear"}} .EN

.RE

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.

- Parameter
`left`

Specify the coordinates for the left and right vertical clipping planes.

- Parameter
`bottom`

Specify the coordinates for the bottom and top horizontal clipping planes.

- Parameter
`zNear`

Specify the distances to the nearer and farther depth clipping planes. These values are negative if the plane is to be behind the viewer.

- Throws
GL_INVALID_OPERATION is generated if glOrtho is executed between the execution of glBegin and the corresponding execution of glEnd.