# glClipControl.3G - Man Page

control clip coordinate to window coordinate behavior

## C Specification

**void glClipControl(GLenum** *origin***, GLenum** *depth***);**

## Parameters

*origin*Specifies the clip control origin. Must be one of

**GL_LOWER_LEFT**or**GL_UPPER_LEFT**.*depth*Specifies the clip control depth mode. Must be one of

**GL_NEGATIVE_ONE_TO_ONE**or**GL_ZERO_TO_ONE**.

## Description

**glClipControl** controls the clipping volume behavior and the clip coordinate to window coordinate transformation behavior.

The view volume is defined by $$z_{min} \leq z_c \leq w_c$$ where $z_{min} = -w_c$ when *depth* is **GL_NEGATIVE_ONE_TO_ONE**, and $z_{min} = 0$ when *depth* is **GL_ZERO_TO_ONE**.

The normalized device coordinate $y_d$ is given by $$y_d = { { f \times y_c } \over w_c }$$ where $f = 1$ when *origin* is **GL_LOWER_LEFT**, and $f = -1$ when *origin* is **GL_UPPER_LEFT**.

The window coordinate $z_w$ is given by $$z_w = s \times z_d + b$$ where $s = { { f - n } \over 2 }$ and $b = { {n + f} \over 2 }$ when *depth* is **GL_NEGATIVE_ONE_TO_ONE**, and $s = f - n$ and $b = n$ when *depth* is **GL_ZERO_TO_ONE**. $n$ and $f$ are the near and far depth range values set with **glDepthRange**().

Finally, the polygon area computation defined by **gl_FrontFacing**() to determine if a polygon is front- or back-facing has its sign negated when *origin* is **GL_UPPER_LEFT**.

## Notes

The default GL clip volume definition is for a *origin* of **GL_LOWER_LEFT** and a *depth* of **GL_NEGATIVE_ONE_TO_ONE**.

An *origin* of **GL_UPPER_LEFT** and a *depth* of **GL_ZERO_TO_ONE** corresponds to Direct3D's clip volume definition.

An *origin* of **GL_UPPER_LEFT** and a *depth* of **GL_NEGATIVE_ONE_TO_ONE** corresponds to the upper-left origin of the window coordinate system of Microsoft Windows and the X Window System.

There is extensive discussion of the uses and further consequences of the different clip volume settings in the GL_ARB_clip_control extension specification in the OpenGL Registry at URL http://www.opengl.org/registry/.

## Errors

An **GL_INVALID_ENUM** error is generated if *origin* is not **GL_LOWER_LEFT** or **GL_UPPER_LEFT**.

An **GL_INVALID_ENUM** error is generated if *depth* is not **GL_NEGATIVE_ONE_TO_ONE** or **GL_ZERO_TO_ONE**.

## Version Support

OpenGL Version | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|

Function / Feature Name | 2.0 | 2.1 | 3.0 | 3.1 | 3.2 | 3.3 | 4.0 | 4.1 | 4.2 | 4.3 | 4.4 | 4.5 |

glClipControl | - | - | - | - | - | - | - | - | - | - | - | ✔ |

## See Also

gl_ClipDistance(), gl_CullDistance(), gl_FrontFacing(), glDepthRange().

## Copyright

Copyright © 2014 Khronos Group. This material may be distributed subject to the terms and conditions set forth in the Open Publication License, v 1.0, 8 June 1999. http://opencontent.org/openpub/.

## Copyright

Copyright © 2014 Khronos Group