1991-2006
Silicon Graphics, Inc.
glClipPlane
3G

# glClipPlane

specify a plane against which all geometry is clipped

## C Specification

                    void glClipPlane
                    GLenum plane
                    const GLdouble * equation

## Parameters

`plane`

  Specifies which clipping plane is being positioned. Symbolic names of the form `GL_CLIP_PLANE` i, where i is an integer between 0 and `GL_MAX_CLIP_PLANES` -1 , are accepted.

`equation`

  Specifies the address of an array of four double-precision floating-point values. These values are interpreted as a plane equation.

## Description

Geometry is always clipped against the boundaries of a six-plane frustum in x, y, and z. `glClipPlane` allows the specification of additional planes, not necessarily perpendicular to the x, y, or z axis, against which all geometry is clipped. To determine the maximum number of additional clipping planes, call glGetIntegerv with argument `GL_MAX_CLIP_PLANES`. All implementations support at least six such clipping planes. Because the resulting clipping region is the intersection of the defined half-spaces, it is always convex.

`glClipPlane` specifies a half-space using a four-component plane equation. When `glClipPlane` is called, `equation` is transformed by the inverse of the modelview matrix and stored in the resulting eye coordinates. Subsequent changes to the modelview matrix have no effect on the stored plane-equation components. If the dot product of the eye coordinates of a vertex with the stored plane equation components is positive or zero, the vertex is in with respect to that clipping plane. Otherwise, it is out.

To enable and disable clipping planes, call glEnable and glDisable with the argument `GL_CLIP_PLANE` i, where i is the plane number.

All clipping planes are initially defined as (0, 0, 0, 0) in eye coordinates and are disabled.

## Notes

It is always the case that `GL_CLIP_PLANE` i = `GL_CLIP_PLANE0` + i.

## Errors

`GL_INVALID_ENUM` is generated if `plane` is not an accepted value.

`GL_INVALID_OPERATION` is generated if `glClipPlane` is executed between the execution of glBegin and the corresponding execution of glEnd.

## Associated Gets

glGetClipPlane

glIsEnabled with argument `GL_CLIP_PLANE` i

## See Also

glEnable

## 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/.