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<STRONG>NAME</STRONG>
<STRONG>glClipPlane</STRONG> - specify a plane against which all geometry is
clipped
<STRONG>C</STRONG> <STRONG>SPECIFICATION</STRONG>
void <STRONG>glClipPlane</STRONG>( GLenum <EM>plane</EM>,
const GLdouble *<EM>equation</EM> )
<STRONG>PARAMETERS</STRONG>
<EM>plane</EM> Specifies which clipping plane is being
positioned. Symbolic names of the form
<STRONG>GL_CLIP_PLANE</STRONG><EM>i</EM>, where <EM>i</EM> is an integer between 0
and <STRONG>GL_MAX_CLIP_PLANES</STRONG> -1, are accepted.
<EM>equation</EM> Specifies the address of an array of four double-
precision floating-point values. These values are
interpreted as a plane equation.
<STRONG>DESCRIPTION</STRONG>
Geometry is always clipped against the boundaries of a six-
plane frustum in <EM>x</EM>, <EM>y</EM>, and <EM>z</EM>. <STRONG>glClipPlane</STRONG> allows the
specification of additional planes, not necessarily
perpendicular to the <EM>x</EM>, <EM>y</EM>, or <EM>z</EM> axis, against which all
geometry is clipped. To determine the maximum number of
additional clipping planes, call <STRONG>glGetIntegerv</STRONG> with argument
<STRONG>GL_MAX_CLIP_PLANES</STRONG>. 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.
<STRONG>glClipPlane</STRONG> specifies a half-space using a four-component
plane equation. When <STRONG>glClipPlane</STRONG> is called, <EM>equation</EM> 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 <EM>in</EM> with
respect to that clipping plane. Otherwise, it is <EM>out</EM>.
To enable and disable clipping planes, call <STRONG>glEnable</STRONG> and
<STRONG>glDisable</STRONG> with the argument <STRONG>GL_CLIP_PLANE</STRONG><EM>i</EM>, where <EM>i</EM> is the
plane number.
All clipping planes are initially defined as (0, 0, 0, 0) in
eye coordinates and are disabled.
<STRONG>NOTES</STRONG>
It is always the case that <STRONG>GL_CLIP_PLANE</STRONG>i = <STRONG>GL_CLIP_PLANE0</STRONG> +
i.
<STRONG>ERRORS</STRONG>
<STRONG>GL_INVALID_ENUM</STRONG> is generated if <EM>plane</EM> is not an accepted
value.
<STRONG>GL_INVALID_OPERATION</STRONG> is generated if <STRONG>glClipPlane</STRONG> is executed
between the execution of <STRONG>glBegin</STRONG> and the corresponding
execution of <STRONG>glEnd</STRONG>.
<STRONG>ASSOCIATED</STRONG> <STRONG>GETS</STRONG>
<STRONG>glGetClipPlane</STRONG>
<STRONG>glIsEnabled</STRONG> with argument <STRONG>GL_CLIP_PLANE</STRONG><EM>i</EM>
<STRONG>SEE</STRONG> <STRONG>ALSO</STRONG>
<STRONG>glEnable</STRONG>
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