NAME
	  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_PLANEi, 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_PLANEi, 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_PLANEi = 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_PLANEi

     SEE ALSO
	  glEnable