- specify a plane against which all geometry is clipped



C SPECIFICATION


PARAMETERS

       _param1  Specifies  which  clipping  plane  is being posi-
                tioned.    Symbolic    names    of    the    form
                GL_CLIP_PLANEi,  where  i is an integer between 0
                and GL_MAX_CLIP_PLANES-1, are accepted.

       _param2  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  per-
       pendicular to the x, y, or z axis, against which all geom-
       etry is clipped.  To determine the maximum number of addi-
       tional  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,  _param2  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 _param1 is not an accepted
       value.