fglClipPlane(3G)

NAME
     fglClipPlane - specify a plane against which all geometry is clipped


FORTRAN SPECIFICATION
     SUBROUTINE fglClipPlane( INTEGER*4 plane,
                              CHARACTER*8 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. fglClipPlane 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 fglGetIntegerv 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.

     fglClipPlane specifies a half-space using a four-component plane
     equation.  When fglClipPlane 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 fglEnable and fglDisable 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 fglClipPlane is executed between the
     execution of fglBegin and the corresponding execution of fglEnd.
ASSOCIATED GETS
     fglGetClipPlane
     fglIsEnabled with argument GL_CLIP_PLANEi


SEE ALSO
     fglEnable