ObjectARX ® allows you to define a clipping boundary for geometry contained within xrefs and blocks. The clip-boundary portion of the AcGi API allows compound objects (blocks and objects that behave like blocks) to express these clip boundaries to the AcGi implementation.
During worldDraw() or viewportDraw() any drawable may specify a polygonal clip boundary with which to clip its graphics. The following sections describe how to use this API feature.