实体定义
继承关系
GfcRoot
└
GfcGeometry
└GfcTopology
├
GfcPolygon
├
GfcEdge
├
GfcPolyhedralFace
├
GfcPolyhedralLoop
├
GfcPolyhedralEdge
├
GfcCoedge
├
GfcCoedgeListEx
├
GfcSimpleLoop
├
GfcCoedgeList
└
GfcSimpleVertex