GraphicComponent Hierarchy
This conceptual topic would give an introduction to graphic component hierarchy.
Hierarchy
Part
A Part is a container for bodies, and can hold zero or more bodies. A Part also contains an orientation.
Body
A Body is typically a single 3D solid or a 2D surface, but it can also be several disjoint lumps treated as one body. It is the highest level object in the geometric model. Several bodies can be grouped in a Part.
Shell
A Shell is a set of connected Faces and Wires. It is normally the outside of a solid body, but can also be the inside of a hollow body.
Face
A Face is a bounded portion of a single geometric surface, the two-dimensional analog of a body. The boundary is represented by one or more loops or edges. Each face is simply connected, implying that one can traverse from any point on the interior of the face to any other point on the interior of the face without crossing the boundary of the face. In general, it is not meaningful to distinguish exterior and interior loops of edges, though for certain surface types this may be possible and some algorithms may do so.
Wire
A Wire is a collection of Edges that are connected to each other, without being attached to a Face.
Loop
A Loop is a set of connected coedges. Normally it has no start or end points.
Coedge
A Coedge is closely related to an edge. A coedge stores its relationships with adjacent edges and with superior owning entities. (In some contexts, the coedge may be viewed as the use of an edge by a face or wire.) The data structures formed by these relationships (stored as pointers) and their interpretation depend upon the nature of the owning entity.
Edge
An Edge is bounded by one or more vertices, referring to one Vertex at each end. Edges are closely related to Coedges, which allows the Edge to occur in more than one Face, thus makes it possible to create solids.
Vertex
A Vertex refers to a point in object space, and is the corner of either a Face or a Wire.