Topology Module

Detailed Description

group a3d_topology_module

Creates and accesses topological entities.

This module defines the following types of topological entities:

  • Body: An exact 3D geometric representation of a solid, surfacic, or wireframe model. A topology body entity is contained in a representation item entity.

  • Connex: For solids, a connex represents a continuous piece of material.

  • Shell: A hollow sphere is represented by two shells (one inner and one outer).

  • Face: Every shell is represented by a collection of faces sewn together. Each face holds an associated geometric surface.

  • Loop: A face may be trimmed by several loops (one outer loop and multiple inner loops). Currently, HOOPS Exchange does not allow a face to have multiple outer loops. Instead, you can make several faces, each containing a single outer loop.

  • Co-edge: A loop is a collection of oriented and ordered co-edges, containing space parametric curves (if any), and neighboring information. The current version of HOOPS Exchange handles only manifold solids which are solids that have single neighbors per co-edge.

  • Edge: Each co-edge holds an edge, which in turn holds 3D information (if any), such as 3D curves and vertices.


In general, if the local tolerance is lower than the tolerance specified in the associated A3DTopoContext entity, you must use the tolerance from the A3DTopoContext entity.


An A3DTopoContext defines a global tolerance for every topological entity in this context. This global tolerance can then be superseded by less strict local tolerances for particular entities such as edges.