Industrial automation systems and integration —
Product data representation and exchange —
Part 42:
Integrated generic resource: Geometric and topological representation

1 Scope

The following are in the scope of the geometry schema:

• definition of points, vectors, parametric curves and parametric surfaces;
• definition of finite volumes with internal parametrisation;
• definition of transformation operators;
• points defined directly by their coordinate values or in terms of the parameters of an existing curve or surface;
• definition of conic curves and elementary surfaces;
• definition of curves defined on a parametric surface;
• definition of general parametric spline curves, surfaces and volumes;
• definition of locally refined spline curves, surfaces and volumes;
• definition of point, curve and surface replicas;
• definition of offset curves and surfaces;
• definition of intersection curves.

The following are in the scope of the topology schema:

• definition of the fundamental topological entities vertex, edge, and face, each with a specialised subtype to enable it to be associated with the geometry of a point, curve, or surface, respectively;
• collections of the basic entities to form topological structures of path, loop and shell and constraints to ensure the integrity of these structures;
• the association of faces with geometric volumes;
• orientation of topological entities.

The following are in the scope of the geometric model schema:

• data describing the precise geometric form of three-dimensional solid
• objects;
• constructive solid geometry (CSG) models;
• CSG models in two-dimensional space;
• definition of CSG primitives and half-spaces;
• creation of solid models by sweeping operations;
• manifold boundary representation (B-rep) models;
• constraints to ensure the integrity of B-rep models;
• surface models;
• wireframe models;
• geometric sets;
• creation of a replica of a solid model in a new location;
• tessellated geometry;
• the association of tessellated geometry with exact geometry.

The following are in the scope of the scan data 3d shape model schema:

• representation of a shape as a cloud of points produced by a scanning process.

The following are outside the scope of this document:

• all other forms of procedurally defined curves and surfaces;
• curves and surfaces which do not have a parametric form of representation;
• any form of explicit representation of a ruled surface.

  NOTE    For a ruled surface the geometry is critically dependent upon the parametrisation of the boundary curves and the method of associating pairs of points on the two curves. A ruled surface with B-spline boundary curves can however be exactly represented by the B-spline surface entity.

• spatial occupancy forms of solid models (such as octree models);
• geometric tolerances;
• implicit forms of representation in terms of features;
• assemblies and mechanisms.

© ISO 2021 — All rights reserved