ISO 10303-42

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

Scope

This document specifies the integrated generic resource constructs for geometric and topological representation.  The following are within the scope of this document:
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.