AP 242 Edition 2 has enhanced functionalities for 3D CAD Interoperability

The objective of this page is to provide an overview of the enhanced functionalities of AP242 Edition 2 in development for 3D CAD interoperability. It is summed up according to the following paragraphs:

- Overview and illustration of capabilities

- Examples of associated use cases

- Dependencies / related standards

- Status of development.

Overview and illustration of capabilities concerning the enhancement of 3D Geometry information model

Edition 2 capabilities and target use cases includes Edition 1 capabilities and supported use cases. Below are the capabilities and related targeted use cases brought by the 2nd Edition.

3D scan data

The support of 3D scan data was initially proposed for Part 42 ed4 but was postponed to a future edition in order not to impact the AP242 ed1 planning. New entities are needed to support very large sets of points (> 10 million points in a single set), and attributes on points or triangles (color, normal, etc).
Target use case: Exchange and Archiving of data coming from 3D scanners.

Curved triangles

Static tessellation can generate big files. A way to reduce the size of data to exchange / archive is to store in the STEP file the minimum necessary information to recreate the tessellation in the receiving system. The proposal is to introduce Curved Triangles, meaning non-planar triangles. Only a small number of curved triangles are needed to represent a sphere, when thousands of planar triangles are necessary to represent the same sphere with good accuracy. For example, it may be used to decrease the size of STEP files with 3D composite tessellated plies representation.
Various CAD systems and formats (like AMF) support this kind of tessellation. For systems supporting Dynamic Tessellation these Curved triangles will be easily converted into their own structures. Systems not supporting Dynamic Tessellation will convert the curved triangles into a static tessellation with the accuracy they want.

Surface visual texture

Tessellated data is often provided with textures: display of logos, complex drawings and better display of material. Textures are also used to reduce the size of context data: geometry is simplified to have fewer triangles, visual details are provided by textures (e.g. emboss).
Target use case: exchange and long term archiving of 3D context information.

Illustrations of texture need (left to right): 3D component without texture, same component with texture applied and other example of texture application.

Enhancements of specific construction history and parametric entities

AP 203 provides functionalities for interoperability of construction history and parametric design, included in AP 242 Ed1. PDES Inc pilots have demonstrated the feasibility of such functionalities on a limited use cases. Specific extensions or enhancement / simplification have been identified, to be included in AP 242 ed2.


Example of associated use cases 

Below are examples of uses cases covered by the Edition 2 Geometry extension :

-  File size reduction for high accuraccy additive manufacturing geometry data exchange between 2 CAD systems or between CAD and CAE systems or CAD systems and some manufacturing machines ;

-  Cloud of points (Millions of points) data exchange between scanners and CAD systems ;

-  Exchange of  surface texture data between CAD systems.

Note: the list is not exhaustive. For more information, refer to the CAX IF use cases and the STEP AP 242 use cases described by the respective industry associations.

Dependancies / related standards

STEP AP 242 CAD 3D geometry data model is based on AP242 Edition 1, and is also shared with STEP AP 209, AP 210, AP 238 standards (list not exhaustive).

Status of development

This 3D Geometry extension will be part of AP242 Edition 2 “Committee Draft” in beginning of year 2016. This 3D Geometry extension is under prototyping activities.