Data selection act

Major engineering software vendors are challenging native CAD data files with their own lightweight
‘open’ publishing formats for both 2D drawings and 3D models. Charles Clarke reviews some of them.

In today’s ‘write-once/read-maybe’ culture 80 per cent of business event data is never accessed after being stored; and it is never modified by one user, let alone by many.

So do we use relational database technology (RDB) simply because it’s there? Similarly, there is significant marketing hype about the need to share native CAD data, and many vendors have multiple translation facilities to enable data sharing — but why?

Unless your process acts specifically on the 3D data for analysis, rapid prototyping or machining, sharing is unnecessary. In fact, to preserve the intellectual property of your design it is actually desirable to limit the extent to which the detailed data is made available to third parties.

In a highly collaborative design environment many other users need to be able to examine your data for estimating or quoting purposes, buying in materials, organising logistics, producing packaging or a multitude of other related activities. But in these kinds of situations native CAD data is not only serious overkill, but a significant hindrance — the files aren’t small and therefore don’t e-mail easily.

As a result, all the major engineering software vendors are promoting their own lightweight ‘open’ publishing formats for 2D drawings and 3D models.

Autodesk has continued to promote and expand its DWF format, IBM/ Dassault has recently announced its 3D XML format, UGS has delivered a free JT-based utility and Intel has been promoting its U3D approach.

With the previous release of Acrobat, Adobe concentrated on increasing the 2D drawing capability of PDF, especially from within AutoCAD. With the latest release it now deals with 3D.

There is also a range of applications from proprietary vendors that have grown up around the needs of collaboration that can produce a much more compact data format than native CAD files. They contain all the relevant geometric information needed by other collaborating parties (who don’t need native CAD data) and they can include non-geometric data or files useful in these other activities.

Actify’s SpinFire Professional, for example, streamlines communication of CAD files and associated data by enabling users to save and share this design data as a compact .3D file. Engineers, individuals with quoting and estimating responsibilities and IT can use the software and its .3D WorkSpace feature to electronically organise and publish associated design files and documentation within a Windows environment.

They can include CAD data from diverse native CAD systems, then add notes and other related documents, hyperlinks, multiple models, plus mark-ups and necessary measurements.

Every .3D file created can then be easily and efficiently shared with users across the collaborative enterprise, without distributing original CAD files and without recipients needing system access or training.

The JT format promoted by UGS is a newish form of neutral format which is becoming popular in the automotive and aerospace industries. JT is a convenient neutral file format in a UG-NX context and it has also worked quite well in other circumstances.

In the very early days the only information in the JT file was tessellated (approximate surface data). It is now possible to have a JT file that contains tessellated information and B-Rep data (accurate solid model data). If the trend towards JT arises from a predilection for compact neutral file formats there are other competitive formats that are more compact like 3D XML; the alternate strategy being championed by IBM/Dassault (CATIA).

In some respects the rivalry between JT and 3D XML could be regarded as a beauty contest between Unigraphics and IBM/Dassault.

There is yet a third format, Product View from PTC, that does more or less the same thing. This comes from PVS (Product Visualisation Software) from Computervision which evolved with the acquisition of Division into DVise and this subsequently evolved into ProductView

‘One of the things that JT and others will do is to allow OEMs to distribute a common file format from their organisation to their supply chain,’ said Trevor Leeson of Data Translation specialists Theorem Solutions.

‘It will allow supply chain to acquire low-cost viewers as long as JT is treated just like an intelligent 3D drawing rather than being something that they attempt to do anything with.’

If the strategy is to eventually remove the 2D drawing from the process and migrate to a ‘minimum’ documentation concept of a master CAD model with 3D annotation then the JT format has practical benefits. Facilities like it are also available from companies such as Cimmetry, Proficiency, Rasterex, Informative Graphics.

Others, such as SolidWorks, offer e-drawings, while Adobe offers 3D PDF variations on the compact data format theme.

If you base your choice on popularity alone, Adobe’s PDF — whose reading software is everywhere and must number hundreds of millions of copies worldwide — is the clear winner. Through exposure to some of the more demanding customers Adobe has championed the standard-body route, working with key industries to get PDF — or variants, like PDF/E (Engineering), PDF/A (Archive), both subsets of the full PDF format — accepted as industry standards.

Out of all the formats it is undoubtedly the most flexible, being capable of encapsulating most types of digital document within the PDF wrapper — although compared with ‘CAD’ publishing formats such as DWF or 3D XML, it’s not as accurate, lightweight or 3D.

But Adobe addresses some of these issues in the recently-launched Acrobat 7, which as well as being able to handle 3D also introduces some unique capabilities.