MCAD Tech News #184

15 Aug, 2006 By: Jeffrey Rowe

In part one of this series, I discussed that while a truly neutral design data format for reusing CAD assets has been attempted several times, it’s still far from being realized. Over the years, several organizations have tried to develop neutral design data formats with varying degrees of success. Last week, I covered UGS’ JT Open initiative and this week I’ll look at the Web 3D Consortium’s X3D and CDF (CAD Distillation Format).

Distill CAD Data with CDF

A couple of years ago, the CAD Working Group of the Web3D Consortium completed the first working draft of the CDF specification -- an open, royalty-free file format that distills the essential elements of complex CAD data for use throughout an enterprise. The intent was to enable translation of CAD data to an open format for publishing and interactive media. CDF allows the use of CAD data in documentation, training, sales and marketing departments -- without exposing sensitive design information (such as dimensions and physical properties). The process includes an open framework pipeline that incorporates tools for decimation of surfaces to constructs that are more common in non-CAD environments.

The CDF specification is based on X3D, an open, extensible standard for communicating 3D data, which is now in the final stages of ratification by the ISO (International Organization for Standardization). The ratification process continues to move along smoothly, and it should become a formally recognized ISO standard by the end of this year.

Billions of dollars are invested in CAD data, but that data is trapped within a myriad proprietary formats and specialized CAD systems that prevent its use within or outside of the engineering department. CDF unlocks this huge, untapped resource while protecting proprietary design information and complementing existing design-oriented CAD formats.

CDF enables the integration of selected portions of CAD designs into common desktop applications, allowing non-CAD experts to easily repurpose design data. For example, the CAD data from a large engineering project can be transferred via CDF into PowerPoint for interactive presentations. In turn, operations could use the marketing data for creating a safety video.

Leveraging X3D -- A Key to CDF's Success

X3D is a royalty-free, ISO-ratified format for sharing 3D models, visual effects, behavioral modeling and interaction. It forms the extensible technology foundation of the Consortium's market-focused standardization activities. X3D is a powerful, open file format standard for 3D visual effects, behavioral modeling and interaction. X3D's XML-encoded scene graph enables the incorporation of 3D data into Web services architectures and distributed environments and facilitates moving 3D data between applications.

X3D is an initiative to leverage 3D as digital media as easily as text and 2D graphics. It provides the technology for viewing, modifying, customizing and reusing 3D visualizations for other applications.

X3D provides XML encoding so that interactive 3D and multimedia content can be read or written using standard XML tools and can be integrated into any XML-enabled application or Web service. Because X3D is an open XML standard, it’s not dependent on the continued existence of any one organization. Visual assets exported to or created in X3D are ensured to be usable in the future.

Because it’s extensible, developers can exploit X3D component architecture and XML schema to implement it in their own applications or extend and customize the schema to add vertical market-specific capabilities or custom data to the format. I spoke briefly with Dr. Julian Gomez, chairman of the CAD Working Group of the Web3D Consortium, and he emphasized that in the future the organization would like to create vertical extensions to CDF in specific domains, such as MCAD, AEC, medical devices and the like.

X3D lets users share 3D data in a lightweight format. The binary encoding offers extreme compression while preserving geometry and is therefore well suited for networked 3D consumption. File sizes are as much as 90% smaller than those of existing formats, so users can rapidly load and transfer them via the Web or cell phones for use in real-time collaborative systems. Finally, X3D provides an interchange format for integrated 3D graphics and multimedia that lets content producers to share 3D, interactivity and physics between applications.

Earlier this month, the Web3D Consortium announced that it had submitted a revision of the X3D specification for review by the ISO. This X3D revision is the second update to the X3D specification since its unanimous approval as an international standard by ISO in 2004. It represents a significant advance in layering and overlays, physics, particle systems, smooth motion and picking, enabling 3D simulations and Web applications to implement features traditionally found only in high-level gaming systems.

How X3D and CDF Measure Up

X3D and CDF are examples of more attempts at developing a neutral CAD data format for viewing and other purposes that don’t require a product or technology from the company from which the data originated.

Because CDF is X3D-based, it’s focused on describing data and in no way competes with or duplicates the efforts of STEP or IGES. The sole purpose of CDF is distilling the visual aspects of CAD model into what are termed, a “subtle” format, that retains some assembly and subassembly information, but not so much that the design data could be imported into a mechanical CAD package and used. CDF also contrasts with the monolithic nature of VRML that requires adopting an entire feature set for compliance. X3D, on the other hand, lets developers support subsets of the specification (Profiles) that are composed of modular blocks of functionality (Components).

A component-based architecture supports the creation of different profiles that can be individually supported. Components can be individually extended or modified through adding new levels, or new components can be added to introduce new features, such as streaming. Through this mechanism, advancements of the specification can move quickly because development in one area doesn't slow the specification as a whole. Importantly, the conformance requirements for a particular piece of content are unambiguously defined by indicating the profiles, components and levels required by that content. X3D and CDF are about to make forays into mechanical CAD, AEC, GIS, medical markets and others may be on the horizon. Those areas include a lot of vertical markets, but then they all depend on a lot of visual data that could be handled by X3D and CDF.

Author’s Note: In the near future, I’ll look at Dassault Systemes’ 3D XML and Intel’s Universal 3D Standard and associated 3DIF (3D Industry Forum).