PDF[portable document format] was first developed by Adobe in 1992 as an electronic replacement for paper. When it first came out, we were pretty puzzled by it, because laser printers did a great job, thank you very much. Now, of course, PDF gets used for "everything," even CAD drawings.
In 2004, Adobe added 3D capabilities to Acrobat v7, and in 2008 PDF became an international standard through the ISO. I spoke with Phil Spreier to learn more about the history and functioning of 3D PDFs. He is the technical director of the 3D PDF Consortium, a non-profit organization founded in 2010 to promote the use of 3D PDF.
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Q: Why did Adobe add 3D to PDF? A: At the time they were looking at more vertical markets for Acrobat and Reader. They saw that PDF was very popular for drawing and sharing, and on the Internet. Adobe wanted get deeper into geospatial and engineering, and so they needed some kind of 3D system in PDF. They standardized it right away, calling it PDF/E.
Q: When they added 3D to PDF, they used a nearly-unknown format called U3D. A: That's right, the first 3D file format was U3D -- short for "universal 3D." It was developed by 3D Industry Forum (Intel, Boeing, HP, Adobe Systems, Bentley Systems, Right Hemisphere, and others), and meant specifically for engineering. But it was more a visual representation, and so lacked CAD data like geometry, topology, PMI [product manufacturing information], and real text. When a 3D CAD model is converted to U3D, everything becomes a mesh or a line; there is, for example, no text entity in a U3D file, and so text cannot be searched or edited.
Q: U3D didn't work out well, so what happened next? A: Adobe acquired TTF, who had an interoperability format called PRC [product representation compact]. It could hold 3D data structures from any CAD system: text, PMI, geometry -- it handled all the things that U3D could not. Both U3D and PRC have metadata structures, and in practice PRC is used primarily for visualization. Companies like TS3D and Datajut have toolkits that can be used to edit PRC. So Adobe added it to the PDF format.
Today, 3D data is stored in PDFs with either the U3D or PRC format: the one you end up with depends on what the CAD program outputs. In most cases, users don't even know which one is output. It turns out they are about evenly divided in terms of product support, but highly weighted for PRC in number of users:
U3D [older] – Solid Edge, Creo
PRC [newer] – Inventor, Solidworks
Q: Then Adobe lost interest in engineering... A: There was the 2009 economic collapse, and so Adobe decided to spin-off all vertical PDF products as a cost-saving measure. The core technologies are still in Acrobat for viewing and marking up. Adobe has few products that author 3D PDF. Version 9 of Acrobat 9 was the first to handle PRC, but the last version to author 3D PDFs. Photoshop still exports 3D PDF, because it outputs to 3D printing.
Pre-COFES Conference on C3D Modeling Kernel
C3D Labs is holding a free conference on the first day of COFES.
Keynote speaker is ASCON Group CEO Max Bogdanov.
C3D Labs develops the C3D Toolkit, with modules for 3D geometry, 3D constraints, rendering, and import/export. It has been used for 20 years by the KOMPASS-3D MCAD program, and is now licensed by more than 20 other CAD/CAM/CAE vendors and is available through the Open Design Alliance.
Q: The next versions of PDF are PDF 2.0 and 3.0. What will be in them? A: PDF 2.0 adds PRC officially; until now, PRC was an extension to PDF. This is important from a standards perspective, because then PDF can be used for archiving engineering drawings.
We are just now formulating PDF 3.0. The PDF Association is working on a proposal for Web-based technology. Anyone can provide input to the format; we listen to end users of all CAD systems.
Q: Are you involved in the translation from CAD to PRC? A: Not our consortium, although we have members who provide translators, APIs, and SDKs.
Translation is very technical. It is not easy to understand because of the complex algorithms used for compression and so on. In our standards work, we are working on making it easier to figure out the PRC documentation. PRC is very easy when you license an API from TechSoft, DataKit, or Open Design Alliance. There are some open source translators, but they tend to output to U3D.
Q: Some CAD programs now import PDF files, converting the text and vector entities into native CAD objects. What's your thought on importing PDF? A: We think it is great. It is a feature that is highly requested by customers of CAD vendors. For now, only 2D drawings can be converted; the 3D content from PDF files is not imported. 3D is primarily used in a PDF document to communicate; it is not used very often as an interoperability [translation] format.
Q: Wasn't PDF meant to be read-only? A: I don't think it was meant to be read-only; it was meant to replace paper, so it could be marked up, edited, and so on. There are ways to edit PDF files, for sure, but there are also ways to prevent them from being edited.
Q: Is there is #2 use for 3D PDF? A: Its biggest use-case is in engineering documentation, as in MBD [model-based design] -- the marrying of 3D with standard digital 2D "paper" -- BOMs, assembly instructions. It is becoming more than 3D visualization, it is for communicating.
MBD tries to eliminate 2D drawings, so that everything from inspection to sign-off sheets are in the 3D. PDF is great for this, because it is based on documents: a single file holds all documentation, the 3D model, and a link to the actual CAD file -- better than Excel or ZIP -- in a file format read by everyone.
[To explain, Mr Spreier showed me some models exported from Solidworks. See figure 1.]
Figure 1 3D model exported from Solidworks to Acrobat Pro
With a 3D model in a PDF document, we can measure, markup, browse the product structure, take cross-sections, look at and change properties, and place snap-enabled dimensioning aligned with the view. When aligned to, say, the front view, then all PMIs not aligned to the front view are hidden. (See figure 2.) When views are saved, other non-technical people can access exactly the same view and see what we see.
Figure 2 PMIs displayed by Acrobat Pro
PDFs can include animations that show the installation or construction steps.
Q: PDF is not like DWG, which is a de facto standard but is changed constantly by Autodesk. A: PDF is changing very slowly, which is a blessing and a curse! When you are writing records, this is important. PDF is persistent, which is why it is used for contracts and forms -- it will always be around. And you don't have to use Acrobat Reader. There are many options. In the architectural world, Bluebeam is used a lot. http://www.3dpdfconsortium.org/
And One More Thing...
Following a six-month beta, Cloud Invent is releasing a commercial version of Cheetah Solver for AutoCAD, a plug-in that replaces the built-in 2D coinstraints and parametrics of AutoCAD 2016- 2018. It's meant to perform more efficient sketching, design modification, and motion simulation.
Cheetah also runs on Autodesk's Forge Platform. Cloud Invent is working on a 3D version of the parametric modeler, and adapting the solver to other CAD systems.
There is more at our WorldCAD Accessblog about the CAD industry, tips on using hardware and software, and our popular travelogues. You can keep up with the blog through its RSS feed and email alert service. These are some of the articles that appeared on WorldCAD Access during the last week:
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upFront.eZine (@upFronteZine) Mar 7:: How @autodesk views perpetual license holders: "There's about 2.2 million active people using our software that aren't paying us..."
Letters to the Editor
Re: Autodesk Subscriptions
Regarding the following comment from David S: "I have no desire to get continually ripped off by Autodesk. Have to find an alternative as I run a small 3-man company."
Not to be rude, but I would venture to say that Autodesk doesn't want you either. They want a steady stream of income, which customers like you were probably not giving them anyway. - R.M.
The editor replies: It must be a wonderful time to be an Autodesk competitor.
Re: Did Autodesk's near-monoculture bring down its cloud services
"Lowering profits"? "Increasing losses"? The folks at the helm of Autodesk are hired specifically to prevent this from happening. Often, they even have no experience with the products sold by the company they run.
No, the solution to better cloud reliability will not be any sort of decrease of company revenues in any direction. The only solution will be higher fees from paying users. Become a shareholder, see the glass as 90% full, and feel the Zen calm of consistently profitable quarters year over year. - Peter in Maryland (via WorldCAD Access)
The editor replies: Speaking with financial analysts earlier this month, Autodesk's co-CEOs suggested they might be raising pricing on subscriptions a few years from now.
Re: How much power does a USB outlet give your phone?
I love Ampere! Did you happen to test different cables? I found that USB 2.0 cables vary greatly in how much power they deliver. I just tossed all of my USB cables and bought high quality cables from Amazon and saw a huge improvement in charger output. I think cables tested for Quick Charge 2.0 worked best. - Eric Allen
The editor replies: I tested a fat and a thin USB2 cable, and found no difference between them. OTOH, I was using an adapter cable between USB ports and USB-C, and maybe it had an influence on my tests.
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