3D PDFS…

4 thoughts on “3D PDFS…”

1. jepler says:

   January 23rd, 2006 at 8:46 pm

   My employer decided to jump on the pdf/u3d bandwagon about 9 months ago. Here’s what I learned from the experience:

   • The spec, while freely available, was poorly written. In one case (a scheme for encoding integers) the normative part of the document and the sample implementation were different—and when I followed the Normative part, the viewer I had access to wouldn’t show the files. A subsequent release of the u3d standard did not correct this. I still don’t understand how this encoding scheme works, I simply transcribed the sample implementation to my project’s language and hoped for the best.
   • Intel provided extensive “open source” code implementing the standard, but it wouldn’t compile, even when built with their special version of the cygwin compiler for windows. Several bits didn’t look like they could possibly even be C++. The “open source” implementation includes incompatible implementations of something-like-COM and something-like-STL. It doesn’t build on Unix, either.
   • The one standalone viewer I had access to only worked on Windows 2000 and up (my Windows machine was NT4 at the time). While the standard says that all viewers must support uncompressed files, the viewer seemed to fail on all uncompressed files, and require compressed files. I’m told this is the same viewer that is embedded in Adobe viewer.
   • Only the Windows version of Adobe Viewer supports the embedded objects, and only for Windows 2000 and up. Once again, Unix users need not apply.
   • Not only doesn’t the spec doesn’t really specify how lit surfaces work (am I supposed to simply know that the implementation happens to work like OpenGL—or, even worse, Direct3D?), but Adobe and the standalone viewer give very different results (nope, I guess it’s not as simple as “like OpenGL”). Adobe also gives different initial viewpoints and viewports (they’re specified in the pdf file, even though they’re also specified in the u3d file).
   • While the standard supports lots of complicated stuff, like skeletal animations, this is not very relevant to the kind of work we’re doing (I think this is left over from when they wanted it to be a 3D flash replacement, not some kind of engineering data exchange format). Don’t worry—buried nearly inaccessibly somewhere on Adobe’s site is an incredibly terse list of what elements they support. It’s in a PDF file, of course. If you ask google the right thing, it’ll give you the page.
   • What, you want to get the model back out of the pdf file and into a format your cad package supports? Forget it. First it’s tough to get it out of the pdf, but then you’re still stuck with this useless “u3d” file. Well, I guess all the people you want to exchange the documents with can also buy a new $1000 application to read your files.

   I did succeed in writing an exporter that worked (modulo lighting and initial camera position) in adobe viewer, without paying a dime to anybody, but it was pretty hellish time at the office.

   This has been more or less forgotten since the day last fall we showed it at a conference (and it went OK as a demo, but I don’t think the crowd was that impressed with the technology). I’m dreading the day my supervisor turns up and asks me to get back to work on it.

2. 3dexplorer says:

   September 7th, 2006 at 1:08 am

   About 3D PDF generation…
   The Acrobat3D package is a little pricey, but fills a gap of a 3D file conversion and 3D PDF authoring tool. However, what happens if you have your own applications with 3D data – are you going to force all users to buy copies of Acrobat3D just to create 3D PDF content? It’s just possible, with considerable work to write your own U3D files, but then you’ve got to use some other package to embed 3D content into the PDF format.
   I just noticed PDF3D (www.pdf3d.co.uk) which appears to offer program development tool that simplifies writing 3D PDF generation in custom applications. It’s not free, but looks like it takes the hassle out of the job.

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