The full Adobe Acrobat 3D program costs about $1,000, and even the upgrades from earlier versions of Adobe Professional are expensive. But Microsoft Windows users can download a 30-day free trial to experiment with, putting their 3D content into PDF. And all you need to view a model in 3D PDF is an updated copy of the free reader (also available for Macs and handheld devices) — although Adobe currently provides no 3D PDF creation software for Mac OS X.
How It Stacks Up
Viewing a 3D model is fairly straightforward. A 3D Toolbar appears after you click on the model. Click-and-dragging the mouse rotates the model, and by clicking the Arrow Cross icon, you can shift and pan. Clicking on the Home icon brings back the default view. You can choose between a variety of lighting options by clicking on the Lamp icon.
Once you get your navigational bearings, you can also take advantage of a view manager to save certain views, so subsequent navigation is not so cumbersome. One missing feature in Adobe Acrobat 3D that is found in other 3D viewing programs is an automatic spin movement.
But Adobe 3D offers some nice standard features. One is the ability to create dynamic sections through the model by clicking and dragging the mouse after toggling on the Cross Section button. A static view of any chosen section can then be saved for later viewing in either Acrobat 3D or Adobe Reader.
Another nice feature is the ability turn various parts of the model on and off via its Model Tree, so you can peel away various outer coverings to see what lies beneath.
The parts grouping is automatic, and Acrobat 3D preserves groups that exist in the model being imported. Selecting objects from within the model tree listing alone can be challenging, because object and group names are assigned automatically and only differ by number. Fortunately, you can also click on any object in the model to select it.
There is also a decent selection of viewing choices (solid, wireframe, transparent, illustration) that can give your model an interesting character. A measuring/ dimensioning feature (Distance Tool on the 3D toolbar) is available but I found it very difficult to use with any facility. In addition, dimension mark-ups cannot be saved for viewing by Adobe Reader or even in a subsequent session using Acrobat 3D.
The viewing tools by default use an "object manipulation" interface style, more optimal for viewing mechanical parts than buildings. They are pretty good, if inelegant, for moving around and viewing a model from a distance. But even with the semi-hidden "Walk" tool, producing realistic interior views is pretty challenging. Perhaps in the future Adobe could support a data flag to label models as "object type" or "world type," and provide more architecturally suitable viewing options by default for the latter.
A very useful feature not available in many other 3D tools is a text capability for adding notes in an overlay on the model for team review. Normally, this function is only for others using Acrobat 3D, but there is a setting in the comments menu ("Enable for Commenting in Adobe Reader") that will let Adobe Reader users get in on the collaboration.
Another associated but separate utility, Acrobat 3D Toolkit, lets you further edit your model by adding textures, materials, and lighting, and creating animations. Several of Adobe's sample PDF files demonstrate these features by showing engines in motion.
Exporting to 3D PDF
There are several ways to convert a CAD model to PDF, but they are not foolproof. Adobe Acrobat 3D has direct support for U3D, 3DS, DXF, OBJ, DGN, VRML IGES, 3DM, and MAX. You can drag and drop any such files into the Adobe application or right-click on the file names to pick "Convert to Adobe PDF."
Adobe's 3D Capture Utility can capture the OpenGL display data for a 3D model from another application that renders using OpenGL. To grab a model this way, launch both applications, display your model in the CAD program, then pick "From 3D Capture" from the File/Create PDF pull-down menu in Acrobat 3D. A one-time dialog box should appear telling you it has recognized whichever application you're using.
After that initialization, the Print Screen button from SketchUp, for instance, will cause the model to load in Adobe Acrobat 3D as a PDF file. For other applications such as AutoCAD, Revit, Architectural Desktop, or form-Z, check the Adobe Support Web site to find the proper settings needed to make your 3D graphics display work.
Yet another method involves using the Acrobat 3D Toolkit to import your model. This utility also imports additional file formats such as DWG. After you import the file, save it as U3D for direct import into either Acrobat 3D or Adobe Reader.
Once the 3D model is a PDF file, it can be combined with other PDF content. If you want to mix it with other document pages, simply add those additional pages in Adobe Acrobat. Perhaps more interestingly, you can compose your model with other graphics and text on the same page. Then you can insert the entire page into Microsoft Word, Excel, or PowerPoint files for resizing and arrangement with other text and graphic elements.
U3D, an Open Format
In contrast to the OpenDWG Alliance coming into existence after the DWG file format had been developed, the open U3D file format was firmly established well before Adobe released the Acrobat 3D PDF. So while the OpenDWG Alliance does its level best to reverse-engineer the DWG file format to make it available to all CAD applications, the U3D format doesn't face that hurdle.
Unlike Autodesk, which constantly modifies the DWG format to make it inscrutable to the OpenDWG Alliance, Adobe openly uses U3D as a base format to make 3D PDF accessible to software developers.
This openness is thanks to Ecma International (formerly ECMA, which stood for European Computer Manufacturers Association, but now its lower case name reflects a larger global participation). Ecma worked with the 3D Industry Forum to come up with the U3D format.
U3D consists of standardized syntax and semantics for 3D modeling and visualization for "downstream 3D CAD repurposing and visualization" — which means that everyone can share its use. Although UCD standardizes the model parts description, it does not address the rendering of that 3D content. So how a model is rendered is left open to the application developers.
Still, the fact that such a 3D standard now exists and has been put into use in the latest PDF versions by heavyweight Adobe, gives us great optimism that 3D CAD will have fewer translation problems between CAD programs than still plague 2D CAD.
So far Adobe Acrobat 3D has been slow to gather momentum, but because PDF use is so popular, I expect that, like an inexorable tide, it will eventually move all CAD boats. Sooner or later, most of the major CAD programs will include either a U3D export option or a direct PDF (3D) option. I recommend that you acquaint yourself with the basics of how Adobe Acrobat 3D operates. When the tide goes out, you don't want to see your boat beached on the rocks.
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Evan H. Shu, FAIA is an architect with Shu Associates Inc. in Melrose, Massachusetts. He is a contributor to The Architect's Handbook of Professional Practice and is publisher and editor of Cheap Tricks, a monthly newsletter for DataCAD users and computer-using architects.
This article was reprinted from the July 2006 issue of Cheap Tricks © Shu Associates Inc. with permission of the publisher.