Computer Graphics World

3D Printing•Architecture n n n n Model Making Munson began the modeling process by gath- ering vital information, including 2D satel- lite imagery, Google Earth data, photographs (both personal and those downloaded from the Internet), publicly available 3D models, and Wikipedia entries, among others. He then used Autodesk 3ds Max Design software, where he wrote the files required for the 3D printing—a time-consuming process. In ad- dition to 3ds Max Design, Munson also used Autodesk's AutoCAD, Google's SketchUp, and Adobe's Photoshop as part of his tool kit. Another obstacle: The data came in a vari- ety of formats. Also, it originated from a num- ber of sources, so all the information had to be cross-checked. According to Munson, he tried to obtain two to three sources for every could be output by the printer, a Z Corp. ZPrinter 650. Another source of information resulted from the use of photogrammetry—extracting 3D information from flat 2D photos through the use of points. "I used photos for more than just applying the textures on the models," Munson says. Yet, the photo textures were aes- thetically important to the project, bringing the area to life in a way that a colorless print cannot do. Some of the digital reference models did not have textures, while others did but had to be reapplied. "One thing about 3D printing is that you cannot have shaders, so I had to redefine those materials," Munson points out. "You need standard texture maps." Most of the textures used in the project were extracted elsewhere for a home for the models, finding it at the New York City Fire Museum. The mu- seum, however, wanted larger versions of the models, and with the help of Z Corp., he was able to oblige. The larger triptych, whose models each measure 17 inches square, was printed in sev- eral segments, with some of the larger struc- tures output separately to accommodate the machine's print-size envelope. "Many people don't realize that these machines can go be- yond the size of the build chamber if the user is good at hiding seams," says Munson. Although the printer reads and outputs solid models, Munson intentionally bored holes into a number of the pieces after they were printed so that the final model was less heavy. structure in the model. For the "after" model of the World Trade Center, he located LIDAR scans taken on September 16, just days after the buildings fell. However, finding informa- tion about the context (nearby) buildings was far more difficult than obtaining the data for the World Trade Center site. All told, the ma- jority of the information for the models was available for free, but on occasion Munson purchased digital Revit or SketchUp models. With all the sources in hand, he then cross- checked the graphics sources utilizing sky- scraperpage.com or by consulting Wikipedia to obtain the numerical height of the various buildings. "Had the Port Authority [bought into the project], it would have been easier because I would have had less cross-checking to do. In- stead, I had to pull data from wherever I could find it," Munson says. All those sources served as references, or a 3D template, so that Munson could re-create them as solid models in the computer so they Munson collected a great deal of architectural data pertaining to the site and then incorporated it into files within Autodesk's 3ds Max Design software, where he prepared the models so they could be printed in 3D. Often this meant cleaning up textures and re-creating the imagery as solid models. from photos, especially those used for the "af- ter" model, in which the building facades are strewn with debris. The ZPrinter 650 uses a white resin materi- al to build models through an additive process; because it supports full 24-bit color (akin to a 2D printer), it can produce a model with mil- lions of distinct colors. As a result, the physical model matched the digital version precisely. "It can be finicky, though, since you are using material IDs," Munson adds. Remembering History Eventually, Munson got everything to work, generating an initial set of triptychs, each four inches square. Setting his sights on the National September 11 Memorial Museum, Munson sent the triptych to the museum cu- rators. When it was not accepted, he looked "You just don't press a button and out comes the model," Munson explains. "There's specialized labor and craftsmanship that's in- volved. Yet, it's still a relatively fast and inex- pensive alternative to building realistic, high- end models." The larger models—whereby one inch is equivalent to 150 feet—offer a detailed, high- ly accurate look at the site. "The models show things that you don't see elsewhere," Mun- son says. "It's an accurate, 3D, fully rendered model that is reproducible. Just to see a physi- cal model of the site is really moving. It shows realism within context." It is indeed an architectural scene that we can't, we shouldn't, forget. n Karen Moltenbrey is the chief editor for October/November 2011 51 Computer Graphics W orld.

• Cover