Google has deployed aerial photographers to fly over scores of cities at low altitude, taking pictures of each neighborhood from many angles. For any given building in these well-documented cities, Google is likely to have photos snapped from at least six different angles. Once you decide which building you want to model, Building Maker starts out by presenting you with a picture from one of these angles. In the first step in the model-building process, the program places an outline of a 3-D box over the photo, and your job is simply to drag the corners of the box until they match up with the corners of the building in the image.
In the easiest case—a building that’s a simple rhomboid, with a flat roof and no wings or protrusions—placing that one box and aligning the corners is almost all you need to do. The only further step is to examine and adjust your model from other angles. Because you’re working from 2-D images, you have to make sure the corners in the digital model match the corners in at least two different images before Google can know exactly where the model should go in the “three-space” of Google Earth, and what sections of the images should be applied to the sides of your model to make it look real.
Practically speaking, I found that you need to do the alignment from four, five, or six angles to get everything just right. While this may sound tricky, it’s actually quite straightforward, and will be especially easy for anyone who’s used other 3-D modeling tools such as Google Sketchup (Building Maker’s grown-up cousin) or the object creation tools in the virtual world Second Life.
Things start to get complicated—and much more interesting—when you’re modeling a more complex building. It was a lucky stroke for me that the place where I live, a building called James Court that was constructed in 2005 by a Boston-based estate developer Kenney Development, is both absent from Google Earth (meaning I could be the first to build a model of it) and has a fairly simple shape: it’s a seven-story building that forms an L-shape on the corner of Newton and Harrison Streets, near the Washington Street corridor in Boston’s South End. But it has just enough irregular features, including a step-back roof on one wing and an overhanging brow on the Newton Street facade, that I had to a learn a few of Building Maker’s more esoteric tricks, such as the technique for creating new boxes and attaching them to existing ones, to make the model come out right.
As a historical aside, James Court is in a neighborhood that has gone through an incredible transformation over the last two decades. Washington Street runs along the narrow neck of land that, for centuries, was Boston’s only connection to the mainland. In the 1800s, the tidal flats on either side were gradually filled in to create room for
