Earthbound Architectural Illustrations

Google Earth helps company win A/E design business

Greg Hamilton, a 3D illustrator at the A/E (architectural/engineering) design firm Durrant, remembered the day he discovered Earth -- Google Earth, the search engine giant’s terrain-exploration program.

Fascinated, he entered the coordinates for Durrant’s Minneapolis office. Almost immediately, the recognizable pentagonal rooftop of his office appeared in the program’s display window. He tried to identify his car and his colleagues in the parking lot and on nearby streets. Afterward, without ever leaving their chairs, he and Tim Heitman, Durrant’s graphics design manager, went on several domestic and overseas tours, dropping into the campuses of their old high schools and shuttling between Asia and Europe.

It didn’t take long for them to realize that what they were looking at could be incorporated into their design work.

Reshaping Downtown

At the time, Durrant was competing against several other design firms for the business of a potential client who was planning a mixed-use building in downtown Minneapolis, with retail storefronts on the ground floor and residential and business units on others. As Hamilton recalled, someone proposed putting the model into Google Earth so the client could see how the complex would look sitting next to adjacent buildings. (Note: A free version of Google Earth is available for personal and recreational use; Durrant uses the professional version, Google Earth Pro [$400].)

Though Google Earth’s free geospatial database encompasses the entire world, only select regions are viewable in high-resolution data. Minneapolis is one of the major U.S. cities available in resolution as high as 1 foot per pixel (as of August 2005). Hamilton took the proposed building’s footprint provided by the client, created a massing model that showed the building’s geometric construct and then planted it in Google Earth Pro exactly where it would be constructed. Additional rendering and animation sealed the deal. The project is now in the design phase, with Durrant’s designers refining the sketches.

Two Ways to Drop into Earth

In creating the massing model, Hamilton used Autodesk Architectural Desktop for the floor plates and Autodesk Viz for extrusion. To import the model into Google Earth Pro, he initially used Avatech Earth Connector, a Google Earth plugin for AutoCAD, but found that the imported faces were triangulated. So he looked for alternatives and found the Google Earth plugin for SketchUp. This plugin allows SketchUp users to export architectural models into Google Earth’s environment. Hamilton resorted to a more circuitous route -- he brought the massing model into SketchUp first and then exported it into Google Earth Pro.

Matt Mason, Avatech’s director of research and development, explained, “Earth Connector for AutoCAD works with triangular representations of 3D faces, so if you turn the edges on (they are not on by default), you may see some triangulation. However, we’ve found the vast majority of the users leave the edges turned off. Our upcoming release of Earth Connector for AutoCAD will address this issue. This issue is specific to AutoCAD only.”

Avatech has recruited Hamilton to help test Earth Connector for AutoCAD as well as another plugin that's in development for Autodesk Revit. Earth Connector for AutoCAD works with AutoCAD 2005- and 2006-based products.

Greg Hamilton, a 3D illustrator from A/E design firm Durrant, imported a massing model from Revit into a Chicago cityscape using Avatech’s Earth Connector plugin. With this method, Durrant can show, for example, how a client’s canopy work will look alongside existing buildings.

Location and Orientation

Designers face two principal concerns in exporting CAD models into Google Earth: making sure the model appears at the right location (correct latitude and longitude) and making sure it faces the right direction (orientation). The latest version of the SketchUp plugin accommodates this by letting a user grab a view of the terrain on display in Google Earth with the Get Current View button, directly from SketchUp’s interface. Provided SketchUp is the principal design tool, the most sensible workflow is to navigate to the planned construction site using Google Earth, acquire the satellite imagery of the site via SketchUp and then further develop the design on top of the site photo.

The option to import the site photo into the design authoring environment makes it relatively easy for a designer to keep the model’s dimensions and orientation within the confines of the project coordinates. During the design process, the Place Model button lets the user periodically preview how the model will appear in Google Earth.

Avatech’s Earth Connector facilitates this process through the ExtractKML command, which is added to AutoCAD after installing the plugin and completing some preparatory work as outlined in Avatech’s tutorial. A user can obtain project coordinates by navigating to the project site in Google Earth, putting a place marker at the location and then saving the location of the place maker as a KML file. In the same way, a user may pick a second coordinate to serve as the direction of the y-axis -- this coordinate determines the orientation of the model. Afterward, when the ExtractKML command is invoked, a wizard prompts the user to import the two place marker locations to georeference the model. Avatech’s Mason pointed out, “Using a separately specified place marker to set the orientation is a method that is very rarely used. The vast majority of people use the easier mechanism of compass degrees, or in the case of Revit users, the ‘Project North’ option.”

Blurring and Tilting the World

Because Google Earth currently doesn’t offer high-resolution imagery for all cities, Hamilton and his colleagues at Durrant have developed an ingenious workaround. When the project site happens to fall into a low-resolution region, or when they must use screen shots from Google Earth Pro as backdrops for high-resolution printing, they import the image into Adobe Photoshop and apply one of the blur filters. The blurred background, as it turns out, not only disguises the otherwise noticeable pixelation but also simulates depth of field by allowing models in the foreground to appear more prominent.

To give the client a view of Zini Island during daytime and nighttime, Hamilton and his colleagues imported the project into Google Earth. For nighttime lighting simulation, Durrant’s illustrator Chris Medeck created the glowing effects in Autodesk Viz, then added the pin lights and darkened the view in Adobe Photoshop.

Google Earth allows users to tilt and rotate the landscape, so Hamilton and his colleagues grab isometric views of the 3D topology from Google Earth, match it with a tilted view or camera angle in a CAD application and then consolidate the two by overlaying one on the other. In a recent project involving a cross-section of a Chinese community adjacent to the city of Xiamen, Hamilton used the same method to generate the necessary presentation materials.

Downloads and Information

• Download for free the SketchUp 5 3D modeler and its companion Google Earth plugin.
• Download the free Avatech’s Earth Connector from the Avatech Web site.
• For more about Earth Connector, read “Avatech’s AutoCAD Google Earth Connector” by Dennis Wuthrich (Geospatial Solutions, March 2006).

Editor's note: This article was updated online May 30, 2006, to reflect Durrant's use of Google Earth Pro version.