3D Photorealistic Modeling Using Geobrowsers (Spatial Tech Column)1 May, 2007 By: James L. Sipes
Design for the world while sitting at your computer.
When geobrowsers such as Google Earth, Microsoft Virtual Earth and NASA's WorldWind were introduced, they provided a new, exciting way to view our world. They gave us a quick, efficient and easy-to-use interface for linking satellite imagery, maps, terrain, 3D buildings and other geospatial information. Many professionals who work with geospatial data realized that these geobrowsers could be effective visualization tools for sharing information because anyone with an Internet connection could use them.
As the next generation of geobrowsers develops, expectations have increased, and users are demanding access to more information, greater accuracy and realism and interactivity.
Resolution and Detail
The current geobrowsers have updated information all over the globe, and image resolution and terrain detail have improved significantly in many areas. Google Earth, which uses Digital Globe imagery, now has a resolution of at least 15 meters for most regions, with many areas being much better. Most populated sections of this country have a resolution of 0.3–1 meter, and areas such as Las Vegas, Nevada, have a resolution of 15 cm (6 inches).
Some areas are still available only in low-resolution imagery. Oceans, areas around the Arctic and Antarctic and other fairly desolate areas have much lower resolution. Some areas in South America and a number of islands, for example, have a resolution of approximately 500 meters.
Google has worked very hard during the past year or so to resolve some of the inaccuracies in Google Earth. Vector-based data such as boundaries, roads and bodies of water produced several problems.
Another issue is that the images are not all taken at the same time. If you look up the area near New Orleans, you can still see images that were taken before Hurricane Katrina. The Google images of Atlanta, where I live, are at least three years old, and my home still isn't on the map.
As the level of detail increases, so does the concern about security issues. In some locations, such as the U.S. vice president's home, Google has intentionally blurred the images. This issue will continue to become more important as image quality increases in tandem with the concerns about terrorism.
Virtually all geobrowsers can display 3D buildings, but earlier versions had a major constraint in that these buildings were simply geometric shapes that looked like wooden blocks. Many geobrowsers now allow a much greater level of detail in building geometry and display textures. Microsoft Virtual Earth 3D (VE3D) includes textured 3D buildings for several major cities, and although this falls far short of being photorealistic, it's a huge step in the right direction (figure 1).
Figure 1. A view of downtown Atlanta generated by Microsoft Virtual Earth 3D.
One significant improvement in Google Earth is that it now supports COLLADA (collaborative design activity) 3D objects. COLLADA defines an XML-based schema to make it easy to transport 3D designs between applications. With this capability, users can create highly detailed 3D models with textures using popular 3D modeling programs such as SketchUp, 3D Max and Maya; save them in a COLLADA format; and then import them into Google Earth. Users even can use a drag-and-drop approach, so it's an amazingly simple process.
Creating 3D Buildings
Last year Google purchased the SketchUp suite to provide tools for creating more detailed 3D objects. Google SketchUp and SketchUp Pro are powerful, easy-to-use 3D modeling software tools for designing buildings and other site features.
A Google plug-in gives SketchUp the ability to interact with Google Earth. This plug-in allows users to read and write Google Earth model files in the KMZ format and to take 2D and 3D snapshots from Google Earth. The plug-in also lets users share SketchUp models with the SketchUp community using the new 3D Warehouse library (figure 2). 3D Warehouse is a collection of 3D buildings and other 3D content created and shared by Google Sketch-Up users. Using 3D Warehouse, designers can search, download or share 3D models that they have created.
Figure 2. Las Vegas' Venetian Hotel-Resort-Casino, as it exists in Google Earth's 3D Warehouse.
Several plug-ins for SketchUp help improve graphic quality. The RPS Ray Trace Exporter creates photorealistic renderings from SketchUp models using the AccuRender ray-tracing engine. SU Podium can create photorealistic renderings within SketchUp by using features such as textures, background colors, groups and shadows. The SPIRIT plug-in allows materials and textures assigned to a model in SketchUp to be rendered in Fresco II, in which light sources and high-quality procedural textures can be added to enhance realism.
SketchUp also includes component libraries of 3D models for architecture, construction, landscape architecture, mechanical design, transportation and other features. Users can add textures to 3D models from a materials library.
Google Earth's terrain model was created from NASA's SRTM (Shuttle Radar Topography Mission) and augmented with digital elevation model data to fill in the gaps. Google has been working to increase the detail of terrain in selected areas. For example, the terrain for Mt. St. Helens, Washington, has been updated to a high-resolution terrain with 3-meter resolution (figure 3).
Figure 3. The terrain models have been improved considerably from earlier versions of Google Earth. For example, this image of Mt. St. Helens, Washington, now features high-resolution terrain with 3-meter resolution.
It's also possible to integrate LIDAR (light detection and ranging) data into Google Earth. 3D Nature has an example on its Web site in which it created an enhanced version of the Red Rock Amphitheater in Morrison, Colorado, using high-resolution LIDAR data draped with imagery using Scene Express.
Another tool that can create 3D imagery for inclusion in Google Earth, Scene Express provides KML authoring tools for 3D Nature's Visual Nature Studio and World Construction Set (figure 4). Scene Express includes an exporter for creating landscapes in KML/KMZ format for use in Google Earth and other KML-compliant applications such as ArcGIS Explorer and NASA's WorldWind. Scene Express simplifies the process of creating detailed, photorealistic landscape models and then linking the models to geospatial data.
Figure 4. A 3D model of a golf course created using 3D Nature's Visual Nature Studio and World Construction Set.
Google Earth still doesn't support animation, shaders or physics, but most experts predict it's only a matter of time before these features are included. When that happens, the level of realism and interactivity will go up another notch. This capability also will create new opportunities for game developers, who seem to be the most innovative when it comes to producing interactive graphics that tie into Google Earth.
In this article
James L. Sipes is a senior associate with EDAW in Atlanta, Georgia, and the founding principal of Sand County Studios in Seattle, Washington. Reach him at firstname.lastname@example.org.
About the Author: James L. Sipes
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