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This tutorial deals only with exporting and importing models created with Googles Building Maker tool into third party 3D applications such as Blender 3D. For more details on using Googles Building Maker itself click here to watch the online tutorial.
Follow the directions here to make an actual building model based on the images and photographs available from Google Earth. Sign in to your Google Account (or create one if one is not available) and save the file. Once done Google Building Maker will load a page that has a couple of options to 'edit' the object, either using Building Maker itself or using SketchUp; select the SketchUp option will sign you into and take you to a Google 3D Warehouse page (it will automatically be created for you if one doesn't exist) similar to the one shown below - the model or models will be shown in a preview window (static).
Click the "Download Model" button and then click either/or/both of the options to save the file as Google Earth 4 *.kmz or Collada 1.4 file (the assets for the Collada file are saved within a ZIP file).
If you saved to the Google Earth *.kmz format you'll need to do another couple of steps to 'extract' the files from the *.kmz before they can be used in any third party 3D app's other than Google's SketchUp. Read how to convert SketchUp files for use here. Saving the Collada file simply means extracting the contents of the ZIP file to your hard-drive.
Once one or the other has been done you'll note that both make use the *.dae format, which Blender can import directly. So, open Blender and from the file menu select "File >> Import >> Collada 1.4 (.dae)", browse to the file and click the "Import and Exit" button. After a few seconds the file will appear in Blender. Press "Alt+Z" to see the textured model (the materials and textures should be automatically imported, set-up and applied to the mesh). Done!.
Models are aggressively optimised so they'll need to be converted back into 'faces' ('quads') before any further editing is done, select triangles as pairs of faces or select the entire mesh and press "Alt+J" - note that due to the nature of the polygon optimisation this may result in quads that are at odd angles across faces which 'break' potential edge-loop lines.
Also bear in mind that the UVW and texture maps aren't quite as optimised as they would be if done manually so if any additional editing is done it's likely that you'll need to re-task and re-apply the texture so it fits correctly over the newly edited mesh. Also note that textures used on the original models are pulled from several photographs that will have different perspective points.
If using the textures create using Building Maker check through google's terms and conditions to make sure the appropriate Copyright Notice is available, this is especially so for models you intend to distribute outside of Google user generated content system or commercially.