Photosynth.net, a fairly new Web site from Live Labs, Microsoft's applied research arm, automatically stitches together your digital photographs to create a somewhat abstract but high-resolution three-dimensional re-creation (dubbed a synth) for the world to explore. The 3D photo reconstructions suggest the improbable offspring of a David Hockney collage, Apple's QuickTime VR, and Microsoft Research's excellent WorldWide Telescope. In any event, it's one of the more mind-blowing things to appear on the Web since Google Earth.

Ready-made examples of Photosynth in action have been previewable for several months now, but Photosynth.net allows any visitor to upload photos--up to 20GB worth, to be precise to create a 3D Web installation. To use Photosynth.net, you must first install two small apps: a browser plug-in that supports Firefox 2 or 3 and Internet Explorer 7; and the free Photosynth desktop application for uploading photos. You'll also need to use Windows XP or Windows Vista as your operating system, and have a PC configured with at least 256MB of RAM (1GB is recommended) and at least 32MB of graphics memory. Mac users who wish to try the site can run it under Boot Camp, but OS X isn't supported (yet...), nor is Parallels (VMware Fusion 2.0 is reported to work).

Creating your own synth starts with capturing a bunch of suitable photos; Microsoft provides an excellent primer on this. The basics: Capture JPEG images only (of unlimited size); try to overlap your shots by about 50 percent; start with a wide panoramic shot before moving in for greater detail; ensure that all photos are oriented correctly; and limit the angles between photos.

The desktop software analyzes your photos and uploads them to Photosynth.net, which then creates the synth automatically. The more suitable your shots are, the more coordinates Photosynth can refer to in reconstructing the scene (3D designers will be familiar with this "point cloud" concept). The more points you have, the more "synthy" your collection will be.

A quick note on copyright: Since all synths are public at the moment, it's good to see that you can fully--or partially--restrict the reuse of your photos through a full spectrum of Creative Commons license options.

Uploading a simple 10-photo synth takes a matter of minutes. I went a little more extreme and uploaded a 156-photo collection of Red's Java House by San Francisco Bay to test the software's powers of reconstruction. My collection (amounting to 214MB of 2048-by-1536-resolution shots) took about 75 minutes to upload and was immediately available as a synth. Impressive.

Community features play a big role on Photosynth.net, and Microsoft expects that role to grow. You can easily write captions and keyword tags for your photos and use Virtual Earth to geo-tag your collection (though this feature was a bit sluggish when I tried it). For synths created by other users, you can post comments and flag inappropriate content. To share any synth with a friend, use a unique direct-link URL or copy the synth's embed code and add it directly to your blog.

For visitors looking for inspiration, Photosynth has some dazzling collections that they can dive into right away, thanks to such early testers and partners as National Geographic and NASA. Among my favorite synths are ones of the Piazza San Marco, the Machu Picchu ruins, Venice's Grand Canal, the Taj Mahal, Grassi Lakes, Stonehenge, the U.S. National Archives, and Dale Chihuly glass sculpture exhibits. You wouldn't ber able to see some of the detail shown in the latter three collections even if you were there in person.

When viewing a synth, you can click an icon on the bottom-right to have the synth occupy your entire browser window. You can improve the view further by using your F11 function key to set your browser to full-screen mode. You also can zoom in and out with your mouse wheel; the zoom area is based on your mouse location. The tilde (~) key toggles the grid view mode, which allows you to see the entire photo collection that forms any synth; the spacebar lets you jump to the next photo in the spatial tour.

Is Photosynth.net a beta? Call it a work-in-progress, the Web site recommends: "What you see on this site is the first of many versions of Photosynth. Call it beta, call it 1.0, call it whatever you want... just know we are hard at work adding support for more browsers, more platforms, and more hardware, and just making the experience that much more amazing."

The nimble Photosynth team definitely has some interesting things it wants to explore. Think possible Mac and Flickr support, groups, favorites, RSS feeds, scripted tours, private synths, greater Virtual Earth integration, and an open API for mashups. Then there's the game-changing feature of cross-linking between the synths of various users or even of combining photos of the same place--taken by different people at different times--into one giant supersynth to rule them all.