An introduction to Microsoft’s Photosynth for generation 3D Model.

                     Photosynth is a software application from Microsoft Live Labs and the University of Washington that analyzes digital photographs and generates a three-dimensional model of the photos and a point cloud of photographed object. Pattern recognition components compare portions of images to create points, which are then compared to convert the image into a model. Users are able to view and generate their own models using a software tool available for download at the Photosynth website.

                                             Photosynth is based on Photo Tourism, a research project by University of Washington graduate student Noah Snavely. Shortly after Microsoft's acquisition of Seadragon in early 2006, that team began work on Photosynth, under the direction of Seadragon founder Blaise Aguera y Arcas.

Microsoft released a free tech preview version on November 9, 2006. Users could view models generated by Microsoft or the BBC, but not create their own models at that time. 

Microsoft teamed up with NASA on August 6, 2007 allowing users to preview its Photosynth technology showing the Space Shuttle Endeavour. On August 20, 2007, a preview showing the tiles of Endeavour during the backflip process was made available for viewing.

On August 20, 2008, Microsoft officially released Photosynth to the public, allowing users to upload their images and generate their own Photosynth models. In March, 2010 Photosynth added support for Gigapixel panoramas stitched in Microsoft ICE. The panoramas use Seadragon based technology similar to the system already used in synths.

The Photosynth technology works in two steps. The first step involves the analysis of multiple photographs taken of the same area. Each photograph is processed using an interest point detection and matching algorithm developed by Microsoft Research which is similar in function to UBC's Scale-invariant feature transform. This process identifies specific features, for example the corner of a window frame or a door handle  Features in one photograph are then compared to and matched with the same features in the other photographs. Thus photographs of the same areas are identified. By analyzing the position of matching features within each photograph, the program can identify which photographs belong on which side of others. By analyzing subtle differences in the relationships between the features (angle, distance, etc.), the program identifies the 3D position of each feature, as well as the position and angle at which each photograph was taken. This process is known scientifically as Bundle adjustment and is commonly used in the field of photogrammetry, with similar products available such as Imodeller and D-Sculptor. This first step is extremely computationally intensive, but only has to be performed once on each set of photographs.

 

The second step involves the display of and navigation through the 3D point cloud of features identified in the first step. This is done with the publicly downloadable Photosynth viewer. The viewer resides on a client computer and maintains a connection to a server that stores the original photographs. It enables a user to, among other things, see any of the photographs from their original vantage point. It incorporates DeepZoom technology Microsoft obtained through its acquisition of Seadragon in January 2006. The Seadragon technology enables smooth zooming into the high-resolution photographs without downloading them to the user's machine.

The Photosynth  based viewing software is only available to the Windows 7, Windows Vista and Windows XP operating systems. The team recently released a Silverlight version of the viewer which has succeeded the viewer as the main option to view Photosynths: Photosynth Silverlight Viewer

As of March 2009 user uploaded Photosynth collections are now available for viewing on iPhones using iSynth (3D) or Seadragon Mobile (2D only).Current generation Photosynths are easy to capture, as photographs uploaded on Photosynth can be taken by any regular digital camera or mobile phone. In general, the higher the megapixels, the clearer the pictures.

              Users have the option to geotag their digital shots on sites such as Flickr and then upload them on the online Photosynth web service. Images uploaded on Photosynth give people the ability to seamlessly view landmarks, public spaces and objects from all sides. One example of this technology in use is the Deep Earth project in which creators are developing an interactive mapping of the world through the participation of community involvement around the world.

PhotoSynth is presented by Microsoft as an innovative and original way of publishing and sharing your photos on the Web. It's as easy to use as other photo sharing websites, only that its photo player includes

 special 3D features that makes PhotoSynth especially suitable for panoramas. After logging in with your Windows Live ID and creating a PhotoSynth profile, you're ready to start using the program. Use the client to choose and upload photos, and then check your creation on the web browser (you'll need a special plug-in for this, but this is automatically installed with PhotoSynth). You'll be able to navigate the panorama in a three-dimensional environment by dragging and clicking your mouse around the stitched photos.

                      While Photosynth is definitely an easy yet impressive way to share your pictures online - especially with the full-screen viewer - it lacks all the social tools you find in other similar websites, such as being able to rate pictures or leave comments, just to mention a couple of them.With PhotoSynth you can create, publish and share online your photos in a nicely design interface, with special support for 3D panoramas.

In simple terms, Photosynth allows you to take a bunch of photos of the same scene or object and automatically stitch them all together into one big interactive 3D viewing experience that you can share with anyone on the web.

Photosynth is really two remarkable technical achievements in one product: a viewer for downloading and navigating complex visual spaces and a "synther" for creating them in the first place. Together they make something that seems impossible quite possible: reconstructing the 3D world from flat photographs.

Using techniques from the field of computer vision, Photosynth examines images for similarities to each other and uses that information to estimate the shape of the subject and the vantage point each photo was taken from. With this information, we recreate the space and use it as a canvas to display and navigate through the photos.

Providing that experience requires viewing a lot of data though—much more than you generally get at any one time by surfing someone’s photo album on the web. That’s where  Seadragon™ technology comes in: delivering just the pixels you need, exactly when you need them. It allows you to browse through dozens of 5, 10, or 100(!) megapixel photos effortlessly, without fiddling with a bunch of thumbnails and waiting around for everything to load.We deliver this immersive viewing experience to users on multiple operating systems by tapping into the power of Silverlight, Microsoft’s rich web application technology.

Most Photosynth use is free; You can make public synths, view them, share them with others, and embed them on your website all for free for up to 20 GB of storage

When referring to a stitched collection of photos, “synth” is an abbreviation is used.

                                                Synthy is how we describe really well matched synths. If you create a synth with 100 photos and 100 photos match together, that would be 100% synthy. The synthy % isn’t a perfect quality measurement on its own though. A 4 photo synth that is 100% synthy doesn’t make the best synth. In geek speak: it’s the probability that one can navigate between two photos selected at random, without replacement.

When Photosynth does its magic and matches all your images to each other, it finds common points between the images. It keeps track of those points and gives them a color relevant to the color in the photos that it matched. The result of all these points is the Point Cloud… a 3D reconstruction of the object or scene using common points found in the photos.

The ideal size for a synth is 20-300 photos. While Photosynth can often match many more photos, a huge number of photos makes it harder to view the synth. If you synth with 600 or more images your computer may crunch for hours and hours, attempting to match every image against every other. The result will often be slow to load and not easy for your viewer to move around in. Bigger is not always better!

Microsoft Research has developed a world class panoramic image stitcher called Microsoft Image Composite Editor (ICE ), The latest version of ICE has a “publish to Photosynth” feature. While uploading, exploring and viewing ICE panoramas throughout Photosynth.

 Making a Panorama

Many photosynths consist of photos shot from a single location. Our friends in Microsoft Research have developed a free, world class panoramic image stitcher called Microsoft Image Composite Editor (ICE for short.) ICE takes a set of overlapping photographs of a scene shot from a single camera location, and creates a single high-resolution image. Photosynth now has support for uploading, exploring and viewing ICE panoramas alongside normal synths.

There are many ways to share photos with your beloved ones, both offline and online, but few of them are as spectacular as PhotoSynth.

PhotoSynth is presented by Microsoft as an innovative and original way of publishing and sharing your photos on the Web. It's as easy to use as other photo sharing websites, only that its photo player includes special 3D features that makes PhotoSynth especially suitable for panoramas.

 Applications

·         Uploaded Photosynth collections are now available for viewing on iPhones using iSynth (3D) or Seadragon Mobile (2D only).

·         On April 30, 2008, Photosynth was featured in the episode Admissions of the television show CSI: New York

·         CNN utilized Photosynth for a user-contributed 3D vision of the inauguration of Barack Obama as the President of the United States.

·         In the Angels & Demons "Path of Illumination Contest," Photosynth is used as well as advertised in the website. 

With PhotoSynth you can create, publish and share online your photos in a nicely design interface, with special support for 3D panoramas. Service is currently provided only foe windows and can be extended to other operating system also.

More applications such as Seadragon-Microsoft’s First i-phone applications can be developed.

        Users have the option to geotag their digital shots on sites such as Flickr and then upload them on the online Photosynth web service. Images uploaded on Photosynth give people the ability to seamlessly view landmarks, public spaces and objects from all sides.

One example of this technology in use is the Deep Earth project in which creators are developing an interactive mapping of the world through the participation of community involvement around the world

References:

[1]  www.photosyth.net

[2]  Photosyth Beginner's guide