Electrical Engineering and Computer Science

AI Seminar

Dual Photography

Pradeep Sen

Thursday, October 27, 2005
4:00pm - 5:00pm
1005 EECS

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About the Event

In this talk, I will present a novel photographic technique called dual photography, which exploits Helmholtz reciprocity to interchange the lights and cameras in a scene. With a video projector providing structured illumination, reciprocity permits us to generate pictures from the viewpoint of the projector, even though no camera was present at that location. The technique is completely image-based, requiring no knowledge of scene geometry or surface properties, and by its nature automatically includes all transport paths, including shadows, inter-reflections and caustics. In its simplest form, the technique can be used to take photographs without a camera. I will show results of images we captured using only a projector and a photo-resistor. If the photo-resistor is replaced by a camera, we can produce a 4D dataset that allows for relighting with 2D incident illumination. Using an array of cameras we can produce a 6D slice of the 8D reflectance field that allows for relighting with arbitrary light fields. Since an array of cameras can operate in parallel without interference, whereas an array of light sources cannot, dual photography is fundamentally a more efficient way to capture such a 6D dataset than a system based on multiple projectors and one camera. As an example, I will describe how dual photography can used to capture and relight scenes.


Pradeep Sen is a PhD candidate in Electrical Engineering in the Graphics Laboratory at Stanford University. He received his BS degree in Computer and Electrical Engineering from Purdue University in 1996 and his M.S. in Electrical Engineering in 1998 in the area of electron-beam lithography. He joined the Graphics Lab in the fall of 2000, and for his doctoral thesis he developed a structure that embeds discontinuity information in a texture in order to reduce rendering artifacts. These "silhouette maps" can be applied to various problems in computer graphics such as texture magnification and shadow mapping. Other publications in graphics include work on real-time shading and dual photography. His interests include real-time graphics and graphics hardware, global illumination algorithms, computational photography and display technology.

Additional Information

Contact: Igor Guskov

Phone: 37244

Email: guskov@umich.edu

Sponsor(s): Prof. Guskov, CSE

Open to: Public

Web Page: http://graphics.stanford.edu/papers/dual_photography/