“Real-time triangulation matting using passive polarization” by McGuire and Matusik

Blue screen matting separates foreground and background elements of video for special effects shots. It balances the benefit of real-time performance against the drawbacks of blue light spill through-out the scene. In this sketch we replace the traditional blue screen with a gray, polarized one, and film the scene with a single camera containing two differently-polarized sensors. For each frame, this camera simultaneously captures an image of the actor against an apparently black background and an apparently gray background. From these two images we can triangulate the foreground color and matte; this is an extension of a mathematically similar idea by Smith and Blinn that was previously applicable only to static scenes.Our new method operates in real-time on video. It has comparable controls and setup to blue-screen matting, which is the de facto standard for practicality. Unlike blue-screen matting, our gray screen does not impact the illumination color of the scene.

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2. Smith, A. R., and Blinn, J. F. 1996. Blue screen matting. In SIG-GRAPH ’96, ACM Press, 259–268.