Defocus Difference Matting


Morgan McGuire Wojciech Matusik
Brown University MERL
Technical Sketch
Siggraph 2005





Matting is a classic problem in both computer graphics and vision. Practical solutions that yield high quality results are important for special effects in the movie industry. In our defocus difference matting (DDM) approach, we assume that the background is known, typically because it is static and prerecorded. In this respect, our work is related to blue-screen matting. Two common problems with blue-screen matting are the limitations imposed on the color of the foreground, e.g., the actor cannot wear a blue shirt, and more importantly a color spill of the background on the foreground, which considerably changes the lighting of the scene. Our method alleviates both of these problems. When the background is known, pulling the matte is still an underconstrained problem. Smith and Blinnís triangulation method used two different backgrounds, which is not practical for live subjects. We instead constrain the solution by using two video streams that share a common center of projection but different focus characteristics.



Morgan McGuire, Wojciech Matusik. Defocus Difference Matting. Technical Sketch, Siggraph 2005.