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Motion in Computer Vision. E. Scott Larsen October 29, 2001 Comp 256. Motion in Computer Vision. The Primary Assumption The BCCE Space-time Images Examples The Aperture Problem The Correspondence Problem (again!) Optical Flow. The Primary Assumption.
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Motion in Computer Vision E. Scott Larsen October 29, 2001 Comp 256
Motion in Computer Vision • The Primary Assumption • The BCCE • Space-time Images • Examples • The Aperture Problem • The Correspondence Problem (again!) • Optical Flow
The Primary Assumption • Observed brightness of any object is constant over time [2] • Motion and gray value changes correspond to each other [1] (in gray images)
The BCCE BCCE: Brightness Change Constraint Equation
Conclusion From the Examples • The Primary Assumption is not always valid (we already knew that) • But… there are other issues also…
The Aperture Problem From left to right, the line appears to have moved in the direction indicated. But…
The Aperture Problem …We open our eyes a little farther, and find that we were wrong.
The Correspondence Problem The grand-pappy of vision problems attacks again!
Optical Flow • “The optical flow is a vector field subject to the BCCE, and is loosely defined as the apparent motion of the image brightness pattern.”[3] • It originates from fluid dynamics. [1] • It is not the same as the motion field: “projection of 3-D physical motion field by the optics onto the image plane.” [1]
Summary • The primary assumption is that image changes and motion directly correspond to each other • Point–point correspondences are required Motion is currently much more useful than I suggest, and there is much room for original investigation.
References • [1] Jähne B., Digital Image Processing, 1997, Springer-Verlag • [2] Sonka M., V. Hlavac and R. Boyle, Image Processing, Analysis, and Machine Vision, 1999, Brooks/Cole • [3] Trucco E., and A. Verri, Introductory Techniques for 3-D Computer Vision, 1998, Prentice-Hall