Edited by author 11-07-2002 01:17 PM
In reply to Sameer: the paper says the sum in Equation (2) is "over all corresponding pairs of pixels i which are inside both images." Of course, there is no mention of how to determine if a pixel is in both images. Perhaps it can be approximated using their hierarchical matching technique if between-frame motion is large enough that a significant number of pixels are not in both images. This is the same idea Serge presented in his Direct Methods vs Feature-Based Methods presentation (Equation (4) of "All About Direct Methods"). It is valid if you assume the brightness constancy constraint.