Recent work [5, 6] showed that learning-based patch
rectification methods are both faster and more reliable than
affine region methods. Unfortunately, their performance improvements
are founded in a computationally expensive offline
learning stage, which is not possible for applications
such as SLAM. In this paper we propose an approach whose
training stage is fast enough to be performed at run-time
without the loss of accuracy or robustness. To this end,
we developed a very fast method to compute the mean appearances
of the feature points over sets of small variations
that span the range of possible camera viewpoints. Then,
by simply matching incoming feature points against these
mean appearances, we get a coarse estimate of the viewpoint
that is refined afterwards. Because there is no need to
compute descriptors for the input image, the method is very
fast at run-time. We demonstrate our approach on trackingby-
detection for SLAM, real-time object detection and pose
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