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Institute for
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Julian Martin Fernandez
Psychophysics of SFM for general rotations
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SFM has
been studied almost exclusively in the condition where the axis of rotation
lies in the frontoparallel plane. The ability of humans to recover SFM in the
general case, where the axis of rotation may be tilted out of the
frontoparallel plane, is still poorly understood. Our findings show that
structure recovered from rotations around an axis in the frontoparallel plane
differs from the more general case of structure recovered from rotations
around an arbitrary axis. The former preserves affine structure (i.e., the
correct relief), while the later, in general, does not. This results from the
human’s inability to extract rotational speeds from the instantaneous
velocity field. A possible reason behind this inability could be reducing the
computational complexity of structure from motion computation. The reduction
in complexity comes at the cost of severe distortions in the recovered shape,
including depth-order violations between object parts (Fernandez & Farell,
2005d, coming soon). |