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We conduct an experiment to verify the hypothesis that natural visual objects can be efficiently
represented by few and simple shape motifs (such as
ellipsoids), that compose a deformable
shape script model.
The shape script model is a hierarchical deformable model. Inside the shape script model, shape motifs can locally perturb their locations, orientations, scales and aspect ratios locally relative to the whole object. Shape motifs are represented as deformable active basis models composed of Gabor wavelet elements; Gabor wavelet elements can also perturb their locations and orientations locally relative to the shape motif.
The underlying top down generating process performs in two steps. First, a collection of shape motifs at a few selected positions, orientations, aspect ratios and scales generate a sparse "shape map", denoting a few locations and orientations to place Gabor wavelet elements and their corresponding coeffients (strengths). Second, the shape map generates the image by linearly adding up Gabor wavelet elements.
When matching a shape script template to a newly observed image, we adopt a bottom up recursive SUM/MAX procedure, which is essentially a dynamic programmming strategy.