Probabilistic models of object shapes

Ali Eslami

University of Edinburgh
Friday, December 14, 2012 at 3:00pm
560 Evans Hall

We address the question of how to build a ‘strong’ probabilistic model of object shapes (binary silhouettes). We define a strong model as one which meets two requirements: 1. Realism – samples from the model look realistic, and 2. Generalization – the model can generate samples that differ from training examples. We consider a class of models known as Deep Boltzmann Machines and show how a strong model of shape can be constructed using a specific form of DBM which we call the ‘Shape Boltzmann Machine’ (ShapeBM). We also present a generative framework for modelling images of objects using an extension of the ShapeBM. Our model employs a factored representation to reason about appearance and shape variability across datasets of images. Parts-based segmentations of objects are obtained simply by performing probabilistic inference in the proposed model. We apply the model to two challenging datasets which exhibit significant shape and appearance variability, and find that it obtains results that are comparable to the state-of-the-art. Joint work with Chris Williams, Nicolas Heess and John Winn. URL: