When done correctly, a digitally recorded facial performance is an accurate measurement of the pe... more When done correctly, a digitally recorded facial performance is an accurate measurement of the performer's motions. As such it reflects all the idiosyncrasies of the performer. However, often the digital character that needs to be animated is not a digital replica of the performer. In this case, the decision to use performance capture might be motivated by cost issues, the
Alpha matting is widely used in video conferencing as well as in movies, television, and social m... more Alpha matting is widely used in video conferencing as well as in movies, television, and social media sites. Deep learning approaches to the matte extraction problem are well suited to video conferencing due to the consistent subject matter (front-facing humans), however training-based approaches are somewhat pointless for entertainment videos where varied subjects (spaceships, monsters, etc.) may appear only a few times in a single movie – if a method of creating ground truth for training exists, just use that method to produce the desired mattes. We introduce a training-free high quality neural matte extraction approach that specifically targets the assumptions of visual effects production. Our approach is based on the deep image prior, which optimizes a deep neural network to fit a single image, thereby providing a deep encoding of the particular image. We make use of the representations in the penultimate layer to interpolate coarse and incomplete "trimap" constraints. Videos processed with this approach are temporally consistent. The algorithm is both very simple and surprisingly effective.
Algorithmic (KCS) complexity results can be interpreted as indicating some limits to software est... more Algorithmic (KCS) complexity results can be interpreted as indicating some limits to software estimation. While these limits are abstract they nevertheless contradict enthusiastic claims occasionally made by commercial software estimation advocates. Specifically, if it is accepted that algorithmic complexity is an appropriate definition of the complexity of a programming project, then claims of purely objective estimation of project complexity, development time, and programmer productivity are necessarily incorrect.
Assumptions of brightness constancy and spatial smoothness underlie most optical flow estimation ... more Assumptions of brightness constancy and spatial smoothness underlie most optical flow estimation methods. In contrast to standard heuristic formulations, we learn a statistical model of both brightness constancy error and the spatial properties of optical flow using image sequences with associated ground truth flow fields. The result is a complete probabilistic model of optical flow. Specifically, the ground truth enables us to model how the assumption of brightness constancy is violated in naturalistic sequences, resulting in a ...
Phase und brachten pro Pflanze mehr Bliiten und Samen hervor. Der Samenvorrat im Boden war gering... more Phase und brachten pro Pflanze mehr Bliiten und Samen hervor. Der Samenvorrat im Boden war gering, und nach dem Auslegen von Samenproben im Herbst und Fruhjahr zeigte sich, daB die Samen im Boden nicht lange lebensfahig bleiben. In Laborversuchen wurden bei hoheren Windgeschwindigkeiten groBere Ausbreitungsentfernungen erreicht, wobei der Wind die Samen vor allem nach ihrer Landung forttrieb. Widerstande, die einen Pflanzenbestand simulierten, unterbanden diese Fortbewegung nach der Landung fast vollstandig, so daB die Ausbreitung schlieBlich bei alien Windgeschwindigkeiten fast gleich war. Bei Untersuchungen im Freiland mit Samenfallen und anhand von Keimpflanzen bestatigte sich dasselbe Verteilungsmuster der Achanen um ihre Mutterpflanze. Die Bedeutung dieser Ergebnisse fur die Entwicklung von Distelpopulationen werden diskutiert.
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Papers by j.p. lewis