e-mail: my first name@dgp.toronto.edu
work phone: +1 (416) 946-8427
| Home | Publications (brief) | All Abstracts & Files | Academic Service | Completed Internships |
| I am a Ph.D candidate in the Dynamic Graphics Project lab at the University of Toronto. I completed a BASc in Honours Computer Engineering from the University of Waterloo in May 2005 and an MSc in Computer Science from the University of Toronto in October 2006. My research interests are realistic image synthesis, high-performance rendering using commodity graphics hardware and methods for real-time fluid simulation and animation. My supervisor is Dr. Eugene Fiume. I completed an internship at MSR Redmond in 2008 working on interactive illumination effects under the supervision of Dr. John Snyder. I will be conducting research at Disney Research Zurich as an intern during the summer of 2009 with Dr. Wojciech Jarosz. |
e-mail: my first name@dgp.toronto.edu work phone: +1 (416) 946-8427 |
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Solving Radiance Transport as a Differential EquationDerek Nowrouzezahrai and Chris Gonterman AbstractWe introduce an alternative to Monte-Carlo techniques for solving radiance transport problems for participating media. We use a reformulation of the volume rendering equation from its standard integro-differential form to a purely differential form. We then leverage the large body of work in numerical methods for solving differential equations by framing and analyzing the problem as a differential equation. To our knowledge, this is the first application of such techniques in the area of photo-realistic rendering of volumes based on ray optics. CitationDerek Nowrouzezahrai and Chris Gonterman. Solving radiance transport as a differential equation. Technical Report CSRG-588, Department of Computer Science, University of Toronto, Toronto, Canada, December 2008. [BiBTeX] 
Fast Soft Self-Shadowing on Dynamic Height FieldsJohn Snyder and Derek Nowrouzezahrai AbstractWe present a new, real-time method for rendering soft shadows from large light sources or lighting environments on dynamic height fields. The method first computes a horizon map for a set of azimuthal directions. To reduce sampling, we compute a multi-resolution pyramid on the height field. Coarser pyramid levels are indexed as the distance from caster to receiver increases. For every receiver point and every azimuthal direction, a smooth function of blocking angle in terms of log distance is reconstructed from a height difference sample at each pyramid level. This function's maximum approximates the horizon angle. We then sum visibility at each receiver point over wedges determined by successive pairs of horizon angles. Each wedge represents a linear transition in blocking angle over its azimuthal extent. It is precomputed in the order-4 spherical harmonic (SH) basis, for a canonical azimuthal origin and fixed extent, resulting in a 2D table. The SH triple product of 16D vectors representing lighting, total visibility, and diffuse reflectance then yields the soft-shadowed result. Two types of light sources are considered; both are distant and low-frequency. Environmental lights require visibility sampling around the complete 360 degree azimuth, while key lights sample visibility within a partial swath. Restricting the swath concentrates samples where the light comes from (e.g. 3 azimuthal directions vs. 16-32 for a full swath) and obtains sharper shadows. Our GPU implementation handles height fields up to 1024x1024 in real-time. The computation is simple, local, and parallel, with performance independent of geometric content. CitationJohn Snyder and Derek Nowrouzezahrai. Fast soft self-shadowing on dynamic height fields. Computer Graphics Forum: Eurographics Symposium on Rendering, 27(4):1275–1283, June 2008. [BiBTeX] Links
Shadowed Relighting of Dynamic Geometry with 1D BRDFsDerek Nowrouzezahrai, Evangelos Kalogerakis, Patricio Simari, and Eugene Fiume AbstractWe present a method for synthesizing the dynamic self-occlusion of an articulating character in real-time (> 170Hz) while incorporating reflection effects from 1D BRDFs under dynamic lighting and view conditions. We introduce and derive a general operator form for convolving spherical harmonics (SH) occlusion vectors with arbitrary 1D BRDF kernels. This operator, coupled with a compact linear model for predicting SH occlusion over articulating meshes, segments the BRDF and visibility terms of the direct illumination integral. We illustrate our results on a thin-membrane translucency model and the normalized Phong BRDF. CitationDerek Nowrouzezahrai, Evangelos Kalogerakis, Patricio Simari, and Eugene Fiume. Shadowed relighting of dynamic geometry with 1d brdfs. Proceedings of Eurographics Short Papers, January 2008. [BiBTeX] Links
Video browsing by direct manipulationPierre Dragicevic, Gonzalo Ramos, Jacobo Bibliowicz, Derek Nowrouzezahrai, Ravin Balakrishnan, and Karan Singh AbstractWe present a method for browsing videos by directly dragging their content. This method brings the benefits of direct manipulation to an activity typically mediated by widgets. We support this new type of interactivity by: 1) automatically extracting motion data from videos; and 2) a new technique called relative flow dragging that lets users control video playback by moving objects of interest along their visual trajectory. We show that this method can outperform the traditional seeker bar in video browsing tasks that focus on visual content rather than time. CitationPierre Dragicevic, Gonzalo Ramos, Jacobo Bibliowicz, Derek Nowrouzezahrai, Ravin Balakrishnan, and Karan Singh. Video browsing by direct manipulation. In CHI '08: Proceeding of the twenty-sixth annual SIGCHI conference on Human factors in computing systems, pages 237–246, New York, NY, USA, 2008. ACM. [BiBTeX] Links
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