Generalized Image Acquisition and Analysis

Dynamic Display of BRDFs

This paper deals with the challenge of physically displaying reflectance, i.e., the appearance of a surface and its variation with the observer position and the illuminating environment. This is commonly described by the bidirectional reflectance distribution function (BRDF). We provide a catalogue of criteria for the display of BRDFs, and sketch a few orthogonal approaches to solving the problem in an optically passive way. Our specific implementation is based on a liquid surface, on which we excite waves in order to achieve a varying degree of anisotropic roughness. The resulting probability density function of the surface normal is shown to follow a Gaussian distribution similar to most established BRDF models.

Projects

From Capture to Simulation - Connecting Forward and Inverse Problems in Fluids

James Gregson, Ivo Ihrke, Nils Thuerey, Wolfgang Heidrich
SIGGRAPH 2014



Abstract

We explore the connection between fluid capture, simulation and proximal methods, a class of algorithms commonly used for inverse problems in image processing and computer vision. Our key finding is that the proximal operator constraining fluid velocities to be divergence-free is directly equivalent to the pressure-projection methods commonly used in incompressible flow solvers. This observation lets us treat the inverse problem of fluid tracking as a constrained flow problem all while working in an efficient, modular framework. In addition it lets us tightly couple fluid simulation into flow tracking, providing a global prior that significantly increases tracking accuracy and temporal coherence as compared to previous techniques. We demonstrate how we can use these improved results for a variety of applications, such as re-simulation, detail enhancement, and domain modification. We furthermore give an outlook of the applications beyond fluid tracking that our proximal operator framework could enable by exploring the connection of deblurring and fluid guiding.
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Bibtex

@article{Gregson:14,
author = {James Gregson and Ivo Ihrke and Nils Thuerey and Wolfgang Heidrich},
title = {From Capture to Simulation - Connecting Forward and Inverse Problems in Fluids},
journal = {ACM Trans. on Graphics (SIGGRAPH'14)},
volume = 33, number = 4, year = 2014,
pages = {xx--yy},
}
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