Generalized Image Acquisition and Analysis

Eikonal Rendering: Efficient Light Transport in Refractive Objects

We present a new method for real-time rendering of sophisticated lighting effects in and around refractive objects. It enables us to realistically display refractive objects with complex material properties, such as arbitrarily varying refraction index, inhomogeneous attenuation, as well as spatially-varying anisotropic scattering and reflectance properties. User-controlled changes of lighting positions only require a few seconds of update time. Our method is based on a set of ordinary differential equations derived from the eikonal equation, the main postulate of geometric optics. This set of equations allows for fast casting of bent light rays with the complexity of a particle tracer. Based on this concept, we also propose an efficient light propagation technique using adaptive wavefront tracing. Efficient GPU implementations for our algorithmic concepts enable us to render visual effects that were previously not reproducible in this combination in real-time.


An evaluation of optical flow algorithms for background oriented schlieren imaging

Bradley Atcheson, Wolfgang Heidrich, Ivo Ihrke
In: Experiments in Fluids 2009.


The background oriented schlieren method (BOS) allows for accurate flow measurements with a simple experimental configuration. To estimate per-pixel displacement vectors between two images, BOS systems traditionally borrow window-based algorithms from particle image velocimetry. In this paper, we evaluate the performance of more recent optical flow methods in BOS settings. We also analyze the impact of different background patterns, suggesting the use of a pattern with detail at many scales. Experiments with both synthetic and real datasets show that the performance of BOS systems can be significantly improved through a combination of optical flow algorithms and multiscale background.
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author = {Bradley Atcheson and Wolfgang Heidrich and Ivo Ihrke},
title = {An evaluation of optical flow algorithms for background oriented schlieren imaging},
journal = {Experiments in Fluids},
year = {2008},
volume = {to appear},
number = {},
pages = {},
doi = {10.1007/s00348-008-0572-7}
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