Generalized Image Acquisition and Analysis

An evaluation of optical flow algorithms for background oriented schlieren imaging

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.


Maximum Mipmaps for Fast, Accurate, and Scalable Dynamic Height Field Rendering

Art Tevs, Ivo Ihrke, Hans-Peter Seidel
In: Proceedings of I3D 2008.


This paper presents a GPU-based, fast, and accurate dynamic height field rendering technique that scales well to large scale height fields. Current real-time rendering algorithms for dynamic height fields employ approximate ray-height field intersection methods, whereas accurate algorithms require pre-computation in the order of seconds to minutes and are thus not suitable for dynamic height field rendering. We alleviate this problem by using maximum mipmaps, a hierarchical data structure supporting accurate and efficient rendering while simultaneously lowering the pre-computation costs to negligible levels. Furthermore, maximum mipmaps allow for view-dependent level-of-detail rendering. In combination with hierarchical ray-stepping this results in an efficient intersection algorithm for large scale height fields.
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author = {Art Tevs and Ivo Ihrke and Hans-Peter Seidel},
title = {Maximum Mipmaps for Fast, Accurate, and Scalable Dynamic Height Field Rendering},
booktitle = {Symposium on Interactive 3D Graphics and Games (i3D'08)},
year = 2008,
pages = {183--190},
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