Generalized Image Acquisition and Analysis

A Kaleidoscopic Approach to Surround Geometry and Reflectance Acquisition

We describe a system for acquiring reflectance fields of objects without moving parts and without a massively parallel hardware setup. Our system consists of a set of planar mirrors which serve to multiply a single camera and a single projector into a multitude of virtual counterparts. Using this arrangement, we can acquire reflectance fields with an average angular sampling rate of about 120+ view/light pairs per surface point. The mirror system allows for freely programmable illumination with full directional coverage. We employ this setup to realize a 3D acquisition system that employs structured illumination to capture the unknown object geometry, in addition to dense reflectance sampling. On the software side, we combine state-of-the-art 3D reconstruction algorithms with a reflectance sharing technique based on non-negative matrix factorization in order to reconstruct a joint model of geometry and reflectance. We demonstrate for a number of test scenes that the kaleidoscopic approach can acquire complex reflectance properties faithfully. The main limitation is that the multiplexing approach limits the attainable spatial resolution, trading it off for improved directional coverage.

Projects

Time-resolved 3D Capture of Non-stationary Gas Flows

Bradley Atcheson, Ivo Ihrke, Wolfgang Heidrich, Art Tevs, Derek Bradley, Marcus Magnor, Hans-Peter Seidel
In: Proceedings of SIGGRAPH Asia 2008.



Abstract

Fluid simulation is one of the most active research areas in computer graphics. However, it remains difficult to obtain measurements of real fluid flows for validation of the simulated data. In this paper, we take a step in the direction of capturing flow data for such purposes. Specifically, we present the first time-resolved Schlieren tomography system for capturing full 3D, non-stationary gas flows on a dense volumetric grid. Schlieren tomography uses 2D ray deflection measurements to reconstruct a time-varying grid of 3D refractive index values, which directly correspond to physical properties of the flow. We derive a new solution for this reconstruction problem that lends itself to efficient algorithms to robustly work with relatively small numbers of cameras. Our physical system is easy to set up, and consists of an array of relatively low cost rolling-shutter camcorders that are synchronized with a new approach. We demonstrate our method with real measurements, and analyze precision with synthetic data for which ground truth information is available.
Project Page Video

Bibtex

@ARTICLE{Atcheson:2008,
author = {Bradley Atcheson and Ivo Ihrke and Wolfgang Heidrich and Art Tevs and Derek Bradley and Marcus Magnor and Hans-Peter Seidel},
title = {Time-resolved 3D Capture of Non-stationary Gas Flows},
journal = {ACM Transactions on Graphics (Proc. SIGGRAPH Asia)},
year = {2008},
volume = {27},
number = {5},
pages = {132},
}
Go to project list




Imprint-Dataprotection