Generalized Image Acquisition and Analysis

Discovering the Structure of a Planar Mirror System from Multiple Observations of a Single Point

We investigate the problem of identifying the position of a viewer inside a room of planar mirrors with unknown geometry in conjunction with the room’s shape parameters. We consider the observations to consist of angularly resolved depth measurements of a single scene point that is being observed via many multi-bounce interactions with the specular room geometry. Applications of this problem statement include areas such as calibration, acoustic echo cancelation and time-of-flight imaging. We theoretically analyze the problem and derive sufficient conditions for a combination of convex room geometry, observer, and scene point to be reconstructable. The resulting constructive algorithm is exponential in nature and, therefore, not directly applicable to practical scenarios. To counter the situation, we propose theoretically devised geo- metric constraints that enable an efficient pruning of the solution space and develop a heuristic randomized search algorithm that uses these constraints to obtain an effective solution. We demon- strate the effectiveness of our algorithm on extensive simulations as well as in a challenging real-world calibration scenario.

Projects

Property and Lighting Manipulations for Static Volume Stylization Using a Painting Metaphor

Oliver Klehm, Ivo Ihrke, Hans-Peter Seidel, Elmar Eisemann
TVCG 2014



Abstract

Although volumetric phenomena are important for realistic rendering and can even be a crucial component in the image, the artistic control of the volume’s appearance is challenging. Appropriate tools to edit volume properties are missing, which can make it necessary to use simulation results directly. Alternatively, high-level modifications that are rarely intuitive, e.g., the tweaking of noise function parameters, can be utilized. Our work introduces a solution to stylize single-scattering volumetric effects in static volumes. Hereby, an artistic and intuitive control of emission, scattering and extinction becomes possible, while ensuring a smooth and coherent appearance when changing the viewpoint. Our method is based on tomographic reconstruction, which we link to the volumetric rendering equation. It analyzes a number of target views provided by the artist and adapts the volume properties to match the appearance for the given perspectives. Additionally, we describe how we can optimize for the environmental lighting to match a desired scene appearance, while keeping volume properties constant. Finally, both techniques can be combined. We demonstrate several use cases of our approach and illustrate its effectiveness.
Video

Bibtex

@article{Klehm:14,
author = {Oliver Klehm and Ivo Ihrke and Hans-Peter Seidel and Elmar Eisemann},
title = {Property and Lighting Manipulations for Static Volume Stylization Using a Painting Metaphor},
journal = {Transactions of Visualization and Computer Graphics},
year = 2014,
pages = {xx--yy},
}
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