Acquisition and Visualization of Optical Material Properties


The optical reflectance behavior of materials and surfaces is of great importance for the perception of a scene. For example, the specific gloss and the texture of a surface give important hints about properties of the material it is made of. Parametric modeling of this behavior is often difficult or even practically impossible. This is especcially true for spatially varying materials. Therefore, in our group we research techniques for the effective data-driven representation of material appearance based on measurements.

In this context we focused on the acquisition, compression, editing and rendering of Bidirectional Texture Functions (BTF). BTFs are six-dimensional functions dependent on surface location as well as incoming and outgoing light directions. It is able to capture the appearance of very complex materials with strong interreflections and shadowing effects. Currently, we are investigating the extension of our RGB BTF techniques to fully spectral BTFs for correct color reproduction under arbitrary illumination.

Several devices for the acquisition of BTF have been built by our group, an overview of these and of our most important publications in this context can be found on this project page.

Ongoing Projects

The image-based acquisition of complex optical material properties is one of the major research topics in our group. The goal of this project is the development of novel techniques for the efficient and high-fidelity capture of high-dimensional material representations like, e.g., the bidirectional texture function (BTF). Example data is publicly available at the BTF database Bonn.
In this project we strive to derive a statistical model of the space spanned by a database of measured BTFs. This way, we intend to develop a dramatically more general representation of materials than is currently available. The goal is to reparameterize the high-dimensional material space to allow perceptually meaningful interpolations between the acquired samples, i.e., to generate new materials that blend qualities of samples from the dataset.
In this project we take image-based reflectance measurements, which are subsequently processed into high quality spatially varying BRDFs (SVBRDFs). We develop alternative approaches to the SVBRDF fitting problem with the help of deep learning.

Completed Projects

The european union funded project 3D-COFORM (3D-COllection-FORMation) deals with the development of novel techniques for digitising objects from the cultural heritage area. The goal is to digitise such objects more efficiently and with better quality compared to the current state-of-the-art. This way 3D-documentation will become an everyday practical choice for digital documentation campaigns in the cultural heritage sector.
In this project we work on the analysis, synthesis and resynthesis of optical material properties of cloth. By estimating domain specific parameters like the weaving pattern and yarn reflection properties from images we obtain a cloth model which can both be visually resynthesized and intuitively edited. We develop new techniques in the context of physically based rendering and image analysis of cloth.
Car paint and especially metallic or pearlescent paints pose serious challenges to computer graphics. This is due to their high dynamic range, their high frequent changes of reflectance both in angular and in spatial domain as well as the angular dependent color shift behaviour of pearlescent paints which is not covered by commonplace reflectance models. In the Car Paint Project we develop new compression, rendering and editing techniques for all kinds of car paints.
The RealReflect project’s goal is to increase the realism of Virtual Reality (VR) technology by developing physically correct visualization technology capable of accounting for phenomena like metamerism, fluorescence and light polarization and integrating it into an existing VR system. This will enable users from many different areas like automotive industry or architecture to create VR simulations for the interior design, thereby avoiding the necessity to build expensive real prototypes which reduces costs as well as time to market of the overall end products.
To correctly simulate materials under arbitrary illumination, the light simulation in a virtual scene must be calculated on a pure spectral basis. This is already done in modern rendering systems. For a few classes of materials spectral reflectance data is already acquired for a few light and view directions using spectrometers and gonioreflectometer setups. This is sometimes enough to fit analytical models to the measured data. But for anisotropic materials or for materials with strong variations in angular or spatial domain there are currently no measurement setups at hand. Similar setups like the ones based on RGB CCD cameras are impractical for spectral measurements because of the high costs of cameras and light sources needed for spectral measurements. In this project we plan to combine RGB and spectral measurement methods to come up with an efficient and pratical measurement setup for spectral BTFs. Furthermore, algorithm for analysis, compression and efficient rendering for such RGB-spectral-combined data will be investigated.
The goal of the project is the creation of the technological bases for a synergetic connection of the innovative service of clothing for the individual customer (tailor-made suit) with the potential of the E-Commerce business using Virtual-Reality (VR) methods.

Selected Publications

In: IEEE Transactions on Visualization and Computer Graphics (2014), PP:99
Michael Weinmann, Juergen Gall, and Reinhard Klein
In proceedings of Computer Vision - ECCV 2014 - 13th European Conference, Zurich, Switzerland, September 6-12, 2014, Proceedings, Part III, pages 156-171, Springer International Publishing, 2014
In proceedings of Computer Vision - ECCV 2014 Workshops, Zurich, Switzerland, pages 321-333, Springer International Publishing, Sept. 2014
In: Computer Graphics Forum (presented at EGSR 2013) (2013), 32(61-71)
B. Levy, X. Tong, and K. Yin (Editors)
In: Computer Graphics Forum (Proc. of Pacific Graphics) (Oct. 2013), 32:7(345-354)
R. Scopigno (Editors)
In: Journal on Computing and Cultural Heritage (JOCCH) (July 2013), 6:3(11:1-11:21)
Holly Rushmeier and Reinhard Klein (Editors)
In proceedings of Eurographics Workshop on Material Appearance Modeling: Issues and Acquisition, Zaragoza, Spain, pages 25-31, Eurographics Association, June 2013
In: Computer Graphics Forum (Proceedings of the Eurographics 2013) (May 2013), 32:2(361-370)
In proceedings of EVA 2012 Berlin, pages 50-57, Gesellschaft zur Förderung angewandter Informatik e.V., Nov. 2012
Kai Schröder, Shuang Zhao, and Arno Zinke
ACM SIGGRAPH Asia 2012: Course Notes, Nov. 2012
In: Computer Graphics Forum (Proc. of Eurographics) (May 2012), 31:2(315-324)
In proceedings of SIGGRAPH Asia 2011 Sketches, Hong Kong, China, pages 28:1-28:2, ACM, Dec. 2011
In proceedings of ACM SIGGRAPH ASIA 2011: Sketches, Hong Kong, China, Dec. 2011
In proceedings of The 12th International Symposium on Virtual Reality, Archeology and Cultural Heritage VAST 2011, Eurographics Association, Prato, Italy, pages 25-32, Eurographics Association, Oct. 2011
In proceedings of The 12th International Symposium on Virtual Reality, Archeology and Cultural Heritage VAST 2011, Eurographics Association, Prato, Italy, pages 113-120, Eurographics Association, Oct. 2011
University of Bonn, Technical Report number CG-2010-1, Dec. 2010
In proceedings of CGIV 2010, Society for Imaging Science and Technology, Joensuu, Finland, pages 326-330, June 2010
Jason Lawrence and Marc Stamminger (Editors)
In: Computer Graphics Forum (Proc. of EGSR) (June 2010), 29:4(1421-1429)
In: Computer Graphics Forum (Proc. of EGSR) (July 2009), 28:4(1181-1188)
In: Computer Graphics Forum (Proc. of Eurographics) (Apr. 2009), 28:2(513-522)
In proceedings of Eurographics Symposium on Parallel Graphics and Visualization, pages 25-32, Mar. 2009
R. Scopigno and E. Gröller (Editors)
In: Computer Graphics Forum (Apr. 2008), 27:2(527-536)
J. Kautz and S. Pattanaik (Editors)
In proceedings of Eurographics Symposium on Rendering 2007, The Eurographics Association, June 2007
Jan Meseth, Gero Müller, Reinhard Klein, Florian Röder, and M. Arnold
In proceedings of The 3rd Symposium on Applied Perception in Graphics and Visualization, July 2006
In proceedings of The 6th International Symposium on Virtual Reality, Archaeology and Cultural Heritage (VAST), Eurographics Association, pages 13-20, Eurographics Association, Nov. 2005
In: Computer Graphics Forum (Mar. 2005), 24:1(83-109)
In proceedings of Computer Graphics International 2004 (CGI 2004), pages 198-205, IEEE Computer Society, June 2004
T. Ertl, B. Girod, G. Greiner, H. Niemann, H.-P. Seidel, E. Steinbach, and R. Westermann (Editors)
In proceedings of Vision, Modeling and Visualisation 2003, pages 271-280, Akademische Verlagsgesellschaft Aka GmbH, Berlin, Nov. 2003
In proceedings of Eurographics Symposium on Rendering 2003, June 2003