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tutorial 6
T6  Capturing Reflectance - From Theory to Practice

Date: Monday, September 3rd, Time: 14:00 - 17:30, Location: Lecture Room 309

Organizers:  Hendrik P. A. Lensch (MPI Informatik)
Michael Goesele (University of Washington)
Gero Müller (Bonn University)
 
Speakers:  Hendrik P. A. Lensch (MPI Informatik)
Michael Goesele (University of Washington)
Gero Müller (Bonn University)


Abstract:

One important problem in photorealistic or predictive rendering nowadays is to realistically model the light interaction with objects. Measurements can capture the reflection properties of real world surface, i.e., they are one way of obtaining realistic reflection properties.

For arbitrary (non-fluorescent, non-phosphorescent) materials, the reflection properties can be described by the 8D reflectance field of the surface, also called BSSRDF. Since densely sampling an 8D function is currently not practical various acquisition methods have been proposed which reduce the number of dimensions by restricting the viewing or relighting capabilities of the captured data sets. In this tutorial we will mainly focus on three different approaches, the first allowing to reconstruct opaque surfaces from a very small set of input images, the second allows for arbitrary surfaces but under the assumption of distant light sources and the last which allows for relighting an arbitrary scene with arbitrary spatially varying light patterns.

After a short introduction explaining some fundamental concepts regarding measuring and representing reflection properties, the basics of data acquisition with photographs will be addressed. The tutorial present the set of current state-of-the art algorithms for acquiring and modeling 3D objects. The tutorial investigates the strengths and limitations of each technique and sorts them by their complexity with regard to acquisition costs. Besides describing the theoretical contributions we will furthermore point out the practical issues when acquiring reflectance fields in order to help interested users to build and implement their own acquisition setup.

The tutorial will be self contained with regard to the principles and concepts used for each acquisition technique. However, attendees should have a working knowledge of basic concepts of realistic rendering and object representations such as triangle meshes or texture maps.


   

   


Syllabus

  1. Introduction (15 min)

    Speaker: Hendrik P. A. Lensch

    • material properties
    • classification of techniques

  2. Acquisition Basics (30 min)

    Speaker: Michael Goesele

    • light sources
    • cameras
    • HDR

  3. Reflectance Sharing (30 min)

    Speaker: Michael Goesele

    • image-based BRDF measurement
    • spatially varying BRDFs

  4. Break (15 min)

  5. Reflectance Fields for Distant Lights (40 min)

    Speaker: Gero Müller

    • BTFs
    • light stage
    • acquisition, compression, synthesis and rendering

  6. Near-field Reflectance Fields (35 min)

    Speaker: Hendrik P. A. Lensch

    • relighting with 4D reflectance fields
    • dual photograph

  7. Conclusion, Questions and Answers


Speakers' Background

Hendrik P. A. Lensch is the head of an independent research group "General Appearance Acquisition and Computational Photography" at the MPI Informatik in Saarbrücken, Germany. The group is part of the Max Planck Center for Visual Computing and Communication. He received his diploma in computers science from the University of Erlangen in 1999 and after joining the computer graphics group at MPI received his PhD from Saarland University in 2003. Dr. Lensch spent two years (2005-2006) as a visiting assistant professor at Stanford University, USA. His research interests include 3D appearance acquisition, image-based rendering and computational photography. For his work on reflectance measurement he received the Eurographics Young Researcher Award 2005. He was awarded an Emmy Noether Fellowship by the German Research Foundation in 2007. He has given several lectures and tutorials at various conferences including SIGGRAPH courses on realistic materials in 2002 and 2005.

Michael Goesele is a postdoctoral research associate in the computer graphics and vision group at the University of Washington. In 1999, he joined the computer graphics group at the MPI Informatik and received his PhD from Saarland University in 2004. His research is focused on a broad range of acquisition techniques for computer graphics including geometry and reflectance capture. Among others, he published two papers at ACM SIGGRAPH about the acquisition of light sources (Accurate Light Source Acquisition and Presentation) and translucent objects (DISCO - Acquisition of Translucent Objects). He has given several lectures and tutorials (e.g. at Eurographics 2002 and SIGGRAPH 2005) about the topics covered in the tutorial.

Gero Müller currently works as a research assistant and Ph.D. student in the computer graphics group of Prof. Reinhard Klein at the University of Bonn, Germany. He received his diploma in computer science from the University of Bonn in 2002. His main research interests are realistic material representations, in particular BTFs. He has authored and co-authored several papers about this topic. At Eurographics 2004 he presented a state-of-the-art report covering the acquisition, compression, synthesis and rendering of BTFs and gave tutorials about the topic at various events (e.g. at Siggraph 2005).



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