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Hair Modeling at University of Bonn

On these pages we provide information on hair modeling research of the Computer Graphics Group at University of Bonn.
The primary objective of the hair research at University of Bonn is the development of a high accuracy model for human hair simulation. This includes hair style modeling and physical based hair dynamics simulation as well as hair rendering. Our work is partially supported by Deutsche Forschungsgemeinschaft (DFG).
If you want to contact us please refer to the contact information at the right margin.


Hair Rendering

Rendering hair is very challenging. Thousands or even millions of very thin strands have to be simulated. Surprisingly the complexity also depends on the hair color. For light colored hair multiple fiber scattering (global illumination) plays an important role for the right perception of the hair color and must not be neglected. Based on a general and physically accurate model for light scattering from filaments (Bidirectional Fiber Scattering Distribution Function - BFSDF) we developed techniques for photo-realistic rendering of hair and other fiber based geometry. Using Efficient approximations we are able to simulate all effects of local and global illumination. In contrast to all existing approaches our model gives realistic results also for close-ups, by taking into account 'near-field' scattering. Moreover light colored (blond) hair can be rendered correctly.


light probes from http://www.oliver-mann.de and http://gl.ict.usc.edu/Data/HighResProbes
(Click on thumbs to enlarge.)

(Click on thumbs to enlarge.)



Real Time Rendering of Complex Hairstyles

When rendering light colored hair, multiple fiber scattering is essential for the right perception of the overall hair color. In this context we present a novel technique to efficiently approximate multiple fiber scattering for a full head of human hair or a similar fiber based geometry. In contrast to previous ad-hoc approaches our method relies on the physically accurate concept of the Bidirectional Scattering Distribution Functions and gives physically plausible results. We show that the complex scattering effects can be approximated very well by using aggressive simplifications based on this theoretical model. When compared to unbiased Monte-Carlo path tracing, our approximations still preserve photo-realism in most settings but with rendering times at least two-orders of magnitude lower. Time and space complexity are much lower compared to photon mapping-based techniques and we can even achieve realistic results in real-time on a standard PC with consumer graphics hardware.

Our approach Dual Scattering Approximation for Fast Multiple Scattering in Hair was presented at SIGGRAPH 2008 (click here). A sample animation (selected for SIGGRAPH 2008 Animation Festival) as well as additional images using the novel technique are available from GfaR and Cem Yuksel's homepage.





Collision Detection

We are developing efficient methods for interference detection in densely packed fiber assemblies like hair strands or cable looms with time varying conformation. The main drawbacks of existing approaches are inefficient update schemes as well as bad worst-case time complexity which may occur when fibers are densely packed.


(Click on thumbs to enlarge.)


Publications

Gerrit Sobottka and Andreas Weber. Uebersicht ueber die optischen Eigenschaften von Human-Haar. Technical Report, CG2002/1, Computer Graphics Technical Report Series, Institut fuer Informatik II, Universitaet Bonn, 2002.
Gerrit Sobottka and Andreas Weber. Geometrische und Physikalische Eigenschaften von Human-Haar. Technical Report, CG2003/1, Computer Graphics Technical Report Series, Institut fuer Informatik II, Universitaet Bonn, 2003.
Arnulph Fuhrmann and Gerrit Sobottka and Clemens Gross Distance Fields for Rapid Collision Detection in Physically Based Modeling. Proceedings of GraphiCon 2003, Moscow, Russia, 2003.
A. Zinke and G. Sobottka and A. Weber. Photo-Realistic Rendering of Blond Hair. Proceedings of the VMV, Stanford, 2004.
G. Sobottka and E. Varnik and A. Weber. Collision Detection in Densely Packed Fiber Assemblies with Application to Hair Modeling. Proceedings of the International Conference on Imaging Science, Systems and Technology, CISST '05, Las Vegas, Nevada, 2005.
Liu, Shu and Andreas Weber. A symbolic-numeric method for solving boundary value problems of Kirchhoff rods. In Victor G. Ganzha, Ernst W. Mayr, and Evgenii V. Vorozhtsov, editors, Computer Algebra in Scientific Computing (CASC'05), volume 3718 of Lecture Notes in Computer Science, Kalamata, Greece, pages 387-398, September 2005. Springer-Verlag.
Gerrit Sobottka and Andreas Weber. Efficient Bounding Volume Hierarchies for Hair Simulation. In Second Workshop in Virtual Reality Interactions and Physical Simulations (VRIPHYS '05), Pisa, Italy, November 2005.
Gerrit Sobottka and Michael Kusak and Andreas Weber. Hairstyle Construction from Raw Surface Data. Proceedings of the International Conference on Computer Graphics, Imaging and Visualisation, Sydney, Australia, July 2006, pages 365-371.
Gerrit Sobottka and and Andreas Weber. Computing Static Electricity on Human Hair. Proceedings of Theory and Practice of Computer Graphics 2006 (TPCG'06), Middlesbrough, UK, June 2006, pages 21-29.
Arno Zinke and Andreas Weber. Global Illumination for Fiber Based Geometries. Ibero-American Symposium on Computer Graphics - SIACG (2006), Santiago de Compostela, Spain, July 2006.
Arno Zinke and Andreas Weber. Light Scattering from Filaments - Preprint. To appear in IEEE Transactions on Visualization and Computer Graphics - TVCG 2007.
Arno Zinke and Andreas Weber. Efficient Ray Based Global Illumination Using Photon Maps Proceedings of the VMV, Aachen, 2006.
Gerrit Sobottka and Andreas Weber. A Symbolic-Numeric Approach to Tube Modeling in CAD-Systems. In Victor G. Ganzha, Ernst W. Mayr, and Evgenii V. Vorozhtsov, editors, Computer Algebra in Scientific Computing (CASC'06), volume 4194 of Lecture Notes in Computer Science, Chisinau, Moldova, pages 279-283, September 2006. Springer-Verlag.
Gerrit Sobottka and Tomas Lay and Andreas Weber. Stable Integration of the Dynamic Cosserat Equations with Application to Hair Modeling. Proceedings of WSCG 2008, Plzen, Czech Republic, February 2008.
Arno Zinke, Cem Yuksel, Andreas Weber and John Keyser. Dual Scattering Approximation for Fast Multiple Scattering in Hair. Proceedings of SIGGRAPH 2008 (TOG), 27(3), 2008
Click for selected publications with abstracts ...









If you want to contact the research group at University of Bonn please send an e-mail to one of the following addresses:

Prof. Andreas Weber
mail to: weber()cs.uni-bonn;de

Gerrit Sobottka
mail to: sobottka()cs.uni-bonn;de

Dr. Arno Zinke
mail to: zinke()cs.uni-bonn;de

Tomas Lay Herrera
mail to: tomas()cs.uni-bonn;de















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