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  1. Arno Zinke and Andreas Weber. Light Scattering from Filaments. IEEE Transactions on Visualization and Computer Graphics, 2006. Note: Accepted for publication. Keyword(s): light scattering, hair rendering, hair modelling, cloth rendering, cloth modelling.
    Abstract:
    Photo realistic visualization of a huge number of individual filaments like in the case of hair, fur or knitwear, is a challenging task: Explicit rendering approaches for simulating radiance transfer at a filament get totally impracticable with respect to rendering performance, and it is also not obvious how to derive efficient scattering functions for different levels of (geometric) abstraction or how to deal with very complex scattering mechanisms. We present a novel uniform formalism for light scattering from filaments in terms of radiance, which we call {\bf B}idirectional {\bf F}iber {\bf S}cattering {\bf D}istribution {\bf F}unction (BFSDF). We show that previous specialized approaches, which have been developed in the context of hair rendering, can be seen as instances of the BFSDF. Similar to the role of the BSSRDF for surface scattering functions, the BFSDF can be seen as a general approach for light scattering from filaments which is suitable for deriving approximations in a canonic and systematic way. For the frequent cases of distant light sources and observers we deduce an efficient far field approximation ({\bf B}idirectional {\bf C}urve {\bf S}cattering {\bf D}istribution {\bf F}unction, BCSDF). We show that on the basis of the BFSDF parameters for common rendering techniques can be estimated in a non ad-hoc, but physically based way.
    [bibtex-key = ZinkeWeber2005a]


  2. Gerrit Sobottka, Michael Kusak, and Andreas Weber. Hairstyle Construction from Raw Surface Data. In International Conference on Computer Graphics, Imaging and Visualisation (CGIV'06), pages 365-371, 2006. IEEE Computer Society. Keyword(s): hair modelling.
    Abstract:
    We present a novel approach to the problem of hairstyle construction from raw surface data such as the ones obtained from surface scans. Our approach is based on a shape matching algorithm that fits individual hair fibers into a given volume according to a set of boundary conditions and additional hair density information. Our method employs a mechanical rod model based on the special theory of Cosserat rods. Such models can efficiently be used to simulate the deformation of individual fibers in subsequent manipulation steps.
    [bibtex-key = SobottkaKusakWeber06]


  3. Gerrit Sobottka and Andreas Weber. A Symbolic-Numeric Approach to Tube Modeling in CAD Systems. In Computer Algebra in Scientific Computing (CASC '06), volume 4194 of Lecture Notes in Computer Science, pages 279-283, 2006. Keyword(s): Kirchhoff models, hair modelling, computer algebra.
    Abstract:
    In this note we present a symbolic-numeric method to the problem of tube modeling in CAD systems. Our approach is based on the Kirchhoff kinetic analogy which allows us to find analytic solutions to the static Kirchhoff equations for rods under given boundary conditions.
    [bibtex-key = SobottkaWeber06b]


  4. Gerrit Sobottka and Andreas Weber. Computing Static Electricity on Human Hair. In Proceedings of Theory and Practice of Computer Graphics 2006, pages 21-29, 2006. Keyword(s): hair modelling.
    Abstract:
    We present a framework to study electrical charge phenomena on human hair. We propose a fiber based hair model which bases on the special theory of Cosserat Rods to overcome the well known difficulties one has to deal with when simple particle systems are used. We show how such models can efficiently be employed in conjunction with the fast multipole method to account for Coulomb far-field interactions. Furthermore, we extend our model such that we can account for environmental conditions.
    [bibtex-key = SobottkaWeber06a]


  5. Arno Zinke and Andreas Weber. Efficient Ray Based Global Illumination Using Photon Maps. In The Proceedings of the VMV 2006, 2006. Keyword(s): hair modelling, hair rendering, Global Illumination.
    Abstract:
    We introduce a ray based technique to approximate global illumination for complex scenes. If perfect accuracy is not needed, our approach is a simple but more efficient alternative to prior ray based approaches like ray mapping. Our approach combines the simplicity and efficiency of photon mapping with the bias reduction of ray based techniques. The tradeoff between accuracy and efficiency is controlled by only a single parameter. Moreover our algorithm can be easily integrated into existing photon mapping based frameworks.
    [bibtex-key = ZinkeWeberGI06]


  6. Arno Zinke and Andreas Weber. Global Illumination for Fiber Based Geometries. In The Proceedings of the SIACG 2006, 2006. Keyword(s): hair modelling, hair rendering, Global Illumination.
    Abstract:
    Global illumination plays an important role for the visual appearance of light colored hair. We present a novel approach based on photon mapping which allows an efficient physically based approximation of multiple fiber scattering in hair volumes. Our technique can also be applied to other fiber geometries like fur or woven cloth.
    [bibtex-key = ZinkeWeberFibGI06]


  7. Shu Liu 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. Keyword(s): hair modelling, Kirchhoff models, computer algebra.
    Abstract:
    We study solution methods for boundary value problems associated with the static Kirchhoff rod equations. Using the well known Kirchhoff kinetic analogy between the equations describing the spinning top in a gravity field and spatial rods, the static Kirchhoff rod equations can be fully integrated. We first give an explicit form of a general solution of the static Kirchhoff equations in parametric form that is easy to use. Then by combining the explicit solution with a minimization scheme, we develop a unified method to match the parameters and integration constants needed by the explicit solutions and given boundary conditions. The method presented in the paper can be adapted to a variety of boundary conditions. We detail our method on two commonly used boundary conditions.
    [bibtex-key = LiuShuWeber2005]


  8. Gerrit Sobottka, Ebadollah Varnik, and Andreas Weber. Collision Detection in Densely Packed Fiber Assemblies with Application to Hair Modeling. In Hamid R. Arabnia, editor, CISST'05---The 2005 International Conference on Imaging Science, Systems, and Technology: Computer Graphics, Las Vegas, USA, pages 244-250, June 2005. CSREA Press. Keyword(s): hair modelling, collision detection.
    Abstract:
    In this paper we investigate the application of bounding volume hierarchies in collision detection among densely packed fiber assemblies like hair strands or cable looms. In particular, we glance at collision detection algorithms with sub-quadratic upper bound and their practicability and performance in complex dynamic hair scenes. Unlike common collision detection techniques our approach exploits the topological structure of the underlying filament assembly and allows for fast hierarchy updates in dynamic deformable scenes. Furthermore, we compare hierarchies of the wrapped and the layered type and show the feasibility of fiber based collision detection on full human hair models.
    [bibtex-key = SobottkaVarnikWeber2005a]


  9. 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. Keyword(s): hair modelling, collision detection. [bibtex-key = SobottkaWeber2005b]


  10. A. Zinke, G. Sobottka, and A. Weber. Photo-Realistic Rendering of Blond Hair. In B. Girod, M. Magnor, and H.-P. Seidel, editors, Vision, Modeling, and Visualization (VMV) 2004, Stanford, U.S.A., pages 191-198, November 2004. IOS Press. Keyword(s): hair modelling, hair rendering.
    Abstract:
    We present a method for photo-realistic hair rendering, which is based on light scattering from (human) hair fibers. In contrast to existing approaches our method gives realistic results also for light hair types and for close-ups. These results are obtained by using a ``near-field'' model taking into account different scattering components and indirect illumination. Our near-field model is a generalization of previously published methods that can be seen as far-field models. Nevertheless our more general shading model can be used computationally as efficiently as the previous ones.
    [bibtex-key = ZinkeSobottkaWeber2004]


  11. Arnulph Fuhrmann, Gerrit Sobottka, and Clemens Gross. Distance Fields for Rapid Collision Detection in Physically Based Modeling. In Proceedings of GraphiCon 2003, pages 58-65, 2003. Keyword(s): collision detection. [bibtex-key = FuhrmannSobottkaGross2003]


  12. Gerrit Sobottka and Andreas Weber. Geometrische und physikalische Eigenschaften von Human-Haar. Computer Graphics Technical Report CG-2003-1, Institut für Informatik II, Universität Bonn, 53117 Bonn, Germany, 2003. Keyword(s): hair modelling.
    Abstract:
    Im folgenden wird eine \"Ubersicht \"uber die geometrischen und physikalischen Eigenschaften von Haaren gegeben. Unter geometrischen Eigenschaften werden die axiale und die radiale Struktur, sowie die Haarl\"ange verstanden. Die physikalischen Eigenschaften umfassen die Zug-, Biege- und Torsionssteifigkeit, viskoelastisches Verhalten und Hysterese, sowie den Einfluss von Feuchtigkeit, Temperatur und kosmetischen Behandlungen auf eben diese Gr\"o{\ss}en. Dazu z\"ahlen außerdem die Reibung und die optischen Eigenschaften.
    [bibtex-key = SobottkaWeber2003a]


  13. Gerrit Sobottka and Andreas Weber. Über die optischen Eigenschaften von Human-Haar -- Unter besonderer Berücksichtigung der Anforderungen der Computergraphik. Computer Graphics Technical Reports CG-2002-1, Institut für Informatik II, Universität Bonn, 53117 Bonn, Germany, 2002. Keyword(s): hair modelling.
    Abstract:
    Haare weisen eine elliptische Querschnittsgeometrie auf. Der Grad der Elliptizit\"at variiert, wie auch die Welligkeit, mit der Rasse. Der Verlauf der goniophotometrischen Messkurve zeigt f\"ur Haare bei einem Einfallswinkel von 30$^\circ$ ein Maximum bei etwa 24$^\circ$ und ein weiteres von der Haarfarbe abh\"angiges diffuses Maximum bei 40$^\circ$. Die optischen Eigenschaften k\"onnen durch die Applikation von kosmetischen Substanzen wie Haarsprays oder Shampoos beeinflusst werden.
    [bibtex-key = SobottkaWeber2002a]



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Last modified: Thu Nov 9 20:05:54 2006
Author: weber.


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