Bath, 25 Years of CG Hair Modelling, Animation, and Rendering Wen Tang School of Computing, University of Teesside

Bath, 25 Years of CG Hair Modelling, Animation, and Rendering Objectives of this presentation A literature review of hair techniques from the past to the present. To showcase the advancement in high visual complexity techniques in computer graphics using hair as an example. A personal view of future development in the area.

Bath, 25 Years of CG Hair Modelling, Animation, and Rendering Human hair is a crucial element for computer generated characters. Early work on computer generated hair is by Kajiva & Kay The latest work is Scheuermanns real-time realistic hair rendering in years later [Kajiya & Kay 1989][Scheuermann 2004]

Bath, 25 Years of CG Hair Modelling Hair modelling involves the task of dealing with high-density hair strands, stylistic strand variations, and the mappings between the volumetric nature of hair to surface models (characters head models). Animal fur and short hair modelling [Kajiya and Kay 1989; Neyret, 1997; Lengyel et al. 2001]. Long hair modelling and styling [Anjyo et al. 1992; Hadap and Thalmann 2001; Lee and Ko 2001].

Bath, 25 Years of CG Hair Modelling Individual hair strand model Wisp models are to generate a cluster of adjacent hair stands that have the same tendency in style and motions. Wisp models utilise modelling parameters such as numbers of stands in a cluster, shapes of wisps, and lengths of wisps for style variations. [Xu & Yang 2001] [Kim & Neumann 2002 ]

Bath, 25 Years of CG Hair Modelling Methods for mapping volumetric hair to the surface of head models A scalp surface method can be obtained by extracting a copy of the head polygons to form a new mesh. Image maps are usually used to indicate the hair colour and the growing direction and position of a hair strand. This systematic approach provides flexibilities to create different hair types.

Bath, 25 Years of CG Hair Modelling Example of hair types (TAnG Group, Teesside) Colour mapOrientation map Colour map position map

Bath, 25 Years of CG Hair Modelling – Example of hair types (TAnG Group, Teesside)

Bath, 25 Years of CG Hair Animation Difficult problems with hair animation Realistic hair-hair, hair-body, and hair-air interactions. Real-time hair dynamics. Existing approaches: Spring-mass model Dynamic continuum model [Hadap and Magnenat- Thalmann 2001] Cluster wisp model [Plante et al 2001] Loosely connected particle model [Bando et al 2003] NURBS surface shell model [Montoya-vozmediano & Hammel 2003; Noble & Tang 2004]

Bath, 25 Years of CG Hair Animation [TAnG Group, Teesside] [Hadap and Magnenat-Thalmann 2001] [Bertails et al 2003] [Bando et al 2003]

Bath, 25 Years of CG Hair Animation [Noble & Tang 2004]

Bath, 25 Years of CG Hair Animation Image from Final Fantasy (Kais hair)

Bath, 25 Years of CG Hair Rendering Hair rendering One important aspect is to simulate the light scattering from fibres. This task also involves simulating the light reflection from the fibre surfaces and the translucent properties of the fibres including volume absorption of light and inter- reflection Kays model [ Kajiya & Kay 1989] Marschners model [ Marschner et al 2003]

Bath, 25 Years of CG Hair Rendering [Marschner et al 2003] [Scheuermann 2004] [Marschner et al 2003] [Kajiya & Kay 1989]

Bath, 25 Years of CG Modelling and Animating Cartoon Hair with NURBS Surfaces [Noble & Tang 2004]

Bath, 25 Years of CG Hair Modelling, Animation, and Rendering Conclusion High standard results are achieved, but there is a lack of successful integrated solutions that would work in all three aspects of hair simulation. Creating good looking hair remains a tedious task. Realistic real-time hair is a highly desirable feature in the CG industry. Traditional art is a rich source of inspiration for artistic hair.

Bath, 25 Years of CG Hair Modelling, Animation, and Rendering References: Anjyo, K., Usami, Y., and Kurihara, T A Simple Method for Extracting the Natural Beauty of Hair. Proceedings of ACM SIGGRAPH92, 26(4), pp Bando, Y., Chen, B. Y., and Nishita, T Animating Hair with Loosely Connected Particles. Proceedings of EUROGRAPHICS 2003, vol 22(2003). No.3. Bertails, F., Kim, Cani, M. P., and Neumann, U Adaptive Wisp-Tree – A Multiresolution Control Structure for Simulating Dynamic Clustering in Hair Motion. Symposium on Computer Animation'03, July Hadap, S. and Thalmann. N. M Modelling Dynamic Hair as a Continuum. Proceedings of EUROGRAPHICS2001. Kajiya, J. and Kay, T Rendering Fur with Three Dimensional Textures. Proceedings of ACM SIGGRAPH89, 23(4), pp Lee, D. W. and Ko, H. S., 2001 Natural Hairstyle Modelling and Animation. Graphical Models, 63(2), Lengyel, J. E., Praun, E., Finkelstein, A., and Hoppe, H Real-time Fur over Arbitrary Surfaces. ACM Symposium on Interactive 3D Techniques 2001, Marschner, R. S., Jensen, H. W., Cammarano, M., Worley, S., and Hanrahan, P Light Scattering from Human Hair Fibers. ACM SIGGRAPH04. Neyret, F Modelling, Animating, and Rendering Complex Scenes Using Volumetric Textures. IEEE Transaction on Visualization and Computer Graphics, 4(1), Plante, E., Cani, M. P., and Poulin, P A Layered Wisp Model for Simulating Interactions Inside Long Hair. Eurographics Workshop on Computer Animation and Simulation 2001, pp Scheuermann. T. Practical Real-time Hair Rendering and Shading. ACM SIGGRAPH04 Sketch Xu, Z. and Yang, X. D H-HairStudio: An Interactive Tool for Hair Design. IEEE Computer Graphics and Applications, 21(3),