Partners and International Organizations
(English)
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Duran DUR (F), Albert-Ludwigs Universität Freiburg UFR (D), Ecole Polytechnique Fédérale de Lausanne EPFL (CH), Eyetronics EYE (B), Imagination In Motion IIM (B), Eidgenössische Technische Hochschule Zürich ETH (CH)
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Abstract
(English)
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The most of the effort for this year in the project was devoted toward research and development of hair animation. In this period, a new hair animation methodology and implementation was developed towards MESH IST-1999-10443 deliverable 4.1.2. Continuing from the approach taken for the hair styling in the previous year, we draw on the similarities between hair and fluid flow. However, the focus in this task is hair animation rather than static hair shape.
There are two main difficulties in animating hair for computer graphics.
· An accurate and viable individual stiffness model
· Hair-body, hair-hair and hair-air interactions
We have developed a detailed model for stiffness dynamics of individual hair and we take a novel approach to model the hair-hair interaction via treating hair as continuum. Once we think of hair as continuum, there are two possibilities. Hair can be solid or liquid. Remarkably, hair exhibits a dual behavior. In longitudinal direction, hair acts as a solid. It has a shape memory in terms of bending stiffness and elongation stiffness. However, in the lateral direction it behaves more like a liquid. If one applies shearing stresses, it will continue to deform, the peculiar property of fluids. We discuss how this duality is handled in the subsequent sections.
The implementation is done as a plug-in to Maya to have seamless integration with other animation capabilities of one of the leading industry animation software. The input to the animation plug-in is the static hairstyles defined by the plug-in developed in task 4.1.1. We would like to highlight that though both the methodology use fluid flow as a central theme, there is total difference in the details. We use streamlines as an instrument to model static hair shape. For the dynamics, there is no notion of streamlines.
Currently, the tool is undergoing extensive end in-house user testing and we continue to improve the plug-in in terms of usability, which is the focus of next 6 months of the project.
We address the difficult problem of hair dynamics, particularly hair-hair and hair-air interactions. They have been one of the unsolved problems in computer generated character animation. To model these interactions, we propose to consider hair volume as a continuum. Subsequently, we treat the interaction dynamics to be fluid dynamics. This proves to be a strong as well as viable approach for an otherwise very complex phenomenon. However, we retain the individual character of hair, which is vital to visually realistic rendering of hair animation. For that, we develop an elaborate model for stiffness and inertial dynamics of individual hair strand. Being a reduced coordinate formulation, the stiffness dynamics is numerically stable and fast. We then unify the continuum interaction dynamics and the individual hair's stiffness dynamics.
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