COMP 768 Project Proposal
Motivation
Simulating
hair is very important for realistic simulation and rendering of
virtual human, however, it remains a challenge especially for
interactive applications. Although rencently animation industry have
been able to produce highly plausible hair with accurate motion and
appearance, these results were mostly obtained offline. The biggest
challenge that has been perventing hair simulation from achieving
real-time is the large number of individual hair strands that need to
be simulated and rendered, the average number of a full head of
hair consists of no less than 100,000 strands.
Various techniques have been proposed
to accelerate hair simulation, either by using simplified geometry, multiresolution geometrical representaiton
and simulation LODs, or by using graphics hardware. However,
over-simplification might lead to hair appearing too chunky or
unnatural, especially for curly hair, and there might be visible
artifacts between transtion of different level of details. These
limitations mean that we are still facing the challenge of real-time
hair simulation, and this motivates this project.
Literature and Background
There have been three different frameworks of multiresolution
representations of hair. One is the wisp model. The authors started
from addressing the static modeling problem and went
further to handle the dynamics by building a separate simulation LOD
callsed adaptive wisp trees. Another proposed multiresolution
approach chose to use three levels, strip,
cluster, and strand, each based on subdivided surfaces and curves. It
incorporates simulation LODs and is able to do continuous transitions
dynamically on the fly. A more recent model used
super-helices to model hair strands and used the derived dynamic
equaitons to handle the dynamics. This is a more physically
accurate model but is also more computationally demanding, therefore
the authors were currently limited to only using ten guided strands to
model a full head of hair.
Poposed Tasks and Goals
A short term goal of this project is to migrate Kelly Ward's hair LOD
model
to GPU. This part overlaps with one of my conceurrent projects that
implements SSVs on GPU, because SSV is the underlying BV used for
Kelly's hair LODs. A long term goal is to incorporate and improve in
the aspect of simulation LODs. In particular, current transition
criteria do not take collision into account, which might be a
major shortcoming. A more remote goal would be to try to apply LOD
technique on the more physically-based model of Kerchhoff equations and
super helices.
Timeline and Checkpoints
By April 7th, I aim to have implemented a basic
geometric LODs using graphics hardware, including collision detection
and simple mass spring system dynamics. By May 5th, I aim to have
implemented more improved dynamics system with simulation LODs.
Project Proposal Slides
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Reference
1. T.-Y.
Kim and U. Neumann, “Interactive
multiresolution hair modeling and editing,” ACM Transactions on
Graphics, vol.
21, no.
3, pp. 620– 629, July 2002, proceedings of ACM SIGGRAPH 2002.
2.
K. Ward and M. C. Lin, “Adaptive grouping
and subdivision for simulating hair dynamics,” in Pacific
Graphics Conference
on
Computer Graphics and Applications, October 2003, pp. 234–243.
3. F.
Bertails, T.-Y. Kim, M.-P. Cani, and U.
Neumann, “Adaptive wisp tree -a multiresolution control structure
for
simulating
dynamic clustering in hair motion,” in ACM SIGGRAPH Symposium on
Computer Animation, July 2003, pp. 207–213.
4. F. Bertails, B. Audoly, M.-P. Cani, B.
Querleux, F. Leroy, and J.-L. L′ev.eque, "Super-helices
for predicting the
dynamics of natural hair," in ACM Transactions on Graphics
(Proceedings of the SIGGRAPH conference), August 2006.
5. K.
Ward, M. C. Lin, J. Lee, S. Fisher, and
D. Macri, “Modeling hair using level-of-detail
representations,” in
International
Conference on Computer Animation and Social Agents, May 2003,
pp.
41–47.
6. K.
Ward, F. Bertails, T.-Y. Kim, S. R. Marschner, M.-P. Cani, M. C. Lin. A
Survey on Hair Modeling: Styling, Simulation
and Rendering. IEEE Transactions on Visualization and Computer Graphics, vol. 13, no. 2,
pp. 213-234, Mar/Apr. 2007.
7.
E. Plante, M.-P. Cani, P. Poulin. "A Layered Wisp Model for Simulating
Interactions inside Long Hair." in Proceedings of
Eurographics Worshop on
Animation and Simulation. 2001.
8.
K. Ward, N. Galoppo, M. Lin. "Interactive Virtual Hair Salon."
Presence. 2007. Vol. 16. No. 3.
9. K. Ward. "Simplified Representatiins for Modeling Hair." UNC-CS Tech report. 2002.
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