Before joining MSRA, I
received my Ph.D degree in computer science from
Zhejiang University in
March, 2007. I also hold a Master's degree in mechanical engineering and
a Bachelor's degree in information engineering, both from Zhejiang University.
My research interests include real-time rendering of soft shadows and
participating media, spherical harmonics for real-time rendering, and
real-time global illumination on GPUs. My
Ph.D thesis (in Chinese, with
English abstract) is about precomputation method in interactive global
illumination. During the past several years, I've been really fortunate
to work with ZHOU Kun,
John Snyder,
HUA Wei,GUO Baining,
BAO Hujun,
WANG Rui(ZJU), Steve Lin,
Peter-Pike Sloan,
LIU Xinguo,
Harry Shum and CHEN Lu
on the interesting graphics projects below. That's really a lot of fun.
In my spare time, I like Chinese
calligraphy, music, and swimming.
Research Publications
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Gradient-based Interpolation
and Sampling for Real-time Rendering of Inhomogeneous, Single-scattering
Media
accurately evaluate source radiance
and its gradient at a relative small number of sample points
in the volume, and use gradient-based interpolation to
approximate the source radiance elsewhere;
sample the
interpolation error in the valid sphere of each sample, and
dynamically splitting those with higher estimated error on a
hierarchical grid structure.
use source radiance splatting
to construct the source radiance volume, followed by a ray march to
yield the radiance to the view.
advantages:
all-frequency lighting effects such
as light shaft, volumetric shadows and inhomogeneous glowing;
editable media property;
good scalability with regard to
volume resolution and number of lights;
precomputation
can be avoided for analytical
medium representations.
limitations:
single-scattering only (though it's
possible to be combined with the technique below to incorporate
multiple-scattering);
as a preprocess, decompose density field
into an analytical low-freq RBF representation and a residual field
which can be compressed by
perfect
spatial hashing;
evaluate source radiance at RBF centers,
taking into account only the RBF representation;
use SHEXP to
accelerate single scattering computation, and
BSGP to
accelerate multiple scattering;
compensate for the residuals in the final
ray marching pass.
advantages:
fast smoke rendering with single/multiple
scattering effects and fine details;
editable smoke property;
moderate preprocessing time,
less than an hour for a 600-frame animation.
scholarly use of
the data is automatically granted without permission. the freely evolving smoke
data used in the paper and video is from the authors of
[Shi and Yu 2005], so
it is not shared here. the format of the binary data: volume
resolution(4 bytes) + number of frames(4 bytes) + sequence of density
volumes. note that for some reason the data is split into files of 2GB
or smaller and there's no
headers for the files other than the first one.
accumulate tabulated sphere SH
visibilities, in log space;
approximate SH exponentiation by an
optimal linear model + DC isolation & scaling/squaring techniques;
use sphere hierarchy + receiver clustering
to accelerate run-time computation.
advantages:
fast rendering of soft shadows of
skin-animated characters;
very small precomputation cost: the
tabulation of the log
visibility of a unit sphere is reused for all sphere blockers, and
the sphere approximation for a rest pose of a character is
skin-animated with the geometry.
limitations:
low-frequency lighting, very soft shadows;
can't support generic local lighting.
per-vertex shading, shadow quality
and performance depend on model triangulation. (an extension to
per-pixel shading by Peter-Pike
Sloan et al. is
available)
the visibility
sample is an ASCII file in the following format: version + starting
solid angle (in degrees) + end solid angle (in degrees) + number of samples + visibility and log
visibility zonal harmonic coefficients of each sample, order goes before
the coefficients.
also note that the
physical meaning of the term "log
visibility" has been made clear in our
smoke paper, and that is the negative optical depth. for opaque surfaces, the
optical depth is infinite if the visibility is 0, and 0 if the
visibility is 1.
Intersection Fields for Interactive Global
Illumination
(in Chinese, with English. click to toggle details)
Complex environment lighting has been
increasingly used in interactive graphics applications, such as games,
to provide higher realism compared to conventional artificial light
sources. This paper surveys the real-time rendering
algorithms for dynamic scenes under complex environment lighting, and
tries to characterize these algorithms by reviewing
their base techniques, assumptions, limitations and range of
utilization. Especially, we try to point out the main course
of future research in this domain by analyzing the underlying
relationships between the different algorithms.
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work for personal or classroom use is granted without fee
provided that copies are not made or distributed for profit or
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