Kun Xu

Kun Xu (xukun)

I am a fourth year Ph.D Student of Department of Computer Science and Technology in Tsinghua University, under supervision of Prof. Shi-Min Hu. Before that, I received my bacholor degree from Department of Computer Science and Technology. Tsinghua University in 2005.

My research interests include: real-time rendering, precomputed radiance transfer, appearance modeling.

My contact info:
Email: xu-k (at) mails.tsinghua.edu.cn
Phone: 86-10-62797001-803 (Office)
Address: FIT Building 3-523, Tsinghua Unveristy, Beijing, P.R. China, P.C.: 100084


  Publications

SPCBF

Spherical Piecewise Constant Basis Functions for All-Frequency Precomputed Radiance Transfer
Kun Xu, Yun-Tao Jia, Hongbo Fu, Shi-Min Hu, Chiew-Lan Tai
Accepted by IEEE Transaction of Visualization and Computer Graphics (TVCG).

This paper presents a novel basis function, called spherical piecewise constant basis function (SPCBF), for precomputed radiance transfer. SPCBFs have several desirable properties: rotatability, ability to represent all-frequency signals, and support for efficient multiple product. By partitioning the illumination sphere into a set of subregions, and associating each subregion with an SPCBF valued 1 inside the region and 0 elsewhere, we precompute the light coefficients using the resulting SPCBFs. We run-time approximate BRDF and visibility coefficients with the same set of SPCBFs through fast lookup of summed-area-table (SAT) and visibility distance table (VDT), respectively. SPCBFs enable new effects such as object rotation in all-frequency rendering of dynamic scenes and onthe-fly BRDF editing under rotating environment lighting. With graphics hardware acceleration, our method achieves real-time frame rates.

[ paper ] [ video ]


eg
Real-time homogeneous translucent material editing
Kun Xu, Yue Gao, Yong Li, Tao Ju, Shi-Min Hu
Accepted by EuroGraphics 2007.

This paper presents a novel method for real-time homogeneous translucent material editing under fixed illumination. We consider the complete analytic BSSRDF model proposed by Jensen et al.[JMLH01], including both multiple scattering and single scattering. Our method allows the user to adjust the analytic parameters of BSSRDF and provides high-quality, real-time rendering feedback. Inspired by recently developed Precomputed Radiance Transfer (PRT) techniques, we approximate both the multiple scattering diffuse reflectance function and the single scattering exponential attenuation function in the analytic model using basis functions, so that re-computing the outgoing radiance at each vertex as parameters change reduces to simple dot products. In addition, using a non-uniform piecewise polynomial basis, we are able to achieve smaller approximation error than using bases adopted in previous PRT-based works, such as spherical harmonics and wavelets. Using hardware acceleration, we demonstrate that our system generates images comparable to [JMLH01] at real-time frame-rates.

[ paper ] [ video ]

Spherical Harmonics Scaling
Jiaping Wang, Kun Xu, Kun Zhou, Stephen Lin, Shimin Hu, Baining Guo
Pacific Conference on Computer Graphics and Applications, Oct 2006.
The Visual Computer, Volume 22, p713-720, Sept 2006.

In this paper, we present a new SH operation, called spherical harmonics scaling, to shrink or expand a spherical function in frequency domain. We show that this problem can be elegantly formulated as a linear transformation of SH projections, which is efficient to compute and easy to implement on a GPU. Spherical harmonics scaling is particularly useful for extrapolating visibility and radiance functions at a sample point to points closer to or farther from an occluder or light source. With SH scaling, we present applications to lowfrequency shadowing for general deformable object, and to efficient approximation of spherical irradiance functions within a mid-range illumination environment.

[ paper ] [ video ]

Experiences

  • Research Intern at Internet Graphics Group, Microsoft Research Asia (2004.10 - 2005.10)
    • mentor: Xin Tong
    • location: Beijing, P.R. China

Awards

  • Microsoft Fellowship, 2008

Links