任重 图形学 绘制 图形处理单元 真实感 软影Associate Researcher
Before returning to the State Key Lab of CAD&CG, Zhejiang University in Apr. 2010, I spent a happy five years in the Internet Graphics Group, Microsoft Research Asia, first as an intern then as an associate researcher. 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-based methods in interactive global illumination. During the past several years, I've been really fortunate to work with ZHOU Kun, John Snyder, HUA Wei, HOU Qiming, SUN Xin, GONG Minmin, GUO Baining, BAO Hujun, WANG Rui, Steve Lin, Peter-Pike Sloan, LIU Xinguo, Harry Shum, LI Tengfei 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.
- IPC member: Pacific Graphics 2010
- reviewer: ACM SIGGRAPH Asia 2008/2010-2011, IEEE Vis 2010, PG 2009-2011, EG 2009, ESPGV 2011, TVCG, TOG, CGF, C&G, JCAD.
- introduce the analytic form of non-linear rays in refractive media with constant refractive index gradient, based on which a ray tracing algorithm is developed;
- extend the algorithm to general non-constant refractive media through tetrahedra-based representation or voxel-based representation;
- derive the analytic form of non-linear rays in mirages.
- analytic forms of rays and fold points;
- larger tracing steps, leading to superior performance.
- no simple analytic form for ray-scene intersections, need to resort to numeric methods;
- piece-wise linear approxiation of refractive index function, may require inpractical large number of tetra for very complex functions.
downloadable:
- decouple light integration complexity from light transport complexity;
- model environment light with a set of SRBFs;
- address light integration complexity by precomputation;
- handle self shadowing by convolution optical depth map;
- handle mutiple scattering by dual scattering and sparse sampling and interpolation.
- the first interactive hair rendering algorithm under environment lighting;
- support light animation;
- support dynamic hair volume.
- precomputation per scattering function;
- ignore eccentricity in the scattering function.
downloadable:
- tabulate per-vertex transfer from global incident directions to local incident directions;
- use biclutering to directly compress the transfer matrix.
- all-frequency biscale transfer, support highly-detailed surface under env-lighting;
- high compression ratio with no quality lost;
- operates directly on pixel basis, fully dynamic env-lighting can be directly supported.
- static scene geometry;
- rather costly pre-computation(~1 hour).
downloadable:
- move all stages of basic Reyes pipeline to GPU;
- introduce a dynamic stage scheduling algorithm to maximize the available parallelism at each individual stage of the pipeline while keeping data in GPU memory;
- minimize inter-GPU communication by a multi-GPU scheduling algorithm based on work stealing, which can be easily combined with the stage scheduling algorithm above;
- implemented with BSGP.
- could be the fastest Reyes renderer on PCs;
- support multi-GPU and out-of-core texture;
- quality is comparable with PRMan.
- system will fail if the grids and their bounding boxes do not fit into the vram;
- currently only support basic Reyes features. no ray tracing, no photon mapping...(coming soon)
downloadable:
source code, test scenes
- 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.
- 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.
- single-scattering only (though it's possible to be combined with the technique below to incorporate multiple-scattering);
- constant phase function.
downloadable:
- 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.
- 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.
- low-frequency lighting, can't handle strongly directional phase functions;
- can't handle real dynamic medium due to the need for precomputation.
downloadable:
- approximate block geometry with sphere blockers;
- 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.
- 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.
- 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)
downloadable:
paper(2.4MB), video(49.7MB), slides(31.9MB), supplements(3.1MB), test data#1(tumbling man)(8.9MB), test data#2(walking man)(5.2MB), test data#3(slipped walking man)(1.5MB), test data format, bibtex, visibility sample
- tabulate the intersection of scene geometries in a 4D line space to form i-fields;
- use visibility query & splatting in parameter space to accelerate run-time computation;
- use photon splatting in parameter space to compute indirect bounces.
- visibility query made fast;
- fast scan-line conversion for i-field generation;
- reuse i-field for object instancing and object transformation.
- no compression, scalability is low;
- limited shadowing feature reprensentability due to line space resolution.
downloadable:
downloadable: