Efficient Affinity-based Edit Propagation using K-D Tree
Kun Xu, Yong Li , Tao Ju, Shi-Min Hu, Tian-Qiang Liu
Accepted by Siggraph Asia 2009.

Image/video editing by strokes has become increasingly popular due to the ease of interaction. Propagating the user inputs to the rest of the image/video, however, is often time and memory consuming especially for large data. We propose here an efficient scheme that allows affinity-based edit propagation to be computed on data containing tens of millions of pixels at interactive rate (in matter of seconds). The key in our scheme is a novel means for approximately solving the optimization problem involved in edit propagation, using adaptive clustering in a high-dimensional, affinity space. Our approximation significantly reduces the cost of existing affinity-based propagation methods while maintaining visual fidelity, and enables interactive stroke-based editing even on high resolution images and long video sequences using commodity computers.

[ paper ] [ video ]

Edit Propagation on Bidirectional Texture Functions
Kun Xu, Jiaping Wang, Xin Tong, Shi-Min Hu, Baining Guo
Accepted by Pacific Graphics 2009.

We propose an efficient method for editing bidirectional texture functions (BTFs) based on edit propagation scheme. In our approach, users specify sparse edits on a certain slice of BTF. An edit propagation scheme is then applied to propagate edits to the whole BTF data. The consistency of the BTF data is maintained by propagating similar edits to points with similar underlying geometry/reflectance. For this purpose, we propose to use view independent features including normals and re?ectance features reconstructed from each view to guide the propagation process. We also propose an adaptive sampling scheme for speeding up the propagation process. Since our method needn’t any accurate geometry and re?ectance information, it allows users to edit complex BTFs with interactive feedback.

[ paper ] [ video ]

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), 2008.

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 ]