Zhigeng Pan

Robust mesh watermarking based on multiresolution processing

Abstract In this paper we propose a new mesh watermarking scheme for triangle meshes, which are widely used in computer graphics systems. Arbitrary meshes lack a natural parameterization for frequency-based signal processing, and thus they are harder to be watermarked. In this paper, we adopt Guskov’s multiresolution signal processing method for meshes and use his 3D non-uniform relaxation operator to construct a Burt–Adelson pyramid for the mesh, and then watermark information is embedded into a suitable coarser mesh. Since all the computation and data structures are the same as those used in the multiresolution signal processing, our mesh watermarking algorithm can be integrated naturally with the multiresolution mesh processing toolbox. To detect watermarks, registration and resampling are needed to bring the attacked mesh model back into its original location, orientation, scale, topology and resolution level. Experimental results and attack analysis are given to show that our watermarking algorithm is robust under a variety of attacks, including vertex reordering, noise addition, simplification, filtering and enhancement, cropping, etc. Our main contribution to the field of 3D watermarking is that we propose a generic applicable multiresolution framework in which other proposed techniques may fit in as well.

Reliability Fusion of Time-of-Flight Depth and Stereo Geometry for High Quality Depth Maps

Time-of-flight range sensors have error characteristics, which are complementary to passive stereo. They provide real-time depth estimates in conditions where passive stereo does not work well, such as on white walls. In contrast, these sensors are noisy and often perform poorly on the textured scenes where stereo excels. We explore their complementary characteristics and introduce a method for combining the results from both methods that achieve better accuracy than either alone. In our fusion framework, the depth probability distribution functions from each of these sensor modalities are formulated and optimized. Robust and adaptive fusion is built on a pixel-wise reliability weighting function calculated for each method. In addition, since time-of-flight devices have primarily been used as individual sensors, they are typically poorly calibrated. We introduce a method that substantially improves upon the manufacturers calibration. We demonstrate that our proposed techniques lead to improved accuracy and robustness on an extensive set of experimental results.

Parallel genetic algorithms on programmable graphics hardware

Parallel genetic algorithms are usually implemented on parallel machines or distributed systems. This paper describes how fine-grained parallel genetic algorithms can be mapped to programmable graphics hardware found in commodity PC. Our approach stores chromosomes and their fitness values in texture memory on graphics card. Both fitness evaluation and genetic operations are implemented entirely with fragment programs executed on graphics processing unit in parallel. We demonstrate the effectiveness of our approach by comparing it with compatible software implementation. The presented approach allows us benefit from the advantages of parallel genetic algorithms on low-cost platform.

A real-time multi-cue hand tracking algorithm based on computer vision

Although hand tracking algorithm has been widely used in virtual reality and HCI system, it is still a challenging problem in vision-based research area. Due to the robustness and real-time requirements in VR applications, most hand tracking algorithms require special device to achieve satisfactory results. In this paper, we propose an easy-to-use and inexpensive approach to track the hands accurately with a single normal webcam. Outstretched hand is detected by contour & curvature based detection techniques to initialize the tracking region. Robust multi-cue hand tracking is then achieved by velocity-weighted features and color cue. Experiments show that the proposed multi-cue hand tracking approach achieves continuous real-time results even for the situation of cluttered background. The approach fulfills the speed and accuracy requirements of frontal-view vision-based human computer interactions.

A Review on Augmented Reality for Virtual Heritage System

Augmented reality is one of the emerging technologies to reconstruct the historical building and monument in the previous era, where the user experiences with the real environment or virtual scene. In education, Virtual Heritage becomes as a platform of learning, motivating and understanding of certain events and historical elements for the students and researchers. The significance of reconstruction of digital culture heritage are to preserve, protect and interpret of our cultural and history. In recent year, there are a number of significant researches and techniques that have been developed, which is focusing on virtual restitution of historical sites. This paper will present an overview on augmented reality in Virtual Heritage system and also consists with the explanation of techniques to reconstruct the historical sites.

Age invaders: social and physical inter-generational mixed reality family entertainment

Age invaders (AI), is a novel interactive intergeneration social-physical game which allows the elderly to play harmoniously together with children in the physical space, while parents can participate in the game play in real time remotely in the virtual world through the internet. Traditional digital games are designed for the young where normally the player sits in front of a computer or game console. Unlike standard computer games, age invaders brings the game play to a physical platform, and requires and encourages physical body movements rather than constraining the user in front of a computer for many hours. Age invaders is an interactive social-physical family digital game designed specially for a harmonious game play between the elderly and young. Adjusting game properties automatically compensates for potential elderly disadvantages, for example slower reaction time and slow movement.

A Bayes-Based Region-Growing Algorithm for Medical Image Segmentation

This paper discusses a new Bayesian-analysis-based region-growing algorithm for medical image segmentation that can robustly and effectively segment medical images. Specifically the approach studies homogeneity criterion parameters in a local neighbor region. Using the multislices Gaussian and anisotropic filters as a preprocess helps reduce an images noise. The algorithm framework is tested on CT and MRI image segmentation, and experimental results show that the approach is reliable and efficient.

A direct approach for subdivision surface fitting from a dense triangle mesh

Abstract This article presents a new and direct approach for fitting a subdivision surface from an irregular and dense triangle mesh of arbitrary topological type. All feature edges and feature vertices of the original mesh model are first identified. A topology- and feature-preserving mesh simplification algorithm is developed to further simplify the dense triangle mesh into a coarse mesh. A subdivision surface with exactly the same topological structure and sharp features as that of the simplified mesh is finally fitted from a subset of vertices of the original dense mesh. During the fitting process, both the position masks and subdivision rules are used for setting up the fitting equation. Some examples are provided to demonstrate the proposed approach.

An emotion model of 3d virtual characters in intelligent virtual environment

Human emotion is related to stimulus and cognitive appraisal. Emotion is very important to entertainment application of virtual reality. Emotion model of 3D virtual characters is a challenging branch of Intelligent Virtual Environment (IVE). A believable 3D character should be provided with emotion and perception. In general, a virtual character is regarded as an autonomous agent with sense, perception, behavior and action. An emotion model of 3D virtual characters on the basis of psychology theory is presented in this paper. Our work is to construct 3D virtual characters that have internal sensor and perception for external stimulus, and express emotion autonomously in real time. Firstly, architecture of a virtual character is set up by cognitive model; Secondly, emotion class is set up by OCC and Plutchik’s emotion theory; Thirdly, some new concepts about emotion are presented with a general mathematical model which is relation among emotion, stimulus, motivation variable, personality variable. Fourthly, a perception model of 3D characters by Gibson’s theory is introduced. As a result, an emotional animation demo system of 3D virtual character is implemented on PC.

Virtual learning environment for medical education based on VRML and VTK

Virtual reality (VR) is being applied to a wide range of medical areas, including medical education/training, surgery and diagnostics assistance. In the medical education field, VR opens new realms in the teaching of medicine and creates new effective learning procedures for the students. In contrast with the expensive immersive virtual reality learning environment (VRLE) such as CAVE, ImmersaDesk, virtual reality modeling language (VRML) technology provides a cheap and simple way to create such an environment and can be easily deployed in the classroom. In this paper, we describe some traditional application of VR in medical education and design a prototype of VRLE system based on VRML and visualization toolkit (VTK). The system architecture and module design are described in detail and some results are presented.