International Journal of Image and Graphics

In cases of densely occluded urban scenes, it is useful to determine the visibility of scenes, since only small parts of the scene are visible from a given cell. In this paper, we introduce a new visibility preprocessing method that efficiently computes potentially visible objects for volumetric cells. The proposed method deals with general 3D polygonal models and invisible objects jointly blocked by multiple occluders. The proposed approach decomposes volume visibility into a set of point visibilities, and then computes point visibility using hardware-visibility queries. We carry out experiments on various large-scale scenes, and show the performance of our algorithm. Our performance analysis approach estimates the exact solution of volume visibility. From differences between the estimated solution and the proposed algorithms solution, we show that our algorithm seeks a tight overestimate of the potentially visible set (PVS).

In this paper, we present a new Monte Carlo computational way for solving the global illumination problem whereby plenty of unbiased estimators can be employed to enrich the solutions leading to simple error control and faster estimation. Especially so, the zero variance importance sampling procedure can be exploited to calculate the global illumination optimally. Based on the new scheme, a new Monte Carlo global illumination algorithm and its importance driven version have been developed and carried out. Results, which have been obtained by rendering test scenes, show that this new framework is promising.

This paper presents a public mesh watermarking algorithm whereby the resultant watermarked image minus the original image is the watermark information. According to the addition property of the Fourier transform, a change of spatial domain will cause a change in the frequency domain. The watermark information is then scaled down and embedded in one part of the x-coordinate of the original mesh. Finally, the x-coordinate of the test mesh is amplified before extraction. Experimental results prove that our algorithm is resistant to a variety of attacks without the need for any preprocessing.

Virtual Reality leads Digital Product Development technology to a more effective and convenient way by presenting the product model in an immersive real 3D environment. Distributed VR even enables partners to discuss the design of the product independent of their locations. This paper introduces our work with a Digital Product Development System with Virtually Cooperating Teams Using High Bandwidth Networks — ProViT, which aims at building up immersive telepresence systems for design review across high-bandwidth networks. Video and audio streaming are integrated in the virtual environment to support immersive teleconference aspects of the distributed design review sessions. A network management system has been developed for the supervision, maintenance and processing of distributed setups, and network security.

This paper presents interfacing techniques to integrate a virtual environment (VE), computer graphics, image-based modeling, and other technologies in a networked system for robot control. Technologies such as networked robotics have advanced rapidly in the past decade, bringing a physical aspect to the usage of the Internet. Various applications of Internet telerobotics have been investigated and a variety of techniques have been proposed to increase the control robustness and efficiency of such systems. In this paper, we introduce a teleoperated robot manipulator that uses VE and other supporting technologies as a human-system interface to suppress the variable communication latency of the Internet. The paper focuses on the control techniques and the system structure that supports the implementation of the techniques.

This article introduces a reflection about behavioral specification for interactive and participative agent-based simulation in virtual reality. Within this context, it is necessary to reach a high level of expressiveness in order to enforce interactions between the designer and the behavioral model during the in-line prototyping. It is required to consider the needs of semantic very early in the design process. The intentional agent model is exposed here as a possible answer. It relies on a mixed imperative and declarative approach which focuses on the link between decision and action. The design of a tool able to simulate virtual environment implying agents based on this model is discussed.

This paper investigates the performance of a bimodal biometric system using fusion of shape and texture. We propose several new hand shape features that can be used to represent the hand shape and improve the performance for hand shape based user authentication. We also demonstrate the usefulness of Discrete Cosine Transform (DCT) coefficients for palmprint authentication. The score level fusion of hand shape and palmprint features using product rule achieves best performance as compared to Max or Sum rule. However the decisions from the Sum, Max, and Product rules can also be combined to further enhance the performance. Thus the fusion of score level decisions, from the multiple strategies, is proposed and investigated. The two hand shapes of an individual are anatomically similar. However, the palmprints from two hands can be combined to further improve performance and is demonstrated in this paper.

This paper investigates adult images detection based on the shape features of skin regions. In order to accurately detect skin regions, we propose a skin detection method using multi-Bayes classifiers in the paper. Based on skin color detection results, shape features are extracted and fed into a boosted classifier to decide whether or not the skin regions represent a nude. We evaluate adult image detection performance using different boosted classifiers and different shape descriptors. Experimental results show that classification using boosted C4.5 classifier and combination of different shape descriptors outperforms other classification schemes.

Facial expression recognition technology plays an important role in research areas such as psychological studies, image understanding and virtual reality etc. In order to achieve subject-independent facial expression recognition and obtain robustness against illumination variety and image deformation, facial expression recognition methods based on Gabor wavelet transformation and elastic templates matching are presented in this paper. First given a still image containing facial expression information, preprocessors are executed which include gray and scale normalization. Secondly, Gabor wavelet filters are adopted to extract expression features. Then the elastic graph for expression features is constructed. Finally, elastic templates matching algorithm and K-nearest neighbors classifier are used to recognize facial expression. Experiments show that expression features can be extracted effectively by Gabor wavelet transformation, which is insensitive to illumination variety and individual difference, and high recognition rate can be obtained using elastic templates matching algorithm, which is subject-independent.

Human tastes in art motivate the need for effective means to build a visual mosaic picture which is made up of many small tiles. In some previous work researchers have tried to translate pictures' styles.¹ In this paper, a new approach to image processing in arts is presented in the domain of generating a series of artistic mosaic pictures. An arbitrary image is first translated into a mosaic-based one by dividing it into a number of sub-blocks each with the mean value of the pixels in it. Each of these small fragments can be assigned a new location within this image so that a new mosaic picture is generated. By this mean, images with similar color features can be used to create a series of mosaic pictures. The mosaic pictures consist of the same elements as each other, but might be extremely different from the semantic contents. A basic algorithm is presented, followed by some further improvements. Some preliminary experimental results are then given to show the impact of the proposed special techniques.