In this paper, a novel motion texture approach is presented for synthesizing long character motion (e.g., kungfu) that is similar to the original short input motion. First, a new motion with repeated frames is generated by exploiting the symmetric properties of the frames and reversing the motion sequence playback in a given motion sequence. Then, the order of the above motion sequence is rearranged by putting the start and the end frames together. The graphcut algorithm is used to seamlessly synthesize the transition between the start and the end frames, which is noted as graphcut-based motion-texton. Finally, we utilize the motion-textons to synthesize long motion texture, which can be patched together like the image texture synthesis method using graphcut algorithm, and automatically form a long motion texture endlessly. Our approach is demonstrated by synthesizing the long kungfu motion texture without visual artifacts, together with post-processing including our new developed graphcut-based motion blending and Poisson-based motion smoothing techniques.

This paper presents a method for tracing a planar implicit curve f(x, y)=0 on a rectangular region based on continuation scheme. First, according to the starting track-point and the starting track-direction of the curve, make a new function F(x, y)=0 where the same curve with f(x, y)=0 is defined. Then we trace the curve between the two domains where F(x, y)>0 and F(x, y)<0 alternately, according to the two rules presented in this paper. Equal step size or adaptive step size can be used, when we trace the curve. An irregular planar implicit curve (such as the curve with large curvatures at some points on the curve), can be plotted if an adaptive step size is used. Moreover, this paper presents a scheme to search for the multiple points on the curve. Our method has the following advantages: (1) it can plot C⁰ planar implicit curves; (2) it can plot the planar implicit curves with multiple points; (3) by the help of using the two rules, our method does not need to compute the tangent vector at the points on the curve, and directly searches for the direction of the tracing curve; (4) the tracing procedure costs only one of two evaluations of function f(x, y)=0 per moving step, while most existing similar methods cost more evaluations of the function.

As an audiovisual medium, computer animations require superior image quality and professional soundtrack to lead audiences into their fascinating virtual world. Without sound, the impact of storytelling is reduced or the story is even not understandable. Despite the importance of sound, most animators are unfamiliar with sound editing software. Limited budget projects such as independent or student works have difficulty hiring sound professionals to create tailor-made soundtrack. Therefore, we need a suitable sound tool to express their individual ideas. In this paper, we propose an approach using schematic for both computer animation and sound. Our approach provides (1) physical simulation on sound through animation parameters and (2) a new channel for animators to add aesthetic values in sound through their experience of using schematics in existing animation software. We demonstrate our idea through several examples, such as Doppler shift, obstacle effect, importance, energetic, and sputtering effect.

We present an approach for generating paintings on photographic images with the style encoded by the example paintings and adopt representative brushes extracted from the example paintings as the painting primitives. Our system first divides the given photographic image into several regions on which we synthesize a grounding layer with texture patches extracted from the example paintings. Then, we paint those regions using brushes stochastically chosen from the brush library, with further brush color and shape perturbations. The brush direction is determined by a direction field either constructed by a convenient user interactive manner or synthesized from the examples. Our approach offers flexible and intuitive user control over the painting process and style.

In this paper, a novel approach is proposed for denoising of Chinese calligraphy tablet documents. The method includes two phases: First, a partial differential equations (PDE) based the total variation model and Otsu thresholding method are used to preprocess the calligraphy document image. Second, a new method based on run-length statistics and structure characteristics of Chinese characters is proposed to remove some random and ant-like noises. This includes the optimal threshold selection from histogram of run-length probability density, and improved Hough transform algorithm for line shape noise detection and removal. Examples are given in the paper to demonstrate the proposed method.

A mesh editing framework is presented in this paper, which integrates Free-Form Deformation (FFD) and geometry signal processing. By using simplified model from original mesh, the editing task can be accomplished with a few operations. We take the deformation of the proxy and the position coordinates of the mesh models as geometry signal. Wavelet analysis is employed to separate local detail information gracefully. The crucial innovation of this paper is a new adaptive regular sampling approach for our signal analysis based editing framework. In our approach, an original mesh is resampled and then refined iteratively which reflects optimization of our proposed spectrum preserving energy. As an extension of our spectrum editing scheme, the editing principle is applied to geometry details transferring, which brings satisfying results.

Recently unstructured dense point sets have become a new representation of geometric shapes. In this paper we introduce a novel framework within which several usable error metrics are analyzed and the most basic properties of the progressive point-sampled geometry are characterized. Another distinct feature of the proposed framework is its compatibility with most previously proposed surface inference engines. Given the proposed framework, the performances of four representative well-reputed engines are studied and compared.

Curvature tells much about details of surfaces and is studied widely by researchers in the computer graphics community. In this paper, we first explain the mean-curvature view of Dirichlet energy of triangular surfaces and introduce a curvature representation of details, and then present surfaces editing applications based on their curvature representation. We apply our method to surfaces with complex boundaries and rich details. Results show the validity and robustness of our method and demonstrate curvature map can be a helpful surfaces detail representation.

The new free-form surface modelling technology for robotic belt grinding simulation presented in this paper is based on discrete surfel elements generated from the surface approximation point set and can facilitate the simulation implementation. A local process model exploits the advantage of surfel representation to compute the material removal rate and the final surface grinding error can be easily carried out. With the help of this system, robot programmers can improve the path planning and predict potential problems by visualizing the manufacturing process.

A method for computing the visible regions of free-form surfaces is proposed in this paper. Our work is focused on accurately calculating the visible regions of the sequenced rational Bézier surfaces forming a solid model and having coincident edges but no inner-intersection among them. The proposed method calculates the silhouettes of the surfaces without tessellating them into triangle meshes commonly used in previous methods so that arbitrary precision can be obtained. The computed silhouettes of visible surfaces are projected onto a plane orthogonal to the parallel light. Then their spatial relationship is applied to calculate the boundaries of mutual-occlusion regions. As the connectivity of the surfaces on the solid model is taken into account, a surface clustering technique is also employed and the mutual-occlusion calculation is accelerated. Experimental results showed that our method is efficient and robust, and can also handle complex shapes with arbitrary precision.

A novel reconstruction method from contours lines is provided. First, we use a simple method to get rid of redundant points on every contour, then we interpolate them by using cubic Bézier spline curve. For corresponding points of different contours, we interpolate them by the cubic Bézier spline curve too, so the whole surface can be reconstructed by the bi-cubic Bézier spline surface. The reconstructed surface is smooth because every Bézier surface is patched with G² continuity, the reconstruction speed is fast because we can use the forward elimination and backward substitution method to solve the system of tridiagonal equations. We give some reconstruction examples at the end of this paper. Experiments showed that our method is applicable and effective.

This paper presents a novel system assisting medical dementia examination in a joyful way: the object just needs to play a popular game SSC against the computer during the examination. The SSC game’s target is to detect the player’s reacting capability, which is related closely with dementia. Our system reaches this target with some advantages: there are no temporal and spatial constraints at all. There is no cost, and it can even improve people’s mental status. Hand talk technology and EHMM gesture recognition approach are employed to realize the human computer interface. Experiments showed that this system can evaluate people’s reacting capability effectively and is helpful for initial dementia examination.

We present a method of 3D image mosaicing for real 3D representation of roadside buildings, and implement a Web-based interactive visualization environment for the 3D video mosaics created by 3D image mosaicing. The 3D image mosaicing technique developed in our previous work is a very powerful method for creating textured 3D-GIS data without excessive data processing like the laser or stereo system. For the Web-based open access to the 3D video mosaics, we build an interactive visualization environment using X3D, the emerging standard of Web 3D. We conduct the data preprocessing for 3D video mosaics and the X3D modeling for textured 3D data. The data preprocessing includes the conversion of each frame of 3D video mosaics into concatenated image files that can be hyperlinked on the Web. The X3D modeling handles the representation of concatenated images using necessary X3D nodes. By employing X3D as the data format for 3D image mosaics, the real 3D representation of roadside buildings is extended to the Web and mobile service systems.

We propose a high-performance path planning algorithm for automatic target tracking in the applications of real-time simulation and visualization of large-scale terrain datasets, with a large number of moving objects (such as vehicles) tracking multiple moving targets. By using a modified Dijkstra’s algorithm, an optimal path between each vehicle-target pair over a weighted grid-presented terrain is computed and updated to eliminate the problem of local minima and losing of tracking. Then, a dynamic path re-planning strategy using multi-resolution representation of a dynamic updating region is proposed to achieve high-performance by trading-off precision for efficiency, while guaranteeing accuracy. Primary experimental results showed that our algorithm successfully achieved 10 to 96 frames per second interactive path-replanning rates during a terrain simulation scenario with 10 to 100 vehicles and multiple moving targets.

Realistic modeling and rendering of dynamic tornado scene is recognized as a challenging task for researchers of computer graphics. In this paper a new physically based method for simulating and animating tornado scene is presented. We first propose a Two-Fluid model based on the physical theory of tornado, then we simulate the flow of tornado and its interaction with surrounding objects such as debris, etc. Taking the scattering and absorption of light by the participating media into account, the illumination effects of the tornado scene can be generated realistically. With the support of graphics hardware, various kinds of dynamic tornado scenes can be rendered at interactive rates.

Use of compressed mesh in parallel rendering architecture is still an unexplored area, the main challenge of which is to partition and sort the encoded mesh in compression-domain. This paper presents a mesh compression scheme PRMC (Parallel Rendering based Mesh Compression) supplying encoded meshes that can be partitioned and sorted in parallel rendering system even in encoded-domain. First, we segment the mesh into submeshes and clip the submeshes’ boundary into Runs, and then piecewise compress the submeshes and Runs respectively. With the help of several auxiliary index tables, compressed submeshes and Runs can serve as rendering primitives in parallel rendering system. Based on PRMC, we design and implement a parallel rendering architecture. Compared with uncompressed representation, experimental results showed that PRMC meshes applied in cluster parallel rendering system can dramatically reduce the communication requirement.

In this paper we present a novel method for dividing and clustering large volumetric scalar out-of-core datasets. This work is based on the Ordered Cluster Binary Tree (OCBT) structure created using a top-down or divisive clustering method. The OCBT structure allows fast and efficient sub volume queries to be made in combination with level of detail (LOD) queries of the tree. The initial partitioning of the large out-of-core dataset is done by using non-axis aligned planes calculated using Principal Component Analysis (PCA). A hybrid OCBT structure is also proposed where an in-core cluster binary tree is combined with a large out-of-core file.

Environment matting and compositing is a technique to extract a foreground object, including color, opacity, reflective and refractive properties, from a real-world scene, and synthesize new images by placing it into new environments. The description of the captured object is named environment matte. Recent matting and compositing techniques can produce quite realistic images for objects with complex optical properties. This paper presents an approximate method to transform the matte by simulating variation of the foreground object’s refractive index. Our algorithms can deal with achromatous-and-transparent objects and the experimental results are visually acceptable. Our idea and method can be applied to produce some special video effects, which could be very useful in film making, compared with the extreme difficulty of physically changing an object’s refractive index.

Homogeneous matrices are widely used to represent geometric transformations in computer graphics, with interpolation between those matrices being of high interest for computer animation. Many approaches have been proposed to address this problem, including computing matrix curves from curves in Euclidean space by registration, representing one-parameter curves on manifold by rational representations, changing subdivisional methods generating curves in Euclidean space to corresponding methods working for matrix curve generation, and variational methods. In this paper, we propose a scheme to generate rational one-parameter matrix curves based on exponential map for interpolation, and demonstrate how to obtain higher smoothness from existing curves. We also give an iterative technique for rapid computing of these curves. We take the computation as solving an ordinary differential equation on manifold numerically by a generalized Euler method. Furthermore, we give this algorithm’s bound of the error and prove that the bound is proportional to the shift length when the shift length is sufficiently small. Compared to direct computation of the matrix functions, our Euler solution is faster.

Conventional color-printing systems often use inks of three hues, such as CMY, CMYK and CMYKLcLm, but in order to obtain more realistic color reproductions, the ink set of more than three hues has been adopted by some color-printing systems. It is difficult, however, to model the composed color with the multiple inks when the number of the output ink hues exceeds three due to the none-unique mapping between the color spaces of the CIE Lab and the multi-color printing device. In this paper, we propose a fine color-printing method for multi-color printing device with the ink set of more than three hues. The proposed approach has good color expression ability and provides fine control of the printed color. By dividing the output color space into several subspaces, our method allows one-to-one mapping between the standard color space and the multi-color output color space. It has been proved effective when applied to the digital inkjet printer—Mutoh8000.

Most collision detection algorithms can be efficiently used only with solid and rigid objects, for instance, Hierarchical methods which must have their bounding representation recalculated every time deformation occurs. An alternative algorithm using particle-based method is then proposed which can detect the collision among non-rigid deformable polygonal models. However, the original particle-based collision detection algorithm might not be sufficient enough in some situations due to the improper particle dispersion. Therefore, this research presents an improved algorithm which provides a particle to detect in each separated area so that particles always covered all over the object. The surface partitioning can be efficiently performed by using LBG quantization since it can classify object vertices into several groups base on a number of factors as required. A particle is then assigned to move between vertices in a group by the attractive forces received from other particles on neighbouring objects. Collision is detected when the distance between a pair of corresponding particles becomes very small. Lastly, the proposed algorithm has been implemented to show that collision detection can be conducted in real-time.

In this paper, a novel component-based scene graph is proposed, in which all objects in the scene are classified to different entities, and a scene can be represented as a hierarchical graph composed of the instances of entities. Each entity contains basic data and its operations which are encapsulated into the entity component. The entity possesses certain behaviours which are responses to rules and interaction defined by the high-level application. Such behaviours can be described by script or behaviours model. The component-based scene graph in the paper is more abstractive and high-level than traditional scene graphs. The contents of a scene could be extended flexibly by adding new entities and new entity components, and behaviour modification can be obtained by modifying the model components or behaviour scripts. Its robustness and efficiency are verified by many examples implemented in the Virtual Scenario developed by Peking University.

This paper introduces a novel method for estimating the skeleton proportions of a human figure from monocular data. The proposed system will first automatically extract the key frames and recover the perspective camera model from the 2D data. The human skeleton proportions are then estimated from the key frames using the recovered camera model without posture reconstruction. The proposed method is tested to be simple, fast and produce satisfactory results for the input data. The human model with estimated proportions can be used in future research involving human body modeling or human motion reconstruction.

Facial expression recognition consists of determining what kind of emotional content is presented in a human face. The problem presents a complex area for exploration, since it encompasses face acquisition, facial feature tracking, facial expression classification. Facial feature tracking is of the most interest. Active Appearance Model (AAM) enables accurate tracking of facial features in real-time, but lacks occlusions and self-occlusions. In this paper we propose a solution to improve the accuracy of fitting technique. The idea is to include occluded images into AAM training data. We demonstrate the results by running experiments using gradient descent algorithm for fitting the AAM. Our experiments show that using fitting algorithm with occluded training data improves the fitting quality of the algorithm.