Volume 13,Issue 9,2002 Table of Contents
2002, 13(9):1741-1756.
Abstract:
Transmit power control is central technique for resource and interference management in Ad hoc wireless network. While power control has been traditionally considered as a means to counteract the harmful effect of channel fading, the more general emerging view is that it is a flexible mechanism to provide quality of service for individual users. In this paper, a novel adaptive clustering algorithm is presented in order to alleviate the dynamic characteristics of network topology and economize the power energy simultaneously. This proposal is a GPS based mechanism. By predicting the next location of mobile host with its historic trajectory, it adjusts its transmit power in advance. In order to maximize the throughput of network, it controls all clusters in suitable size adaptively. Experiments on GlomoSim have been conducted. The results show that clustering approach proposed in this paper is a practically valuable topology management mechanism for ad hoc wireless networks, especially for mobile networks composed of high-speed mobile hosts.
Transmit power control is central technique for resource and interference management in Ad hoc wireless network. While power control has been traditionally considered as a means to counteract the harmful effect of channel fading, the more general emerging view is that it is a flexible mechanism to provide quality of service for individual users. In this paper, a novel adaptive clustering algorithm is presented in order to alleviate the dynamic characteristics of network topology and economize the power energy simultaneously. This proposal is a GPS based mechanism. By predicting the next location of mobile host with its historic trajectory, it adjusts its transmit power in advance. In order to maximize the throughput of network, it controls all clusters in suitable size adaptively. Experiments on GlomoSim have been conducted. The results show that clustering approach proposed in this paper is a practically valuable topology management mechanism for ad hoc wireless networks, especially for mobile networks composed of high-speed mobile hosts.
2002, 13(9):1757-1764.
Abstract:
At Auscrypt'92, Harn and Yang first proposed the conception of (t,n) threshold undeniable signature, in which only subsets with at least t members can represent a group to generate, confirm or disavow a signature. Later, several schemes are proposed, but none of them is secure. So up to now, how to design a secure (t,n) threshold undeniable signature scheme is remained an open problem. In this paper, based on discrete logarithm cryptosystem, a secure and efficient (t,n) threshold undeniable signature scheme without a trusted party is presented. This scheme has an attractive property that member's honesty is verifiable because a publicly verifiable secret sharing scheme is used to distribute secrets and two discrete logarithm equality protocols are used to provide necessary proofs of correctness, which are proposed by Schoenmakers at Crypto'99.
At Auscrypt'92, Harn and Yang first proposed the conception of (t,n) threshold undeniable signature, in which only subsets with at least t members can represent a group to generate, confirm or disavow a signature. Later, several schemes are proposed, but none of them is secure. So up to now, how to design a secure (t,n) threshold undeniable signature scheme is remained an open problem. In this paper, based on discrete logarithm cryptosystem, a secure and efficient (t,n) threshold undeniable signature scheme without a trusted party is presented. This scheme has an attractive property that member's honesty is verifiable because a publicly verifiable secret sharing scheme is used to distribute secrets and two discrete logarithm equality protocols are used to provide necessary proofs of correctness, which are proposed by Schoenmakers at Crypto'99.
2002, 13(9):1765-1772.
Abstract:
Moments and invariant moments are important features used in identification and inspection of industrial parts. It is necessary to compute geometric moment's values in real-time rate. The efficient computation of two-dimensional geometric moments on gray-level images is addressed in this paper. Despite the existence of many algorithms of fast computation of moments, it cannot be implemented for real-time computation to be run on a PC without the use of some special dedicated hardware tools. The reason beyond this is that those fast algorithms do reduce the complexity of computing but still one needs to use floating-point arithmetic operations in the computation process. To achieve real-time computation on a PC machine, what the algorithm suggested here is based on dividing the image into equally sized blocks. This algorithm works by computing local moments at each block using integer operations, then accumulating the total image moments with floating-point operations. With this computation scheme no approximation is used, it is an exact computation. Overcoming this overflow problem, however, is not straightforward without using some kind of transformation to each block. Hatamian's (improved) filter is used to compute those block moments (BLMs) efficiently. The experiments show that the algorithm presented in the paper has greatly reduced floating-point operations in fast computation of moments, and greatly improved the speed of the computation of moments. The new algorithm can be effectively used in real-time identification and inspection of complicated industrial parts.
Moments and invariant moments are important features used in identification and inspection of industrial parts. It is necessary to compute geometric moment's values in real-time rate. The efficient computation of two-dimensional geometric moments on gray-level images is addressed in this paper. Despite the existence of many algorithms of fast computation of moments, it cannot be implemented for real-time computation to be run on a PC without the use of some special dedicated hardware tools. The reason beyond this is that those fast algorithms do reduce the complexity of computing but still one needs to use floating-point arithmetic operations in the computation process. To achieve real-time computation on a PC machine, what the algorithm suggested here is based on dividing the image into equally sized blocks. This algorithm works by computing local moments at each block using integer operations, then accumulating the total image moments with floating-point operations. With this computation scheme no approximation is used, it is an exact computation. Overcoming this overflow problem, however, is not straightforward without using some kind of transformation to each block. Hatamian's (improved) filter is used to compute those block moments (BLMs) efficiently. The experiments show that the algorithm presented in the paper has greatly reduced floating-point operations in fast computation of moments, and greatly improved the speed of the computation of moments. The new algorithm can be effectively used in real-time identification and inspection of complicated industrial parts.
2002, 13(9):1773-1778.
Abstract:
In a multi robots environment, the overlap of actions selected by each robot makes the acquisition of cooperation behaviors less efficient. In this paper an approach is proposed to determine the action selection priority level based on which the cooperative behaviors can be readily controlled. First, eight levels are defined for the action selection priority, which can be correspondingly mapped to eight subspaces of actions. Second, using the local potential field method, the action selection priority level for each robot is calculated and thus its action subspace is obtained. Then, Reinforcement learning (RL) is utilized to choose a proper action for each robot in its action subspace. Finally, the proposed method has been implemented in a soccer game and the high efficiency of the proposed scheme was verified by the result of both the computer simulation and the real experiments.
In a multi robots environment, the overlap of actions selected by each robot makes the acquisition of cooperation behaviors less efficient. In this paper an approach is proposed to determine the action selection priority level based on which the cooperative behaviors can be readily controlled. First, eight levels are defined for the action selection priority, which can be correspondingly mapped to eight subspaces of actions. Second, using the local potential field method, the action selection priority level for each robot is calculated and thus its action subspace is obtained. Then, Reinforcement learning (RL) is utilized to choose a proper action for each robot in its action subspace. Finally, the proposed method has been implemented in a soccer game and the high efficiency of the proposed scheme was verified by the result of both the computer simulation and the real experiments.
2002, 13(9):1779-1786.
Abstract:
Magnetic Resonance Image (MRI) segmentation plays a major role in the tissue quantitative analysis which benefits the early treatment of neurological diseases. In this paper, a new approach to MRI segmentation based on hierarchical Markov random field (MRF) model is proposed: In higher-level MRF, a new mixture model is presented to describe the label image, that is, the interior of region is modeled by homogenous and isotropic MRF while the boundary is modeled by inhomogeneous and anisotropic MRF. So the orientation is incorporated into the boundary information and the characteristic of label image can be more accurately represented. In lower-level MRF, the different Gauss texture is filled in each region to describe pixel image. Then the segmentation problem is formulated as Maximum a Posterior Probability (MAP) estimation rule. A histogram based DAEM algorithm is used, which is able to find the global optima of the standard finite normal mixture (SFNM) parameters. Based on the meaning of prior MRF parameter, an approximate method is proposed to simplify the estimation of those parameters. Experiments on the pathological MRI show that our approach can achieve better results.
Magnetic Resonance Image (MRI) segmentation plays a major role in the tissue quantitative analysis which benefits the early treatment of neurological diseases. In this paper, a new approach to MRI segmentation based on hierarchical Markov random field (MRF) model is proposed: In higher-level MRF, a new mixture model is presented to describe the label image, that is, the interior of region is modeled by homogenous and isotropic MRF while the boundary is modeled by inhomogeneous and anisotropic MRF. So the orientation is incorporated into the boundary information and the characteristic of label image can be more accurately represented. In lower-level MRF, the different Gauss texture is filled in each region to describe pixel image. Then the segmentation problem is formulated as Maximum a Posterior Probability (MAP) estimation rule. A histogram based DAEM algorithm is used, which is able to find the global optima of the standard finite normal mixture (SFNM) parameters. Based on the meaning of prior MRF parameter, an approximate method is proposed to simplify the estimation of those parameters. Experiments on the pathological MRI show that our approach can achieve better results.
2002, 13(9):1787-1795.
Abstract:
To further enhance the security of the present digital watermarking, the reversibility of widely researched adaptive watermarking is investigated. First, watermarking schemes are classified and generalized. Then, on the assumption that adaptive watermarking places no constraint on the formation of watermarks and scaling factors, the reversibility and quasi-reversibility, together with their resulting reverse and quasi-reverse engineering attacks, which could disturb or even overturn the ownership verification, are defined, analyzed and illustrated. Finally, the necessity of placing constraints on the formation of watermarks and scaling factors is concluded, and the essential irreversibility of some adaptive technologies, which can be used to enhance the security, is pointed out. Making watermarks and scaling factors one-way dependent on original data, and exploiting the human perceptual system, help watermarking become resistant to the above attacks and more reliable in ownership verification.
To further enhance the security of the present digital watermarking, the reversibility of widely researched adaptive watermarking is investigated. First, watermarking schemes are classified and generalized. Then, on the assumption that adaptive watermarking places no constraint on the formation of watermarks and scaling factors, the reversibility and quasi-reversibility, together with their resulting reverse and quasi-reverse engineering attacks, which could disturb or even overturn the ownership verification, are defined, analyzed and illustrated. Finally, the necessity of placing constraints on the formation of watermarks and scaling factors is concluded, and the essential irreversibility of some adaptive technologies, which can be used to enhance the security, is pointed out. Making watermarks and scaling factors one-way dependent on original data, and exploiting the human perceptual system, help watermarking become resistant to the above attacks and more reliable in ownership verification.
2002, 13(9):1796-1803.
Abstract:
A hybrid representation of environment models is proposed by combining points and polygons through which a real time walkthrough of a complex environment can be achieved. Starting from multiple depth reference images, the pixels of images are classified into two categories, corresponding to the planar and non-planar surfaces in 3D space. For the pixels corresponding to the planar surfaces, the plane coefficients are reconstructed and all their appearances in the reference images are merged to form uniform-sampled texture images by a comparison of sampling rate and resampling.For the pixels coresponding to the non-planar surfaces,their point representation is kept and no 3D models are reconstructed,the redundant pixels are removed by sampling rate comparison.The remained pixels are organized by OBB-tree according to their space coordinates.At the same time,the holes that are unable to be captured by all the reference images are pre-filled in the preprocessing phase so that the probability of hole appearance in walkthrough is greatly reduced.Under this hybrid representation,texture mapping and point warping are employed to render the novel views,to take full advantages of acceleration utility of graphics hardware.
A hybrid representation of environment models is proposed by combining points and polygons through which a real time walkthrough of a complex environment can be achieved. Starting from multiple depth reference images, the pixels of images are classified into two categories, corresponding to the planar and non-planar surfaces in 3D space. For the pixels corresponding to the planar surfaces, the plane coefficients are reconstructed and all their appearances in the reference images are merged to form uniform-sampled texture images by a comparison of sampling rate and resampling.For the pixels coresponding to the non-planar surfaces,their point representation is kept and no 3D models are reconstructed,the redundant pixels are removed by sampling rate comparison.The remained pixels are organized by OBB-tree according to their space coordinates.At the same time,the holes that are unable to be captured by all the reference images are pre-filled in the preprocessing phase so that the probability of hole appearance in walkthrough is greatly reduced.Under this hybrid representation,texture mapping and point warping are employed to render the novel views,to take full advantages of acceleration utility of graphics hardware.
2002, 13(9):1804-1812.
Abstract:
A progressive geometry compression scheme is presented in this paper. In this scheme, a mesh is represented as a base mesh followed by some groups of vertex split operations using an improved simplification method, in which each level of the mesh can be refined into the next level by carrying out a group of vertex split operations in any order. Consequently, the PM representation can be effectively encoded by permuting the vertex split operations in each group. Meanwhile, a Laplacian geometry predicator is desinged to predict each new verttex position using its neighbors.The correction is quantized and encoded using Huffman coding scheme.Experimental results show that the algorithm can obtain higer compression ratios than than the previous work.It is very suitable for progressive transmission of geometry models over Internet.
A progressive geometry compression scheme is presented in this paper. In this scheme, a mesh is represented as a base mesh followed by some groups of vertex split operations using an improved simplification method, in which each level of the mesh can be refined into the next level by carrying out a group of vertex split operations in any order. Consequently, the PM representation can be effectively encoded by permuting the vertex split operations in each group. Meanwhile, a Laplacian geometry predicator is desinged to predict each new verttex position using its neighbors.The correction is quantized and encoded using Huffman coding scheme.Experimental results show that the algorithm can obtain higer compression ratios than than the previous work.It is very suitable for progressive transmission of geometry models over Internet.
2002, 13(9):1813-1822.
Abstract:
In this paper, a Cartoon system is presented, which can generate a personalized Cartoon face from an input image. The system is designed for general users. After a realistic-looking Cartoon face automatically generated by this system, attractive Cartoon expressions and animation can be created with little user-interactions. The system consists of three main components, an image-based automatic Cartoon generator, a template-based Cartoon editor, and a speech-driven Cartoon animator. An example-based approach is taken by Cartoon generator to generate the Cartoon face while capturing an artist style.An inhomogenous non-parmetric sampling is employed to lwarn the atatistical relationship between the original image and the drawing.For editing,pre-designed expression templates are supplied by Cartoon editor editor.A real time lip-syncing algorithm is also developed to make Cartoon animation easily.The Cartoon and animation generated by this system have personal style.This is the main advantage of this system over others.
In this paper, a Cartoon system is presented, which can generate a personalized Cartoon face from an input image. The system is designed for general users. After a realistic-looking Cartoon face automatically generated by this system, attractive Cartoon expressions and animation can be created with little user-interactions. The system consists of three main components, an image-based automatic Cartoon generator, a template-based Cartoon editor, and a speech-driven Cartoon animator. An example-based approach is taken by Cartoon generator to generate the Cartoon face while capturing an artist style.An inhomogenous non-parmetric sampling is employed to lwarn the atatistical relationship between the original image and the drawing.For editing,pre-designed expression templates are supplied by Cartoon editor editor.A real time lip-syncing algorithm is also developed to make Cartoon animation easily.The Cartoon and animation generated by this system have personal style.This is the main advantage of this system over others.
2002, 13(9):1823-1829.
Abstract:
In this paper, an algorithm is presented to generate visual hulls of 3D objects. The algorithm fully utilizes the advantages of ADFs (adaptively sampled distance fields) in approximation precision and memory requirement. Different from the traditional voxel interpolation methods, the algorithm takes ADFs as the data structure to describe the visual hulls to simplify the interpolation process and improve the algorithm efficiency. Finally, the enhanced SurfaceNets algorithm is employed to triangulate ADFs in order to obtanin the topologically consistent models.The experimental results show that the algorithm can rapidly generate complex models with high precision.
In this paper, an algorithm is presented to generate visual hulls of 3D objects. The algorithm fully utilizes the advantages of ADFs (adaptively sampled distance fields) in approximation precision and memory requirement. Different from the traditional voxel interpolation methods, the algorithm takes ADFs as the data structure to describe the visual hulls to simplify the interpolation process and improve the algorithm efficiency. Finally, the enhanced SurfaceNets algorithm is employed to triangulate ADFs in order to obtanin the topologically consistent models.The experimental results show that the algorithm can rapidly generate complex models with high precision.
2002, 13(9):1830-1839.
Abstract:
To overcome the shortages of classic subdivision schemes, a kind of novel semi-stationary push subdivision schemes are proposed. Combined with the advantage of unified subdivision framework, semi-stationary control and push-back operator, the schemes in curve and surface case are given based on subdivision operator. And several limit properties are also discussed. These methods can generate a series of blending shapes between approximation and interpolation of the initial control mesh. In surface case, dire,direction tags are introduced to solve the fairness problem.The extensible schemes based on symbol representation are much useful in computer animation and industrial prototype design application.
To overcome the shortages of classic subdivision schemes, a kind of novel semi-stationary push subdivision schemes are proposed. Combined with the advantage of unified subdivision framework, semi-stationary control and push-back operator, the schemes in curve and surface case are given based on subdivision operator. And several limit properties are also discussed. These methods can generate a series of blending shapes between approximation and interpolation of the initial control mesh. In surface case, dire,direction tags are introduced to solve the fairness problem.The extensible schemes based on symbol representation are much useful in computer animation and industrial prototype design application.
2002, 13(9):1840-1845.
Abstract:
The intervisibility testing algorithm in the virtual environment that based on the LOS (line of sight) is researched on. After analyzing, the SO (sieve overlap) algorithm, which is more universal and efficient than other point to point intervisibility testing algorithm, is improved to fit more for the requirements of large-scale virtual environment and simulation. SO algorithm uses Bucket List and Singly Threaded Ternary Tree to manage and search the terrain polygon. The searching scale of Bucket List is reduced based on the AOI(area of interestiong).This makes the point to point intervisibility testing algorithm more real and efficient and gives the environmental infomation to the dynamic entity in the large scale virtual environment more efficiently.The space and time efficiency of the algorithm SO*and the SO is also compared.
The intervisibility testing algorithm in the virtual environment that based on the LOS (line of sight) is researched on. After analyzing, the SO (sieve overlap) algorithm, which is more universal and efficient than other point to point intervisibility testing algorithm, is improved to fit more for the requirements of large-scale virtual environment and simulation. SO algorithm uses Bucket List and Singly Threaded Ternary Tree to manage and search the terrain polygon. The searching scale of Bucket List is reduced based on the AOI(area of interestiong).This makes the point to point intervisibility testing algorithm more real and efficient and gives the environmental infomation to the dynamic entity in the large scale virtual environment more efficiently.The space and time efficiency of the algorithm SO*and the SO is also compared.
2002, 13(9):1846-1851.
Abstract:
A pen/speech multimodal interaction system for children is designed and implemented in this paper. The system contains an integration framework used to integrate the information input by children from pen and speech. Children can communicate with the computer in a natural way via the support of several pen/speech interaction techniques, which are defined by the system. Children can draw 3D scenes and creative animals through the use of pen and communicate with the scene and the entity via pen and speech detection.
A pen/speech multimodal interaction system for children is designed and implemented in this paper. The system contains an integration framework used to integrate the information input by children from pen and speech. Children can communicate with the computer in a natural way via the support of several pen/speech interaction techniques, which are defined by the system. Children can draw 3D scenes and creative animals through the use of pen and communicate with the scene and the entity via pen and speech detection.
2002, 13(9):1852-1857.
Abstract:
An approach is proposed to recover material of a homogeneous object in a general environment from a single high dynamic range image. There is no limitation on the shape and illumination condition of the object. In a general environment, acquire a high dynamic range image for an object and one or a few high dynamic range environment maps as illumination of the object. Then the simulated annealing algorithm is employed to solve the inverse rendering problem. In the course of optimization, image-based lighting and ray tracing techiques are used,and inter-reflection is calculated.Finally,oparameter valuse for the reflection model are obtained.Combined with the image-based modeling techniques,a realistic model can be created form images of a real object.
An approach is proposed to recover material of a homogeneous object in a general environment from a single high dynamic range image. There is no limitation on the shape and illumination condition of the object. In a general environment, acquire a high dynamic range image for an object and one or a few high dynamic range environment maps as illumination of the object. Then the simulated annealing algorithm is employed to solve the inverse rendering problem. In the course of optimization, image-based lighting and ray tracing techiques are used,and inter-reflection is calculated.Finally,oparameter valuse for the reflection model are obtained.Combined with the image-based modeling techniques,a realistic model can be created form images of a real object.
2002, 13(9):1858-1865.
Abstract:
Level Set method is a power tool for tracking the evolution of fronts propagating with curvature dependent speed. Since its introduction, Level Set method has been used in a wide collection of problems such as medical image processing, the simulation of natural phenomenon and computer vision. In practical applications, two of the most important algorithms are how to smooth the grid value and track the fronts contour after some time steps. In this paper, a simple method is introduced to smooth the value of Level Set function.It uses only intra-interpolation to clear out all of the single points and soms of the ambiguous points.Use the contor line tracking method introduced in this paper,people can get the contour lies of all of the curves in a plane,even if there exists some redundant points.The experimental results show that this method is simple and useful,and can be used to wide fields concerning with fronts propagating.
Level Set method is a power tool for tracking the evolution of fronts propagating with curvature dependent speed. Since its introduction, Level Set method has been used in a wide collection of problems such as medical image processing, the simulation of natural phenomenon and computer vision. In practical applications, two of the most important algorithms are how to smooth the grid value and track the fronts contour after some time steps. In this paper, a simple method is introduced to smooth the value of Level Set function.It uses only intra-interpolation to clear out all of the single points and soms of the ambiguous points.Use the contor line tracking method introduced in this paper,people can get the contour lies of all of the curves in a plane,even if there exists some redundant points.The experimental results show that this method is simple and useful,and can be used to wide fields concerning with fronts propagating.
2002, 13(9):1866-1872.
Abstract:
This paper focuses on the image segmentation, which is one of the key problems in medical image processing. A medical image segmentation method is proposed based on the combination of fast marching method and watershed transformation. First, the original image is smoothed by using nonlinear diffusion filter. Then the smoothed image is over-segmented by the watershed algorithm. Finally, the image is segmented automatically by using the modified fast marching method. Moreover, the speed function is defined based on the staristiical similarity degree of the regions.Experimental results show that the algorithm can obtanin segmentation result of medical image fast and accurately.
This paper focuses on the image segmentation, which is one of the key problems in medical image processing. A medical image segmentation method is proposed based on the combination of fast marching method and watershed transformation. First, the original image is smoothed by using nonlinear diffusion filter. Then the smoothed image is over-segmented by the watershed algorithm. Finally, the image is segmented automatically by using the modified fast marching method. Moreover, the speed function is defined based on the staristiical similarity degree of the regions.Experimental results show that the algorithm can obtanin segmentation result of medical image fast and accurately.
2002, 13(9):1873-1880.
Abstract:
The existing 3D reconstruction methods cannot be effectively applied in architecture domain. A new method that is based on the architectural cartography criterion, techniques of AI and graphics recognition and understanding, is presented for automatic recognition and reconstruction of architectural structures by interpreting three-view drawings. In this method, automatic recognition of the architectural components?contours, integration of semantic information interpreted from symbols and notes etc., and analyzing topology relation of adjacent components are applied to reconstruct the whole building rapidly and effectually.Experimental results show that the method is efficient and accurate for automatic reconstruction of buildings composed of large number of components from their structure drawings with little user correction.
The existing 3D reconstruction methods cannot be effectively applied in architecture domain. A new method that is based on the architectural cartography criterion, techniques of AI and graphics recognition and understanding, is presented for automatic recognition and reconstruction of architectural structures by interpreting three-view drawings. In this method, automatic recognition of the architectural components?contours, integration of semantic information interpreted from symbols and notes etc., and analyzing topology relation of adjacent components are applied to reconstruct the whole building rapidly and effectually.Experimental results show that the method is efficient and accurate for automatic reconstruction of buildings composed of large number of components from their structure drawings with little user correction.
2002, 13(9):1881-1886.
Abstract:
A computer model capable of generating stylized light rain and heavy rain for cartoon animation is presented. How to analyze and extract the static and dynamic structures associated with trajectories of raindrops from hand-drawn cartoon series is shown at first. Based upon those structures, how to generate their skeletons and control dynamic behaviors of those skeletons is also shown. The single pass is used in the light rain model and the multiple passes are used in the heavy rain model, and in the later case the effects is enhanced by animating a cycle of drops hitting the ground.Due to the stochastic control mechanism used in the model,the resultant effects avoid the mechanical look that may cause by using repotitive cycles in hand drawn animation.To suggest mood,animators have to drfferent series with different timing and orentation of raindrops,while by varying a few parameters. the model can achieve the same results great ease.The method is also able to generate both 2D and 3D cartoon raindrops for animation.
A computer model capable of generating stylized light rain and heavy rain for cartoon animation is presented. How to analyze and extract the static and dynamic structures associated with trajectories of raindrops from hand-drawn cartoon series is shown at first. Based upon those structures, how to generate their skeletons and control dynamic behaviors of those skeletons is also shown. The single pass is used in the light rain model and the multiple passes are used in the heavy rain model, and in the later case the effects is enhanced by animating a cycle of drops hitting the ground.Due to the stochastic control mechanism used in the model,the resultant effects avoid the mechanical look that may cause by using repotitive cycles in hand drawn animation.To suggest mood,animators have to drfferent series with different timing and orentation of raindrops,while by varying a few parameters. the model can achieve the same results great ease.The method is also able to generate both 2D and 3D cartoon raindrops for animation.
2002, 13(9):1887-1892.
Abstract:
The colors and the opacity of voxels in transfer function should be assigned in order to display hide interfaces (the interface of inner different mediums) in objects by direct volume rendering based on the general volume light model. Although the inner structure of objects is seen, it is not clear to see inner hide interfaces from the surface based on this model. One reason is that the general volume light model does not have the attribute of select transparency. The particles in 3D space are not penetrated by visible lights with one wavelength and absorb visible lights with another different wavlength.They can only absorb all kinds of visible lisible light in the same extent. Another reason is that it is short of surface information.A light model with the attribute of select transparency is used in the new algorithm,and the surface scatter which has nothing to do with the line of sight and the position of light source is put up into it.Meanwhile,the non-photorealistic rendering techniques are used to advance effects of inner hide interfaces.The hide interfaces and details are clearly displayed based on the new light model.
The colors and the opacity of voxels in transfer function should be assigned in order to display hide interfaces (the interface of inner different mediums) in objects by direct volume rendering based on the general volume light model. Although the inner structure of objects is seen, it is not clear to see inner hide interfaces from the surface based on this model. One reason is that the general volume light model does not have the attribute of select transparency. The particles in 3D space are not penetrated by visible lights with one wavelength and absorb visible lights with another different wavlength.They can only absorb all kinds of visible lisible light in the same extent. Another reason is that it is short of surface information.A light model with the attribute of select transparency is used in the new algorithm,and the surface scatter which has nothing to do with the line of sight and the position of light source is put up into it.Meanwhile,the non-photorealistic rendering techniques are used to advance effects of inner hide interfaces.The hide interfaces and details are clearly displayed based on the new light model.
2002, 13(9):1893-1898.
Abstract:
An adaptively deformable model for web-based virtual surgery is proposed. In this model, external forces propagate on layer-by-layer basis into soft tissues and thereby leading to changes in shape. By controlling the penetration depth of external forces, deformation is restricted to occur only in localized regions, and optimization between computational complexity and accuracy is achieved. This technique avoids laborious formulation of stiffness matrix in conventional mass-spring models. Experimental result show that the model is suitable for modeling materials of various mechanical properties.It can also be used for multi-user collaborative work in virtual enbironments and integrated with multiple degree-of-freedom haptic devices.
An adaptively deformable model for web-based virtual surgery is proposed. In this model, external forces propagate on layer-by-layer basis into soft tissues and thereby leading to changes in shape. By controlling the penetration depth of external forces, deformation is restricted to occur only in localized regions, and optimization between computational complexity and accuracy is achieved. This technique avoids laborious formulation of stiffness matrix in conventional mass-spring models. Experimental result show that the model is suitable for modeling materials of various mechanical properties.It can also be used for multi-user collaborative work in virtual enbironments and integrated with multiple degree-of-freedom haptic devices.
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Copyright: Institute of Software, Chinese Academy of Sciences Beijing ICP No. 05046678-4
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Copyright: Institute of Software, Chinese Academy of Sciences Beijing ICP No. 05046678-4
Address：4# South Fourth Street, Zhong Guan Cun, Beijing 100190,Postal Code：100190
Phone：010-62562563 Fax：010-62562533 Email：jos@iscas.ac.cn
Technical Support：Beijing Qinyun Technology Development Co., Ltd.
