Ray casting algorithm can obtain a better quality image in volume rendering, however, it exists some problems, such as powerful computing capacity and slow rendering speed. How to improve the re-sampled speed is a key...Ray casting algorithm can obtain a better quality image in volume rendering, however, it exists some problems, such as powerful computing capacity and slow rendering speed. How to improve the re-sampled speed is a key to speed up the ray casting algorithm. An algorithm is introduced to reduce matrix computation by matrix transformation characteristics of re-sampling points in a two coordinate system. The projection of 3-D datasets on image plane is adopted to reduce the number of rays. Utilizing boundary box technique avoids the sampling in empty voxel. By extending the Bresenham algorithm to three dimensions, each re-sampling point is calculated. Experimental results show that a two to three-fold improvement in rendering speed using the optimized algorithm, and the similar image quality to traditional algorithm can be achieved. The optimized algorithm can produce the required quality images, thus reducing the total operations and speeding up the volume rendering.展开更多
Aiming to deal with the difficult issues of terrain data model simplification and crack disposal,the paper proposed an improved level of detail(LOD)terrain rendering algorithm,in which a variation coefficient of eleva...Aiming to deal with the difficult issues of terrain data model simplification and crack disposal,the paper proposed an improved level of detail(LOD)terrain rendering algorithm,in which a variation coefficient of elevation is introduced to express the undulation of topography.Then the coefficient is used to construct a node evaluation function in the terrain data model simplification step.Furthermore,an edge reduction strategy is combined with the improved restrictive quadtree segmentation to handle the crack problem.The experiment results demonstrated that the proposed method can reduce the amount of rendering triangles and enhance the rendering speed on the premise of ensuring the rendering effect compared with a traditional LOD algorithm.展开更多
To improve the sense of reality on perception, an improved algorithm of 3D shape haptic rendering is put forward based on a finger mounted vibrotactile device. The principle is that the interactive information and the...To improve the sense of reality on perception, an improved algorithm of 3D shape haptic rendering is put forward based on a finger mounted vibrotactile device. The principle is that the interactive information and the shape information are conveyed to users when they touch virtual objects at mobile terminals by attaching the vibrotactile feedback on a fingertip. The extraction of shape characteristics, the interactive information and the mapping of shape in formation of vibration stimulation are key parts of the proposed algorithm to realize the real tactile rendering. The contact status of the interaction process, the height information and local gradient of the touch point are regarded as shape information and used to control the vibration intension, rhythm and distribution of the vibrators. With different contact status and shape information, the vibration pattern can be adjusted in time to imitate the outlines of virtual objects. Finally, the effectiveness of the algorithm is verified by shape perception experiments. The results show that the improved algorithm is effective for 3D shape haptic rendering.展开更多
Direct isosurface volume rendering is the most prominent modern method for medical data visualization.It is based on finding intersection points between the rays corresponding to pixels on the screen and isosurface. T...Direct isosurface volume rendering is the most prominent modern method for medical data visualization.It is based on finding intersection points between the rays corresponding to pixels on the screen and isosurface. This article describes a two-pass algorithm for accelerating the method on the graphic processing unit(GPU). On the first pass, the intersections with the isosurface are found only for a small number of rays, which is done by rendering into a lower-resolution texture. On the second pass, the obtained information is used to efficiently calculate the intersection points of all the other. The number of rays to use during the first pass is determined by using an adaptive algorithm, which runs on the central processing unit(CPU) in parallel with the second pass of the rendering. The proposed approach allows to significantly speed up isosurface visualization without quality loss. Experiments show acceleration up to 10 times in comparison with a common ray casting method implemented on GPU. To the authors’ knowledge, this is the fastest approach for ray casting which does not require any preprocessing and could be run on common GPUs.展开更多
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 compressio...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.展开更多
The visual fidelity of bleeding simulation in a surgical simulator is critical since it will affect not only the degree of visual realism,but also the user’s medical judgment and treatment in real-life settings.The c...The visual fidelity of bleeding simulation in a surgical simulator is critical since it will affect not only the degree of visual realism,but also the user’s medical judgment and treatment in real-life settings.The conventional marching cubes surface rendering algorithm provides excellent visual effect in rendering gushing blood,however,it is insufficient for blood flow,which is very common in surgical procedures,since in this case the rendered surface and depth textures of blood are rough.In this paper,we propose a new method called the mixed depth rendering for rendering blood flow in surgical simulation.A smooth height field is created to minimize the height difference between neighboring particles on the bleeding surface.The color and transparency of each bleeding area are determined by the number of bleeding particles,which is consistent with the real visual effect.In addition,there is no much extra computational cost.The rendering of blood flow in a variety of surgical scenarios shows that visual feedback is much improved.The proposed mixed depth rendering method is also used in a neurosurgery simulator that we developed.展开更多
森林的实时渲染及光照是视景系统中的一个难题.基于图像的渲染方法(IBR)由于渲染速度与模型复杂度无关,被广泛应用于场景重建.基于光流场(Light Field Rendering)的IBR技术,提出一种迭代投射算法来进行外形重建,实现了具有实时光影特征...森林的实时渲染及光照是视景系统中的一个难题.基于图像的渲染方法(IBR)由于渲染速度与模型复杂度无关,被广泛应用于场景重建.基于光流场(Light Field Rendering)的IBR技术,提出一种迭代投射算法来进行外形重建,实现了具有实时光影特征的森林效果.实验表明该算法结合了传统迭代、投射算法各自的优点,在质量和效率方面取得了平衡.展开更多
This paper introduces the techniques of direct volume rendering in VTK and discusses ray-casting--the most popular technique of direct volume rendering. The visualizations for medical volumetric data by three function...This paper introduces the techniques of direct volume rendering in VTK and discusses ray-casting--the most popular technique of direct volume rendering. The visualizations for medical volumetric data by three functions of raycasting are offered. Visualization effects prove that VTK is easy to get satisfied resuits with good quality in short time.展开更多
文摘Ray casting algorithm can obtain a better quality image in volume rendering, however, it exists some problems, such as powerful computing capacity and slow rendering speed. How to improve the re-sampled speed is a key to speed up the ray casting algorithm. An algorithm is introduced to reduce matrix computation by matrix transformation characteristics of re-sampling points in a two coordinate system. The projection of 3-D datasets on image plane is adopted to reduce the number of rays. Utilizing boundary box technique avoids the sampling in empty voxel. By extending the Bresenham algorithm to three dimensions, each re-sampling point is calculated. Experimental results show that a two to three-fold improvement in rendering speed using the optimized algorithm, and the similar image quality to traditional algorithm can be achieved. The optimized algorithm can produce the required quality images, thus reducing the total operations and speeding up the volume rendering.
基金Supported by the National Natural Science Foundation of China(61363075)the National High Technology Research and Development Program of China(863 Program)(2012AA12A308)the Yue Qi Young Scholars Program of China University of Mining&Technology,Beijing(800015Z1117)
文摘Aiming to deal with the difficult issues of terrain data model simplification and crack disposal,the paper proposed an improved level of detail(LOD)terrain rendering algorithm,in which a variation coefficient of elevation is introduced to express the undulation of topography.Then the coefficient is used to construct a node evaluation function in the terrain data model simplification step.Furthermore,an edge reduction strategy is combined with the improved restrictive quadtree segmentation to handle the crack problem.The experiment results demonstrated that the proposed method can reduce the amount of rendering triangles and enhance the rendering speed on the premise of ensuring the rendering effect compared with a traditional LOD algorithm.
基金The National Natural Science Foundation of China(No.61473088)Six Talent Peaks Projects in Jiangsu Province
文摘To improve the sense of reality on perception, an improved algorithm of 3D shape haptic rendering is put forward based on a finger mounted vibrotactile device. The principle is that the interactive information and the shape information are conveyed to users when they touch virtual objects at mobile terminals by attaching the vibrotactile feedback on a fingertip. The extraction of shape characteristics, the interactive information and the mapping of shape in formation of vibration stimulation are key parts of the proposed algorithm to realize the real tactile rendering. The contact status of the interaction process, the height information and local gradient of the touch point are regarded as shape information and used to control the vibration intension, rhythm and distribution of the vibrators. With different contact status and shape information, the vibration pattern can be adjusted in time to imitate the outlines of virtual objects. Finally, the effectiveness of the algorithm is verified by shape perception experiments. The results show that the improved algorithm is effective for 3D shape haptic rendering.
文摘Direct isosurface volume rendering is the most prominent modern method for medical data visualization.It is based on finding intersection points between the rays corresponding to pixels on the screen and isosurface. This article describes a two-pass algorithm for accelerating the method on the graphic processing unit(GPU). On the first pass, the intersections with the isosurface are found only for a small number of rays, which is done by rendering into a lower-resolution texture. On the second pass, the obtained information is used to efficiently calculate the intersection points of all the other. The number of rays to use during the first pass is determined by using an adaptive algorithm, which runs on the central processing unit(CPU) in parallel with the second pass of the rendering. The proposed approach allows to significantly speed up isosurface visualization without quality loss. Experiments show acceleration up to 10 times in comparison with a common ray casting method implemented on GPU. To the authors’ knowledge, this is the fastest approach for ray casting which does not require any preprocessing and could be run on common GPUs.
基金Project supported by the National Basic Research Program (973) of China (No. 2002CB312105), the National Natural Science Founda-tion of China (No. 60573074), the Natural Science Foundation of Shanxi Province, China (No. 20041040), Shanxi Foundation of Tackling Key Problem in Science and Technology (No. 051129), and Key NSFC Project of "Digital Olympic Museum" (No. 60533080), China
文摘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.
基金supported the National Science Foundation of China(61773051,61761166011,51705016)Beijing Natural Science Foundation(4172048)the Fundamental Research Funds for the Central Universities(2017JBZ003)
文摘The visual fidelity of bleeding simulation in a surgical simulator is critical since it will affect not only the degree of visual realism,but also the user’s medical judgment and treatment in real-life settings.The conventional marching cubes surface rendering algorithm provides excellent visual effect in rendering gushing blood,however,it is insufficient for blood flow,which is very common in surgical procedures,since in this case the rendered surface and depth textures of blood are rough.In this paper,we propose a new method called the mixed depth rendering for rendering blood flow in surgical simulation.A smooth height field is created to minimize the height difference between neighboring particles on the bleeding surface.The color and transparency of each bleeding area are determined by the number of bleeding particles,which is consistent with the real visual effect.In addition,there is no much extra computational cost.The rendering of blood flow in a variety of surgical scenarios shows that visual feedback is much improved.The proposed mixed depth rendering method is also used in a neurosurgery simulator that we developed.
文摘森林的实时渲染及光照是视景系统中的一个难题.基于图像的渲染方法(IBR)由于渲染速度与模型复杂度无关,被广泛应用于场景重建.基于光流场(Light Field Rendering)的IBR技术,提出一种迭代投射算法来进行外形重建,实现了具有实时光影特征的森林效果.实验表明该算法结合了传统迭代、投射算法各自的优点,在质量和效率方面取得了平衡.
基金The author gratefully acknowledges the support of Youth for NWPUTeachers Scientific and Technological Innovation Foundation (5210102-0800-M016206)This work is supported by a grant for PH.D Site from Chinese Educational Department (20040699015)The authors are thankful to Guiqing He, PhD and Chongyang Hao, professor for many help and interesting discussions.
文摘This paper introduces the techniques of direct volume rendering in VTK and discusses ray-casting--the most popular technique of direct volume rendering. The visualizations for medical volumetric data by three functions of raycasting are offered. Visualization effects prove that VTK is easy to get satisfied resuits with good quality in short time.
