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1.
唐勇  霍丽娜  吕梦雅 《计算机工程》2009,35(18):272-274
针对现有头发模型缺乏柔性的问题,提出一种改进的基于超螺旋模型的头发建模与仿真方法,将导引发丝构造成具有有限自由度的分段螺旋体,运用拉格朗日力学对发丝运动进行计算。通过改进卷发曲率和捻度的计算方法,并采用自适应控制结构对头发进行重组和细分,提高模拟过程的准确性和稳定性。实验结果证明,该方法可以获得较为逼真的动态模拟头发的效果。  相似文献   

2.
提出了一种结合几何动力学的卡通头发生成方法。它包括头发的几何建模和动力学模拟两个部分。在几何建模阶段:用户导入一个头部模型,交互指定头发生长区域控制点和头发模型中心控制点,系统自动生成卡通头发的几何模型。在动力学模拟阶段:引入基于网格的逆向动力学实现卡通头发运动。实验结果表明:系统通过简单的用户交互能够制作出令人满意的卡通头发。  相似文献   

3.
针对基于弹性杆理论的超螺旋模型中对动力学方程的求解影响头发模拟实时性的问题,采用Cosserat弹性杆理论对头发建模,引入角速度变量,并加入头发运动平衡的固有约束,得到改进的拉格朗日动力学运动方程;然后,将头发单体离散化,用角速度和四元数作为状态变量简化动力学方程,用半显式的欧拉方程加速方程的执行,大大降低了系统的运行时间,提高了模拟的速度,在满足实时性要求的同时提高了头发模拟的真实度。  相似文献   

4.
机械加工过程仿真中运动物体的碰撞检测   总被引:1,自引:1,他引:0  
本文提出了一种表达实体的八叉树层次球状模型和基于这种模型的运动物体之间的碰撞检测算法。机械加工过程的图形仿真对NC程序的检验是十分有用的,因为编程者或加工操作者能够很方便地看到加工的效果。由于在加工过程中,刀具和工件等都是运动物体,而要从图形上直接目测运动物体之间的碰撞情况是十分困难的。所以,本文提出了一种表示运动物体的模型及相应的碰撞检测算法。一个物体可用一个八叉树层次球模型来表示,其运动可以用节点的外接球的球心的运动来表示,它是时间的函数。通过求解满足碰撞条件的方程,我们可以得到两运动物体碰撞时间和位置。本文最后对碰撞检测算法的特性进行了分析。  相似文献   

5.
在现代的一些虚拟现实系统中,如模拟人体模型、游戏以及电影特技中需要对头发的真实感进行建模。虚拟现实的关键技术之一是对显示对象进行建模。因此,为解决由于头发数量庞大和其纤细的特性而使得头发图像生成过程缓慢复杂的问题,研究其相关技术具有重要价值。头发模拟的方法主要有:直接模拟、体积纹理模型、聚簇发束模型和宽松连接的粒子系统模型等。该文在现有的头发模拟方法分析的基础上,提出了一种基于粒子系统的头发模拟设计方法,从而在时间和计算开销上解决已有方法的不足。  相似文献   

6.
运用模拟头发运动的系统计算头发阴影的阴影生成算法和一个通过每一串头发来模拟光线散射的发射模型,就可以创建出极其真实的头发影像。渲染结果表明,利用以上方法可以渲染出极其逼真的头发。  相似文献   

7.
针对头发的不可伸展性和数量过大造成的头发仿真时性能低效、真实感不高问题,提出一种新的头发动态仿真方法。该方法首先利用弹簧模型对单根头发进行建模,然后采用DFTL(Dynamic Follow The Leader)算法进行变形计算,并基于FTL(Static Follow The Leader)算法对头发进行快速插值,最后运用Deep Opacity Mapping技术对头发进行渲染,增强虚拟人头发的真实感。同时,对头发与头部模型、头发与头发进行碰撞检测与响应。实验结果表明,该方法生成的头发逼真自然,而且在大量渲染时保持了较高的稳定性。  相似文献   

8.
文章介绍了头发悬臂梁弯曲模型,提出用面集合仿真真实的头发,生成具有光照效果的图象。同时,提出了以椭球为头壳生成头发模型后,将其移植到实际存在的头部模型上的方法,以及头发与头部的碰撞检测手段,从而获得长有头发的完整的头部图象。  相似文献   

9.
基于Open Inventor的虚拟驾驶仿真系统   总被引:1,自引:0,他引:1  
基于虚拟现实技术,以3ds MAX为建模软件,Open Inventor为开发平台,通过面向对象的编程方法设计了虚拟驾驶仿真系统,介绍了三维模型的导入、层次细节技术、碰撞检测、运动相机的控制与渲染等关键技术.通过实验表明,本系统真实地模拟了汽车在驾驶过程中起步、换挡、加减速、转向、制动等行驶工况,并实时地通过碰撞检测算法来判断虚拟车辆模型与虚拟场景之间的碰撞.  相似文献   

10.
碰撞检测是虚拟制造中重要的课题之一,文章针对Java3D对三维物体碰撞检测支持的局限性,通过扩展Java3D的功能,构造了一种碰撞检测系统,采用了二叉树层次球模型来表示实体,对运动物体间进行碰撞检测,满足了可靠性和时间的连续性,较好地适应复杂环境的碰撞检测的需求。  相似文献   

11.
We present an efficient and accurate algorithm for self‐collision detection in deformable models. Our approach can perform discrete and continuous collision queries on triangulated meshes. We present a simple and linear time algorithm to perform the normal cone test using the unprojected 3D vertices, which reduces to a sequence point‐plane classification tests. Moreover, we present a hierarchical traversal scheme that can significantly reduce the number of normal cone tests and the memory overhead using front‐based normal cone culling. The overall algorithm can reliably detect all (self) collisions in models composed of hundreds of thousands of triangles. We observe considerable performance improvement over prior continuous collision detection algorithms.  相似文献   

12.
为对包含日光温室的农业场景进行实时、逼真的绘制,采用基于视点的连续细节层次(LOD)来减少实际需要绘制的网格数据量,并基于包围盒技术实现了视点的碰撞检测,同时使用可见性剔除算法来加速场景渲染速度。在渲染温室内植物时,通过几何变换实现了大规模植物群体的快速构建,并在场景中使用阴影体算法来渲染阴影,生成了具有真实感的大规模温室农业场景。模拟结果表明该方法能有效地减少渲染的面元数目,大大提高了绘制速率,场景有较高的真实感,能够满足交互式实时漫游的要求。  相似文献   

13.
We present an improved uniform subdivision based discrete and continuous collision detection approach for deformable objects consisting of triangle meshes without any assumption about triangle size. A previously proposed technique using control bits can effectively eliminate redundant object pairs appearing in multiple cells, but this scheme requires the grid cell size adapted to the largest object, and efficiency tends to be severely impaired when object size varies strongly. In this paper, we discuss an approach that virtually subdivides large triangles into a number of child triangles to enable the use of a smaller, better suited cell size, resulting in a considerable decrease in the number of collision tests in the broad phase, with a corresponding reduced memory requirement. The virtual subdivision is used only for the purpose of collision detection and is recomputed each frame, with the original mesh retained for collision response and physical simulation. Our method exploits the benefits of GPU architecture to accelerate the computationally intensive task for improved performance. The results show that the method provides speedups by comparing performance with existing methods.  相似文献   

14.
This paper presents a new, simple and practical algorithm to avoid artifacts when switching between discrete levels of detail (LOD) by smoothly blending LOD representations in image space. We analyse the alternatives of conventional alpha‐blending and so‐called late‐switching (the switching of LODs ‘far enough’ from the eye‐point), widely thought to solve the LOD switching discontinuity problem, and conclude that they either do not work in practice, or defeat the concept of LODs. In contrast we show that our algorithm produces visually pleasing blends for static and animated discrete LODs, for discrete LODs with different types of LOD representations (e.g. billboards and meshes) and even to some extent totally different objects with similar spatial extent, with a very small runtime overhead.  相似文献   

15.
We present novel parallel algorithms for collision detection and separation distance computation for rigid and deformable models that exploit the computational capabilities of many‐core GPUs. Our approach uses thread and data parallelism to perform fast hierarchy construction, updating, and traversal using tight‐fitting bounding volumes such as oriented bounding boxes (OBB) and rectangular swept spheres (RSS). We also describe efficient algorithms to compute a linear bounding volume hierarchy (LBVH) and update them using refitting methods. Moreover, we show that tight‐fitting bounding volume hierarchies offer improved performance on GPU‐like throughput architectures. We use our algorithms to perform discrete and continuous collision detection including self‐collisions, as well as separation distance computation between non‐overlapping models. In practice, our approach (gProximity) can perform these queries in a few milliseconds on a PC with NVIDIA GTX 285 card on models composed of tens or hundreds of thousands of triangles used in cloth simulation, surgical simulation, virtual prototyping and N‐body simulation. Moreover, we observe more than an order of magnitude performance improvement over prior GPU‐based algorithms.  相似文献   

16.
This is an extended version of the paper presented at the 4th International Workshop NFMCP 2015 held in conjunction with ECML PKDD 2015. The initial version has been published in NFMCP 2015 conference proceedings as part of Springer Series. This paper presents a novel approach to financial times series (FTS) prediction by mapping hourly foreign exchange data to string representations and deriving simple trading strategies from them. To measure the degree of similarity in these market strings we apply familiar string kernels, bag of words and n-grams, whilst also introducing a new kernel, time-decay n-grams, that captures the temporal nature of FTS. In the process we propose a sequential Parzen windows algorithm based on discrete representations where trading decisions for each string are learned in an online manner and are thus subject to temporal fluctuations. We evaluate the strength of a number of representations using both the string version and its continuous counterpart, whilst also comparing the performance of different learning algorithms on these representations, namely support vector machines, Parzen windows and Fisher discriminant analysis. Our extensive experiments show that the simple string representation coupled with the sequential Parzen windows approach is capable of outperforming other more exotic approaches, supporting the idea that when it comes to working in high noise environments often the simplest approach is the most effective.  相似文献   

17.
Collision detection is fundamental in achievingnatural dynamics in virtual environments, but current algorithms are too slow, causing a major bottleneck in processing and hindering the building of interactive simulation environments. This paper provides an overview of the collision detection problem and current attempted solutions. A voxel-based approach to rigid-body collision detection is presented, with its potential high performance explained.Voxel collision detection takes place on a pair-wise basis, involving two additional representations of a polygonal object, a Voxmap and a Point Shell. These are constructed in a pre-processing step and allow fast collision detection through a simple look-up reference of points into voxels. Collision performance depends upon the number of points in the shell, and can trade accuracy for speed. A range ofpruning techniques, needed to cut down the number of objects undergoing collision testing, are reviewed and implemented. These allow most effective use of the voxel collision detection algorithm in multi-body simulations, such as virtual environments.Performance evaluations demonstrate the voxel collision detection algorithm's ability to achieve interactive rates (above 20 Hz) for both high precision pair-wise collision tests, and for large numbers of objects in multi-body environments. The voxel collision detection algorithm is suitable for parallel, hardware implementation. This provides the potential for great enhancements to already extremely high performance, rendering the voxel-based approach to collision detection all the more promising.  相似文献   

18.
Two articulated robots working in a shared workspace can be programmed by planning the tip trajectory of each robot independently. To account for collision avoidance between links, a real-time velocity alteration strategy based on fast and accurate collision detection is proposed in this paper to determine the step of next motion of slave (low priority) robot for collision-free trajectory planning of two robots with priorities. The effectiveness of the method depends largely on a newly developed method of accurate estimate of distance between links. By using the enclosing and enclosed ellipsoids representations of polyhedral models of links of robots, the minimum distance estimate and collision detection between the links can be performed more efficiently and accurately. The proposed strategy is implemented in an environment where the geometric paths of robots are pre-planned and the preprogrammed velocities are piecewise constant but adjustable. Under the control of the proposed strategy, the master robot always moves at a constant speed. The slave robot moves at the selected velocity, selected by a tradeoff between collision trend index and velocity reduction in one collision checking time, to keep moving as far as possible and as fast as possible while avoid possible collisions along the path. The collision trend index is a fusion of distance and relative velocity between links of two robots to reflect the possibility of collision at present and in the future. Graphic simulations of two PUMA560 robot arms working in common workspace but with independent goals are conducted. Simulations demonstrate the collision avoidance capability of the proposed approach as compared to the approach based on bounding volumes. It shows that advantage of our approach is less number of speed alterations required to react to potential collisions.  相似文献   

19.
We present a novel hierarchical grid based method for fast collision detection (CD) for deformable models on GPU architecture. A two‐level grid is employed to accommodate the non‐uniform distribution of practical scene geometry. A bottom‐to‐top method is implemented to assign the triangles into the hierarchical grid without any iteration while a deferred scheme is introduced to efficiently update the data structure. To address the issue of load balancing, which greatly influences the performance in SIMD parallelism, a propagation scheme which utilizes a parallel scan and a segmented scan is presented, distributing workloads evenly across all concurrent threads. The proposed method supports both discrete collision detection (DCD) and continuous collision detection (CCD) with self‐collision. Some typical benchmarks are tested to verify the effectiveness of our method. The results highlight our speedups over prior algorithms on different commodity GPUs.  相似文献   

20.
We present a new hybrid CPU/GPU collision detection technique for rigid and deformable objects based on spatial subdivision. Our approach efficiently exploits the massive computational capabilities of modern CPUs and GPUs commonly found in off‐the‐shelf computer systems. The algorithm is specifically tailored to be highly scalable on both the CPU and the GPU sides. We can compute discrete and continuous external and self‐collisions of non‐penetrating rigid and deformable objects consisting of many tens of thousands of triangles in a few milliseconds on a modern PC. Our approach is orders of magnitude faster than earlier CPU‐based approaches and up to twice as fast as the most recent GPU‐based techniques.  相似文献   

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