共查询到20条相似文献,搜索用时 93 毫秒
1.
2.
提出一种求解对象族模型的新的几何求解方法。提出两种新类型的组,即可伸缩组和可放射组。在刚性组或非刚性组系统中穷举地使用重写规则的较小的集合,一直到没有可用的重写规则为止,最后的组的集合就表示系统的求解策略。提出并实现一种增量算法,以及在这种新的求解方法中的解选择方法,这些方法都可以高效地找到问题的解,并减少解的个数。 相似文献
3.
4.
在模型制造领域,对于拓扑约束的求解是一个比较新的课题,以往的研究一直局限在拓扑优化方面。而且对其应用也仅限于模型的定义方面,在模型的声明与约束求解方面却没有得到应用。文章提出一种基于细胞元模型拓扑约束求解方法,通过该方法可以确定模型拓扑声明的关系,文章假设一个模型是由一个或多个细胞元组成的,并且能够用这些细胞元的组合来表示,对模型进行拓扑约束求解就是用来确定细胞模型中的每个细胞元是否是全约束的。要做到这点,文章将每个细胞元用一个布尔变量表示,把拓扑约束问题映射成为布尔可满足性问题。再对新的问题进行求解,从而解决了模型的拓扑约束求解问题。 相似文献
5.
6.
7.
本文研究了菱形对象族的鲁棒镇定问题。当控制器取为分子,分母为仅有奇次项的或仅有偶次荐的多项式的真有理分式时,证明了该控制器鲁棒镇定菱形对象族的充分必要条件为该控制器同时镇定三十二个顶点对象。当上述控制器的分子,分母限于正负交错系数的仅有奇次项的或仅有偶次项的多项式时,该控制器鲁棒镇定菱形对象族所需同时镇定的顶点对象最多为十六个,所进结果与对象族的阶次无关。 相似文献
8.
空间对象及其拓扑关系 总被引:2,自引:0,他引:2
论文首先讨论了传统的地理信息系统中空间对象的空间数据模型,提出了面向对象的层次矢量数据模型。然后定性地分析了空间对象点与点、点与线和点与区域之间的拓扑关系,并给出了一种形式化表达空间对象成分拓扑关系的模型。最后,将这种模型与空间对象之间的拓扑关系结合起来,使其可以方便地处理地理信息系统中的对象间的拓扑关系。 相似文献
9.
在数字地球、数字城市、地理信息系统等涉及地理数据等许多应用中,三维空间对象的拓扑关系的研究是一个十分重要的问题;弄清三维空间对象的拓扑关系,对于三维空间对象的操作以及操作的算法研究至关重要。由于三维空间对象的复杂性,它们之间拓扑关系的判定大多只是从简单的概念来进行判断,还没有从理论上全面地给定它的判定准则。该文试图在三维空间中,详细地研究空间对象之间拓扑关系成立的条件与结论,利用这些规则,可以全面地得到三维空间对象之间可能存在的所有拓扑关系。 相似文献
10.
线与体是3维空间中两类重要的空间对象,对其之间的拓扑关系进行研究在地矿开采、交通运输等很多领域都有非常重要的应用价值。为了准确高效地对3维空间线与体,特别是复杂对象间的拓扑关系进行分析,首先定义了一类基本空间对象,同时用9交模型来表达空间对象之间的拓扑关系;然后利用线与体之间的9条否定规则推导出基本线与体之间可能存在的11种拓扑关系,再利用复合推导的方法来得到复合线对象与体之间的19种拓扑关系;最后得出了用于推导分析复杂线与体之间拓扑关系的算法。经过详细分析与讨论,证明了这些拓扑关系具有完备性。实践表明,利用完备拓扑关系,不仅可以保证推导分析算法的正确性,也能极大简化复杂线对象与体对象间拓扑关系的分析。 相似文献
11.
Hilderick A. van der Meiden Author Vitae Willem F. Bronsvoort Author Vitae 《Computer aided design》2007,39(8):652-662
Parametric and feature-based CAD models can be considered to represent families of similar objects. In current modelling systems, however, the semantics of such families are unclear and ambiguous.We present the Declarative Family of Objects Model (DFOM), which enables us to adequately specify and maintain family semantics. In this model, not only geometry, but also topology is specified declaratively, by means of constraints. A family of objects is modelled by a DFOM with multiple realizations. A member of the family is modelled by adding constraints, e.g. to set dimension variables, until a single realization remains. The declarative approach guarantees that the realization of a family member is also a realization of the family.The realization of a family member is found by solving first the geometric constraints, and then the topological constraints. From the geometric solution, a cellular model is constructed. Topological constraints indirectly specify which combinations of cellular model entities are allowed in the realization. The system of topological constraints is mapped to a Boolean constraint satisfaction problem. The realization is found by solving this problem using a SAT solver. 相似文献
12.
Following the continuous increase in computational power of consumer hardware, interactive virtual environments have been recently enriched with more and more complex deformable objects. However, many physics engines are still very limited in the way they handle interacting rigid and deformable objects. This paper proposes a constraint‐based approach to real‐time simulation of coupled rigid and deformable objects capable of providing two‐way interactions. Similar techniques have seen widespread usage for either rigid or deformable objects, but not for the simultaneous simulation of both. By extending such approaches, we show not only how interaction is possible but also how it can be performed at real‐time rates. We address contact response and also show how to implement typical constraints to enforce limitations in the degrees of freedom and to enhance the dynamical properties of deformable objects. The method is easily integrated into existing physics engines that use similar constraint solvers and is independent on the kind of deformable object paradigm chosen. The provided simulation results show that the method is fast and effective in handling contacts between rigid and deformable objects and in simulating friction and other kinds of constraints. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
13.
The presentation of multimedia data is not only characterized by precise temporal constraints; also spatial constraints must be taken into account. An important requirement in multimedia systems is thus the integrated modeling of spatio-temporal constraints. Moreover, it is important to devise methods for checking the consistency of the specified constraints. In this paper, we first propose a spatio-temporal object graph (STOG) model that provides an integrated and graphical representation of spatio-temporal constraints. Second, we investigate consistency conditions between spatial and temporal constraints expressed in the STOG model. Then, we present a prototype system implementing the proposed model. 相似文献
14.
采用约束关系依赖图(CRDG)表达耦合约束之间的依赖关系,从而建立数值与符号耦合约束模型.提出耦合约束的求解算法:对CRDG进行最小独立子图分解,对存在耦合约束的子图用"孪生变量法"进行一阶解耦,对没有耦合约束的子图用传统方法进行独立求解,求解之后再对孪生变量进行等效性验算.该耦合约束模型及其求解算法拓展了传统约束理论,实现了教学求解和推理求解有机地结合. 相似文献
15.
Improvements in computer-aided design (CAD) tools can significantly increase designer productivity, since the ability to explore a variety of possible designs quickly and effectively is essential for a designer. Using an optimization tool, systematic exploration of design spaces can be achieved readily. The general goal of the work presented here is to aid design by combining the strengths of optimization techniques with those of CAD systems. The specific objective of this paper is to introduce goal directed geometry (GDG) as a computational framework for parametric design, aiding the formulation of engineering problems with geometric considerations and their solution with a multi-objective optimization package. Using GDG, What if questions can be posed and answered in a systematic fashion. Specific issues to be addressed include the development of a general parametric design problem formulation, development of static and dynamic geometric non-interference constraints for use in this formulation, and investigation of the efficacy of the adaptive linear programming (ALP) multiobjective optimization algorithm in solving such problems. Two examples are presented, one each to illustrate the use of the static and dynamic non-interference constraints. Results demonstrate that the GDG formulation can be applied readily to a wide variety of parametric design problems. Additionally, the ALP algorithm successfully navigates around geometric constraints, although care must be taken when linearizing highly non-linear design spaces. 相似文献
16.
Laying out objects with geometric and physical constraints 总被引:1,自引:0,他引:1
Modeling scenes involves two tasks:object modeling andobject layout. This paper focuses on object layout and proposes a constraint-based approach which yields a powerful object layout environment. The approach uses collision detection and physical simulation to ensure geometric and physical consistency of the resulting scenes, such as no interpenetration, and physical stability of the objects. A prototype system is developed, providing six basic operations; PUT, PUSH/PULL, TURN/TILT, PICK-UP, TRANSLATE, and ROTATE. The system: ensures geometric and physical consistency; provides easy-to-use operations analogous to object placement in real life; allows twodimensional control easily specified by mouse. Interactive speed is achieved on graphics workstations by using rasterized collision detection and simple quasi-static motion simulation. The system is interfaced to modeling/rendering/animation systems, and realizes an integrated environment for object modeling, object layout, rendering, and animation. We describe several scenes that have been modeled using the system and argue that these experiments confirm that the scene modeling task is greatly simplified by our constraint-based approach. 相似文献
17.
Approximate analysis of binary topological relations between geographic regions with indeterminate boundaries 总被引:9,自引:0,他引:9
F. Benjamin Zhan 《Soft Computing - A Fusion of Foundations, Methodologies and Applications》1998,2(2):28-34
The development of formal models of spatial relations is a topic of great importance in spatial reasoning, geographic information
systems (GIS) and computer vision, and has gained much attention from researchers across these research areas during the past
two decades. In recent years significant achievements have been made on the development of models of spatial relations between
spatial objects with precisely defined boundaries. However, these models cannot be directly applied to spatial objects with
indeterminate boundaries which are found in many applications in geographic analysis and image understanding. This article
develops a method for approximately analyzing binary topological relations between geographic regions with indeterminate boundaries
based upon previous work on topological spatial relations and fuzzy sets. In addition, examples are given to demonstrate the
method and related concepts. It is shown that the eight binary topological relations between regions in a two-dimensional
space can be easily determined by the method. 相似文献
18.
Qualitative relations between moving objects in a network changing its topological relations 总被引:1,自引:0,他引:1
Matthias Delafontaine Nico Van de Weghe Philippe De Maeyer 《Information Sciences》2008,178(8):1997-2006
The Qualitative Trajectory Calculus on Networks (QTCN) defines qualitative relations between two continuously moving point objects (MPOs) moving along a network. As prevailing in other research, this network is presumed static in QTCN. Actually, in many cases, networks are dynamic entities. For example in a road network, the opening of a bridge can temporarily close the connection between two junctions; traffic jams and traffic lights increase the time needed to travel from A to B. Therefore, it is interesting to examine what happens with qualitative relations between two continuously moving point objects if there are changes in the network. In this paper, we introduce QTCDN′, being the Qualitative Trajectory Calculus on Changing Networks able to handle topological network changes. Potential applications of the calculus in transportation are highlighted, clearly illustrating the usefulness of the calculus. 相似文献
19.
具备偏序关系的实时调度要求调度算法产生的执行序列既要满足任务的实时约束,又要满足任务间执行的偏序约束。基于并行拓扑排序,提出一种新的在线调度算法,该算法通过同时考察任务间执行的串行性和并行性来进行优先级设置,能够处理释放时间任意的任务集。给出该算法的原理和设计,并通过示例分析和比较对算法进行验证。 相似文献
20.
Kemal Egemen Ozden Kurt Cornelis Luc Van Eycken Luc Van Gool 《Computer Vision and Image Understanding》2004,96(3):453
The 3D reconstruction of scenes containing independently moving objects from uncalibrated monocular sequences still poses serious challenges. Even if the background and the moving objects are rigid, each reconstruction is only known up to a certain scale, which results in a one-parameter family of possible, relative trajectories per moving object with respect to the background. In order to determine a realistic solution from this family of possible trajectories, this paper proposes to exploit the increased linear coupling between camera and object translations that tends to appear at false scales. An independence criterion is formulated in the sense of true object and camera motions being minimally correlated. The increased coupling at false scales can also lead to the destruction of special properties such as planarity, periodicity, etc. of the true object motion. This provides us with a second, ‘non-accidentalness’ criterion for the selection of the correct motion among the one-parameter family. 相似文献