Collision Detection for Deformable Objects

Interactive environments for dynamically deforming objects play an important role in surgery simulation and entertainment technology. These environments require fast deformable models and very efficient collision handling techniques. While collision detection for rigid bodies is well investigated, collision detection for deformable objects introduces additional challenging problems. This paper focuses on these aspects and summarizes recent research in the area of deformable collision detection. Various approaches based on bounding volume hierarchies, distance fields and spatial partitioning are discussed. In addition, image‐space techniques and stochastic methods are considered. Applications in cloth modeling and surgical simulation are presented.     

Surface modeling with ternary interpolating subdivision

In this paper, a new interpolatory subdivision scheme, called ternary interpolating subdivision, for quadrilateral meshes with arbitrary topology is presented. It can be used to deal with not only extraordinary faces but also extraordinary vertices in polyhedral meshes of arbitrary topologies. It is shown that the ternary interpolating subdivision can generate a C¹-continuous interpolatory surface. Some applications with open boundaries and curves to be interpolated are also discussed.     

基于单片机的进给驱动系统的设计

介绍了一种采用步进电机作为驱动元件的进给驱动装置。通过ATMEL89C52单片机对步进电机进行细分控制,给出了硬件、软件设计框图和一个典型的细分驱动应用电路。该电路已成功用于某步进电机伺服系统中。     

基于脉宽调制步进电机细分控制的拖动研究

目的　研究提高验光仪测量精度的理论方法 .方法　采用脉宽调制步进电机细分控制技术 .结果设计了一套电路和软件算法系统 ,能使测量精度提高 .结论　该方法简单可行 ,成本低 ,可靠性高 ,同时也降低了机械结构设计的技术难度     

Taxonomy of interpolation constraints on recursive subdivision surfaces

Published online: 14 May 2002     

Smooth multiple B-spline surface fitting with Catmull%ndash;Clark subdivision surfaces for extraordinary corner patches

This paper presents an algorithm for simultaneously fitting smoothly connected multiple surfaces from unorganized measured data. A hybrid mathematical model of B-spline surfaces and Catmull–Clark subdivision surfaces is introduced to represent objects with general quadrilateral topology. The interconnected multiple surfaces are G ² continuous across all surface boundaries except at a finite number of extraordinary corner points where G ¹ continuity is obtained. The algorithm is purely a linear least-squares fitting procedure without any constraint for maintaining the required geometric continuity. In case of general uniform knots for all surfaces, the final fitted multiple surfaces can also be exported as a set of Catmull–Clark subdivision surfaces with global C ² continuity and local C ¹ continuity at extraordinary corner points. Published online: 14 May 2002 Correspondence to: W. Ma     

Occlusion Culling Algorithms: A Comprehensive Survey

In this paper, occlusion culling techniques that appeared in the last decade are reviewed. Occlusion culling techniques are responsible for reducing the polygons rendered by the graphics hardware with the target of achieving real-time rendering. The various techniques are discussed in detail and a synopsis table with their main characteristics is given.     

A fast algorithm for an envelope construction of a huge set of topologically consistent polygons

This paper describes an efficient algorithm for the determination of an envelope of a set of polygons. The polygons have to be aligned along their borders – the case which, for example, appears in geographic information systems. The edges, which belong to two neighbouring polygons, are called twin edges, and are eliminated first. To accelerate the geometric search, a two-level uniform plane subdivision structure is proposed. The remaining non-twin edges belong to the envelope, and they have to be joined to form the simple polygons at the end. For this task, a new algorithm has been developed. At the end, spatial relationships between resulting polygons are established. The whole algorithm for envelope determination works in expected time O(n log n) using O(n) memory space, where n is the total number of edges belonging to the input polygons. In the last part of the paper, practical results using data from a geographical database are considered.     

An Event-Based Approach to Spatio-Temporal Data Modeling in Land Subdivision Systems

The spatio-temporal database for a collaborative decision making system supporting land subdivision is event-driven. Both various states of spatial objects and the events causing the objects change need to be recorded and manipulated in the database. To achieve this, the authors analyzed the characteristics of events in land subdivision process and studied how events affect the states of spatial objects. An event-based approach was proposed to develop the spatio-temporal data model for the GIS-based computer-supported collaborative work (CSCW) land subdivision system. A formal specification of event and its operators was introduced for describing the execution of events and their sequence. The spatio-overlap and time-meet constraints between parent-child parcels are proposed to represent the linkage between different states of land parcels. With this approach, events and the causal relations between events and states can be recorded and managed in the spatio-temporal database in a land subdivision system. In addition, a new way for simulating system work-flow is also suggested.     

Polygon visibility ordering via Voronoi diagrams

Visibility determination is one of the oldest problems in computer graphics. The visibility, in terms of back-to-front polygon visibility ordering, is determined by updating a priority list as the viewpoint moves. A new list-priority algorithm, utilizing a property of Voronoi diagrams, is proposed in this paper. The operation is in two phases. First, in a pre-processing phase the scene is divided into Voronoi cells. A sub-list associated with each cell contains references to those polygons that intersect with it. The polygons are assigned a fixed set of view-independent priority orders within the cluster. Last, an interactive phase sorts the clusters according to the depth value of each Voronoi site. The most time-consuming work is performed during the pre-processing phase that only has to be executed once for the scene. Since all the polygons in a cell are pre-computed to obtain the fixed priority order within the cluster, a relatively simple task is left in the interactive phase, which is only to sort the clusters repeatedly when the viewpoint is changed. This method contains performance benefits that make it better shaped than previous BSP based methods.