Polygon-based hidden surface elimination algorithms: serial and parallel

Chapter 1 introduces the need for rapid solutions of hidden surface elimination (HSE) problems in the interactive display of objects and scenes, as used in many application areas such as flight and driving simulators and CAD systems. It reviews the existing approaches to high-performance computer graphics and to parallel computing. It then introduces the central tenet of this thesis: that general purpose parallel computers may be usefully applied to the solution of HSE problems. Finally it introduces a set of metrics for describing sets of scene data, and applies them to the test scenes used in this thesis. Chapter 2 describes variants of several common image space hidden surface elimination algorithms, which solve the HSE problem for scenes described as collections of polygons. Implementations of these HSE algorithms on a traditional, serial, single microprocessor computer are introduced and theoretical estimates of their performance are derived. The algorithms are compared under identical conditions for various sets of test data. The results of this comparison are then placed in context with existing historical results. Chapter 3 examines the application of MIMD style parallelism to accelerate the solution of HSE problems. MIMD parallel implementations of the previously considered HSE algorithms are introduced. Their behaviour under various system configurations and for various data sets is investigated and compared with theoretical estimates. The theoretical estimates are found to match closely the experimental findings. Chapter 4 summarises the conclusions of this thesis, finding that HSE algorithms can be implemented to use an MIMD parallel computer effectively, and that of the HSE algorithms examined the z-buffer algorithm generally proves to be a good compromise solution

Object based manipulation with 3D scenes in mobile environment

The increasing power and display resolution of mobile devices allow the user nowadays to work with 3D information in mobile environment. The use of this new technology brings some new problems that need an urgent solution. One of them has its roots in the fact that common users are not trained to work in 3D graphical environment in general. The main obstacle for a common user is the fact that 3D environment offers too much freedom for object manipulation in comparison with situation in 2D environment. There are various solutions to this problem but usually they do not handle efficiently the problem of navigation in 3D environment in context of handling appropriate information density on a small screen on a mobile device. Our approach is based on transformation of a 3D scene in 2D representation in order to decrease freedom of movement during navigation in the scene. The navigation (and other types of interaction) is performed in 2D environment - the information acquired during interaction is transformed back into 3D form (into 3D object space). In such a way the user can manipulate with single objects in various modes (e.g. the user can change focus on various objects what might e.g. result in their temporary elimination from the scene). The work in 2D in mobile environment requires some special features that are not considered in standard environment. Especially critical is zooming. Zooming in raster form could change the picture on a small screen into completely unusable representation (pixels will be transformed in tiles that will be difficult to perceive). Solution to this (and to other related problems) is the use of SVG format to handle 2D scene representation. The main advantage of SVG is that it is object oriented and supports zooming, interaction with objects, scene annotation and manipulations with objects. The process of scene transformation and manipulation with objects is distributed between the server and mobile device. The transformation is performed on the server side. The resulting 2D representation of the scene is sent to mobile device where the visualization is performed. The user can interact with the picture on the mobile device with interaction techniques available on mobile devices. As the SVG is XML based format, the Cascading Style Sheets can be used to style all graphical elements. Therefore each object can be visualized in different mode (solid, transparent, semitransparent). These modes could be changed interactively. This feature (interactive change of modes) substitute in certain sense some functions available for avatars during their walkthroughs when performed in standard 3D environment (e.g. "having look behind corner" etc.). The user interaction in 2D environment is rather limited in comparison with standard 3D interaction but it is less demanding for the user. On the other hand it brings better picture quality due to SVG features applied e.g. during the process of zooming

Cybervandalism or Digital Act of War? America\u27s Muddled Approach to Cyber Incidents Will Not Deter More Crises

If experts say a malicious [cyber] code \u27 has similar effects to a physical bomb, \u27 and that code actually causes a stunning breach of global internet stability, is it really accurate to call that event merely an instance of a cyber attack ? Moreover, can you really expect to deter state and non-state actors from employing such code and similarly hostile cyber methodologies if all they think that they are risking is being labeled as a cyber-vandal subject only to law enforcement measures? Or might they act differently if it were made clear to them that such activity is considered an armed attack \u27 against the United States and that they are in jeopardy of being on the receiving end of a forceful, law-of-war response by the most powerful military on the planet? Of course, if something really is just vandalism, the law enforcement paradigm, with its very limited response options, would suffice. But when malevolent cyber activity endangers the reliability of the internet in a world heavily dependent on a secure cyberspace, it is not merely vandalism. Rather, it is a national and international security threat that ought to be characterized and treated as such. Unfortunately, the United States\u27 current approach is too inscrutable and even contradictory to send an effective deterrence message to potential cyber actors. This needs to change

Building geometric models with hand-drawn sketches

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1998.Includes bibliographical references (p. 49-51).Architects work on drawings and models, not buildings. Today, in many architectural practices, drawings and models are produced in digital format using Computer-aided Design (CAD) tools. Unquestionably, digital media have changed the way in which many architects perform their day to day activities. But these changes have been limited to the more prosaic aspects of practice. To be sure, CAD systems have made the daily operations of many design offices more efficient; nevertheless, they have been of little use - and indeed are often a hindrance - in situations where the task at hand is more conjectural and speculative in nature, as it is during the early stages of a project. Well-intentioned efforts to insinuate CAD into these aspects of practice have only served to reveal the incongruities between the demands of designer and the configuration of the available tools. One of the chief attributes of design practice is that it is action performed at a distance through the agency of representations. This fundamental trait implies that we have to understand how computers help architects describe buildings if we are to understand how they might help architects design buildings. As obvious as this claim might seem, CAD programs can be almost universally characterized by a tacit denigration of visual representation. In this thesis, I examine properties of design drawings that make them useful to architects. I go on to describe a computer program that I have written that allows a designer to build geometric models using freehand sketches. This program illustrates that it is possible to design a software tool in a way that profits from, rather than negates, the power of visual representations.by Ewan E. Branda.M.S

Analyzing Accidents in Civil Construction for Safety Work at Height

In civil construction any and all services must be performed objectively and safely, especially the services at the height of the painter, where the employee is more exposed to the risk of falls and impacts of the user\u27s own objects on lower limbs. Both the employee and the employer are responsible for everything that happens at the construction site, the employer providing safety devices and plans to minimize the rich of accidents while performing the services and the employee must obey any and all safety orders and plans aimed at not only your physical integrity but that of your colleagues doing services around you. Therefore this work will address the NR-6 regulations dealing with single use equipment, NR-18 which work conditions and environment in the construction industry and NR-35 work at height, which regulate service at height with the main focus

Kindergarten Social and Emotional Learning Development

Social and Emotional Learning Skills for students who attend Community Partnership for Youth after-school program