An Implementer's View of PHIGS

The Programmer's Hierarchical Interactive Graphics System (PHIGS) specifies an interface for programming device-independent computer graphics applications. After a brief review of PHIGS concepts, an experimental environment used to study and evaluate the proposed standard is presented. The basic structure and distribution of function in this PHIGS implementation is discussed. We describe the architecture of a device-independent environment designed to realize the performance essential to the adequate functioning of a PHIGS implementation. The results presented emphasize the PHIGS output model. Full utilization of workstation processing capabilities, minimization of host/workstation interaction and efficient data management are key to our implementation.     

Ray Tracing and Graphics Standards

Existing standards for three-dimensional graphic representations are unable to produce any realistically shaded images (except PHIGS PLUS, which provides discrete shading only). Ray Tracing or Radiosity are not taken into account up to this time. This article is intended to show one way to integrate the Ray Tracing technique into the pipeline of the graphics standards GKS-3D and PHIGS. No modifications of the viewing concepts are required by our implementation.     

Integrating PHIGS and User Interface Systems

The past five years has seen an explosion of rich and effective user interface management systems and toolkits and an increase in the expectations regarding application portability. Nearly a decade old, the PHIGS input model is inadequate in the face of this variety. "Fixing PHIGS" input would be a long and arduous task. Instead, PHIGS should be adapted to cooperate, not compete, with user interface systems. This can be done in two ways. An application can use both PHIGS input and input from a user interface system to accomplish its goals. Alternatively, an application can use input only from a user interface system, but in this case it needs utilities in PHIGS to gain access to information only PHIGS can supply. Specifically the utilities are needed for application-initiated picking and for coordinate mapping.     

PHIGS: A Standard, Dynamic, Interactive Graphics Interface

The Programmer's Hierarchical Interactive Graphics System (PHIGS) is a draft standard for computer graphics programming. PHIGS is useful for applications that manipulate complex displays of 2D or 3D data in a highly interactive environment. This is done through the hierarchical data organization and flexible editing capabilities provided in PHIGS. This article describes the goals and underlying model of PHIGS, reviews its capabilities, and provides some brief application examples. The similarities and differences of PHIGS and GKS are discussed.     

New Methods for Improving the GKS Fill Area Output Primitive

The fill area primitive is one of the most powerful primitives of GKS and its derivatives (GKS-3D, PHIGS etc.). Since its specrfication is extremely general, it is important to explore new approaches to achieve higher performance in its implementation. In this paper fast algorithms are presented for special situations, which can be included, together with appropriate tests, into a complete GKS output pipeline. As a result, a speed improvement With a factor of two may be achieved in important practical cases.     

The Priority Tree, a HL/HSR Approach for PHIGS

The Programmer's Hierarchical Interactive Grahics System (PHIGS) specifies an interface for programming device-independent computer graphics applications. PHIGS provides a powerful data grouping mechanism, called the PHIGS structure, that may be used to model the geometry of 3D objects. Hidden Line/Hidden Surface Removal (HL/HSR) is a required process to produce realistic solid views of the modeled objects. Modeling clip is an essential process for viewing a clipped portion of the modeled objects. A technique is presented that provides HL/HSR and modeling clip as added utilities to PHIGS. The technique is based on the Binary Space Partitioning (BSP) tree (sometimes called priority tree), and involves a back to front sorting of the primitives of a PHIGS structure network to another PHIGS structure. Modeling clip is achieved by limiting the sorting to those primitives in a specified clip ping region of the object space. The resulting structure when displayed on a raster device produces a realistic view of the possibly clipped object that was originally modeled by the PHIGS structure network.     

GKS Programming in a PHIGS Environment

GKS is an international standard for the functional interface to 2D graphics, whilst PHIGS is currently an ISO work item for 2D and 3D graphics. In addition, PHIGS allows improved control over structuring graphics data in the system. With a new work item, the upwards compatability from GKS to PHIGS is being called into question. This paper is an attempt to give direction to these discussions by listing the implications of introducing a software layer between a GKS application program and a PHIGS environment on which this application is to be run. It is intended to highlight differences between the systems and to answer questions such as, “How compatible?”, “Is it possible?”, “How much does the software layer have to do?”, etc.     

A critical evaluation of PEX

PEX, the PHIGS extension to the X Window System, is evaluated in the context of assumptions inherent in the PHIGS output, modeling, input, user interface, and system environment models. Problems not previously discussed arise when examining PEX this way. The problems not only pertain to the implementation of PEX, but also to implementing a 3-D library in a distributed windowing system in general. The University of Illinois PEX implementation serves as a reference to discuss the solutions proposed     

Parametric Surfaces in PHIGS PLUS: a New Chance for Patterning and Hatching?

The Polygon Fill style PATTERN and HATCH, which are quite successful in 2D graphics standards as GKS¹ and CGI² have proved to be less suitable for 3D graphics standards as GKS-3D³ and PHIGS⁴. However, the emerging standard PHIGS PLUS⁵ offers a unique chance to successfully employ these Interior Styles (under another name and in a slightly different form), because PHIGS PLUS supports a.o. topologically rectangular parametric surfaces In this article it is shown how these Interior Styles could be efficiently applied to curved surfaces in PHIGS PLUS. In addition, the possible interaction between the tessellation method and the patterning is shown.     

Guidelines for Determining When to Use GKS and When to Use PHIGS

GKS, GKS-3D, and PHIGS are all approved ISO standards for the application programmer interface. How does a system analyst or programmer decide which standard to use for his application? This paper discusses the range of application requirements likely to be encountered, explores the suitability of GKS and PHIGS for satisfying these requirements, and offers guidelines to aid in the decision process.     

A Method for the Representation, Evaluation and Display of CSG Models in PHIGS and PHIGS+

The Programmer's Hierarchical Interactive Graphics System (PHIGS) is about to become a standard graphics system ^† which caters for the definition, display and modification of two and three-dimensional graphical data.
PHIGS , however, is mainly a wireframe system, and the PHIGS⁺ , extensions to it have been put forward to allow the incorporation of shaded 3D graphics into PHIGS. ,
One area that is important to a large constituency and which has so far not been considered in PHIGS , and PHIGS⁺ , is that of solid modelling. This paper addresses one aspect of solid modelling by describing a simple method for the representation, evaluation and display of Constructive Solid Geometry (CSG) models in PHIGS , and PHIGS⁺. .     

基于PHIGS的层次图形数据库系统

程序员级的交互式层次图形系统支持动态的交互和层次结构的组织。实现图形系统的一个重要方面是图形模型的数据结构。本文论述了一个集中式图形数据库的设计与实现，该系统是一个实验性的基于ＰＨＩＧＳ的层次数据库系统。其设计的特点是此数据库可以被若干个应用程序共享。     

A Library for Developing PHIGS Programming Tools in a PEX Environment

The merger of three-dimensional graphics with the X Window System has recently been standardized by adapting PHIGS, the Programmer's Hierarchical Interactive Graphics System, to the X Window System with PEX, the PHIGS Extension to X. The standard programming library for PEX has been defined to be identical to PHIGS PLUS allowing PHIGS programs to port directly to the X environment. X uses a client server model to run applications as client processes which communicate with a server to perform graphical display and input. For improved performance, the PEX extension defines new server resources to reduce network traffic and to take advantage of graphics hardware existing on high-end servers. A side effect of this distributed model of computation is a distribution of PHIGS structures leading to a relaxation of the exclusive access which a PHIGS application usually maintains over its Central Structure Store. We exploit the distributed nature of a PEX/PHIGS client's Central Structure Store to provide access to it for other applications besides the originating PEX/PHIGS client. We refer to these other applications as tools since one of our primary goals is to create development tools for PHIGS programmers. Rather than concentrate on particular debugging tools, we focus upon easing the process of actually developing tools. Our goal is to supply a collection of routines which can be used by PHIGS programmers to create custom tools or other programs which require access to the graphics data of remote PHIGS processes. Our Tool Development Library provides the PHIGS programmer a small number of management routines which orchestrate the connection and mapping to the data of one or more remote PHIGS applications. Manipulation of remote PHIGS structures is accomplished just as easily as local operations and is performed using standard PHIGS calls. The remote application being accessed requires no changes to its source code. Obvious uses for the Tool Development Library are in the construction of PHIGS tools such as structure browsers, editors and debugging aids. Less obvious is the potential for developing collections of cooperating graphics applications which share graphics data.     

BD-GKS3D图形软件的设计与实现

BD-GKS3D是按图形国际标准GKS-3D(ISO 8805)开发的三维图形支持软件。本文讨论了该软件的设计原则:符合国际标准及尽可能高效率。还讨论了实现的策略,包括二维GKS与三维兼容问题,裁剪与变换,实现环境,图段的数据结构及三维输入等内容。最后对开发BD-GKS3D的工作量、与PHIGS,CGI的关系等作了说明。     

The Computer Graphics Virtual Device Interface

Decisions about which functions to include in systems like PHIGS and GKS-3D are based primarily on the tasks users want performed, such as direct support for 3D operations. The design criteria for device interface systems like the Computer Graphics Virtual Device Interface, however, must be based on what is feasible to do in a device, while still considering how to decompose tasks into hardware-realizable functions. Complicating these design decisions is the wide range of existing device technology and the breadth of usage models imposed by different task-oriented software.     

三维图形API的分析与比较

本文在层次结构,代码可移植性,数据可移植性,性能,功能及易用性等方面对目前主流的三种三维图形应用编程接口进行了分析与简单的比较。     

Are PHIGS and GKS Necessainly Incompatible?

The compatiblility issues that are of concern through the graphics industry are particularly serious in the relationship of GKS, GKS-3D, and nowcomer PHICS. The point made in this article is that PHIGS can be brought more into line with the GKS standards, offering a broader range of applications to both sets of users.     

A Note on 3D-Clip Optimisation

In order to optimize the transformation-clipping-pipeline of PHIGS or GKS-3D it is sometimes necessary to determine whether a plane intersects a perpendicular volume or not. The solution to this problem is not very complicated. This paper offers a more effective procedure that handles this task.