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.     

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.     

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。     

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.     

GosiP: A GKS3D Shell for PHIGS

Gosip is an implementation of a GKS-3D level 2c interface to PHIGS. It allows GKS applications to run on PHIGS platforms, offering performance and portability across a wide range of high-performance 3D workstations. Compatibility of the standards is reviewed. A selection of design solutions is given for the problems of error processing, non-retained primitives and attribute management. The concepts of Workstation Display Session and atmbute state are introduced. Some comments are made on implementation dependencies, performance and portability.     

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⁺. .     

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.     

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.     

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.     

Factoring a Homogeneous Transformation for a more Efficient Graphics Pipeline

We identify an intermediate coordinate system situated between world coordinates and display coordinates, which exhibits unique features for lighting calculations and for clipping in homogeneous coordinates. Our key contribution is an algorithm for extracting such a coordinate system from a homogeneous viewing transformation that relates WC to DC. The algorithm is based on factoring the transformation into a product of a Euclidean factor and a sparse (computationally cheap) but non-Euclidean factor.
A particularly strong application of the proposed technique is the graphical processing of curved surface primitives, such as what is needed in the PHIGS PLUS viewing pipeline. Furthermore, in PHIGS PLUS the graphical data is retained by the graphics system, therefore, it is possible to perform the factoring of the viewing transformation at creation time, and to take advantage of this factored form at traversal time.     

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.     

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.     

Some Remarks on the Modelling Gip Problem

The modelling clip as proposed for example in PHIGS is mathematically analyzed and a method to perform it is proposed. The method has the particular edvantage of avoiding all possible singularities appearing in the course of a projective transformation. Additionally, further optimizations in the implementation of the whole output pipeline are proposed.     

Top Draw: A Structure Network Visualiser for PHIGS

The Programmer's Hierarchical Interactive Graphics System (PHIGS) is an International Standard for computer graphics. PHIGS provides a flexible mechanism for creating hierarchical models from collections of directed acyclic graphs known as 'structure networks'. In practice, the combination of powerful data structuring facilities and the ability to dynamically edit structure networks can lead to a potential complexity which makes models difficult to manage and maintain reliably.
This paper presents TopDraw , a portable programming tool for visualising PHIGS structure networks, by automatically documenting their topology using diagrams. Drawing tidy representations of graphs algorithmically is a difficult problem, and most existing systems are large, complex and speciallsed The alternative approach taken in TopDraw is to use a fast, straightforward algorithm supplemented when necessary by an interactive 'tidief. A novel feature of TopDraw is that the diagrams it produces are themselves PHIGS structures, which the application may edit and manipdate as required. TopDraw is a component of the PHIGS Toolkit , an emerging set of portable integrated tools for PHIGS environments.     

Modelling Clip: Some More Results

The modedling clip of the PHIGS ISO Standard is mathematically analysed. The most important result of this analysis is the fact that the projective image of a modding clip body (that is a not necessarily bounded convex body in space) is simply the union of two convex bodies. Furthermore, it will also be proved that in some cases one of these two bodies is empty. This fact makes the implementation of the modelling clip fairly straightforward and makes it also possible to use all already existing results on clipping against general convex bodies without change.     

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.     

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.     

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.