CAD Data Transfer for Solid Models

This is one out of a series of books which present the result of ESPRIT project 322 "CAD Interfaces (CAD*I)". This volume concentrates on the work done on the transfer of CAD models, especially so-called solid models. The book gives an introduction to the state of the art prior to the CAD*I project, describes the approach taken by the project, and presents the results obtained. Information is also given on the interrelationship with the international standardization activities in this field. The book is primarily intended for readers who are interested in - the problems encountered in the transfer of solid models, - the various techniques for implementing processors for this purpose, - the specific implementations of interface processors for several CAD systems, - the state of the art reached after completion of the project, and - the relationship between the CAD*I project and the development of the international standard for external representation of product definition data STEP.

Project Overview.- The Transfer of Solid Models.- 1. Introduction.- 1.1 The evolution of concepts and specifications for CAD data exchange.- 1.1.1 IGES.- 1.1.2 Other standards: VDAFS and SET.- 1.1.3 The need for a new standard.- 1.2 Solid modelling techniques.- 2. The CAD*I approach to solid model transfer.- 2.1 General principles.- 2.2 The specification tools.- 2.2.1 Features of the CAD*I specification language HDSL.- 2.2.2 The specification language for the physical file format.- 2.3 Specification of the CAD*I reference model.- 2.3.1 Content.- 2.3.1.1 Attribute types for general use.- 2.3.1.2 General data base structure.- 2.3.1.3 Referencing mechanisms.- 2.3.1.4 Geometric model entities.- 2.3.1.5 Solid models.- 2.3.1.6 General grouping mechanism.- 2.3.1.7 Test data elements.- 2.3.1.8 Miscellaneous.- 2.3.1.9 Parametric modelling.- 2.3.2 Static models and parametric models.- 2.4 Implementation levels.- 2.4.1 The geometric modelling levels.- 2.4.2 The assembly structure.- 2.4.3 Parametric models and macros.- 2.4.4 References.- 2.5 The specification of semantic meaning.- 2.5.1 Generic semantics of the CAD.’ data structures.- 2.5.1.1 Creation of data structure elements.- 2.5.1.2 Deletion of data structure elements.- 2.5.1.3 Modification of attributes.- 2.5.1.4 Navigation in the data structure.- 2.5.2 The semantics of post-processors.- 2.5.3 The static semantics of geometric entities.- 2.5.3.1 Curves and surfaces.- 2.5.3.2 Solids.- 2.5.4 Linear transformation of geometric models.- 2.6 Aspects of the physical file format.- 2.6.1 The transport aspect.- 2.6.2 The presentation aspect.- 2.7 Processor implementation.- 2.8 Access to CAD system data bases.- 3. General implementation problems.- 3.1 Access to the CAD system data base.- 3.1.1 Programming interface.- 3.1.2 Access via files.- 3.2 Mapping problems.- 3.3 Inference of the original meaning: Euclid primitives.- 3.4 Missing CAD*I entity example: Pyramid in Bravo3.- 3.5 Implicit model conversion example: CSG input to a B-rep system.- 3.6 Deviations from the reference model: The Bravo3 one-sided Boolean tree.- 3.7 The overlap problem in CSG modelling: a Bravo3 example.- 3.8 Problems related to Boolean operations in Proren2 and Technovision.- 3.9 The effect of truncation errors: receiving boxes in Bravo3.- Specific Implementations.- 4. The CAD*I processors for Schlumberger’s Bravo3.- 4.1 System description.- 4.2 Internal representation of CAD models.- 4.3 Existing interfaces.- 4.4 Embedding the processors into the Bravo3 environment.- 4.5 The pre-processor.- 4.5.1 Instances.- 4.5.2 Names.- 4.5.3 Features.- 4.5.4 The mapping from Bravo design input to CAD*I format.- 4.6 Examples of pre-processor conversions.- 4.6.1 Parallelepiped.- 4.6.2 Polyhedron.- 4.6.3 Right Angle Wedge.- 4.6.4 Sphere.- 4.6.5 Right Circular Cylinder.- 4.6.6 Truncated Right Cone.- 4.6.7 Solid Torus.- 4.6.8 Arbitrary Slab.- 4.6.9 Surface of revolution.- 4.7 The post-processor.- 4.8 Examples of post-processor conversions and approximations.- 4.8.1 Examples of the command input file.- 4.8.2 Some details to post-processor transactions.- 4.8.3 Special features.- 4.9 The formal Bravo3 solid model transfer schema.- 4.9.1 Pre-processor schema.- 4.9.1.1 General data base structure.- 4.9.1.2 Points and curves.- 4.9.1.3 Constructive solid geometry.- 4.9.1.4 General grouping mechanism.- 4.9.1.5 Placement and instancing.- 4.9.1.6 Miscellaneous.- 4.9.2 Post-processor.- 4.9.2.1 General data base structure.- 4.9.2.2 Points and curves.- 4.9.2.3 Constructive solid geometry.- 4.9.2.4 General grouping mechanism.- 4.9.2.5 Placement and instancing.- 4.10 Test results.- 5. The CAD*I processors for IBM’s Catia.- 5.1 System description.- 5.2 Existing interfaces.- 5.3 Internal representation of CAD models.- 5.4 Embedding the processors in the Catia environment.- 5.4.1 Hardware and operating system.- 5.4.2 Programming Language and Compiler.- 5.4.3 CATGEO routines to access the Catia database.- 5.4.4 Standardisation of routine names.- 5.4.5 Internal programme documentation.- 5.5 The pre-processor.- 5.5.1 Implementation levels.- 5.5.2 The formal Catia solid model transfer schema.- 5.5.3 Programme description.- 5.6 The post-processor.- 5.6.1 Implementation levels.- 5.6.2 The formal Catia solid model transfer schema.- 5.6.3 Programme description.- 5.7 Test results.- 6. The CAD*I processors for Matra Datavision’s Euclid.- 6.1 System description.- 6.2 Existing interfaces.- 6.3 Internal representation of CAD models.- 6.4 Embedding the processors into the Euclid environment.- 6.4.1 Pre-processor.- 6.4.2 Post-processor.- 6.5 The mapping from Euclid data structure to CAD*I data structure.- 6.5.1 Processing of Euclid solid primitives.- 6.5.1.1 Processing of the Euclid solid of revolution.- 6.5.1.2 Processing of special cases of Euclid polyhedron entities (BOX).- 6.5.1.3 Processing of general Euclid polyhedron entities.- 6.5.2 The processing of Euclid hybrid solids.- 6.5.3 The processing of the Euclid “figure” entities.- 6.6 The mapping from CAD*I data structure to Euclid data structure.- 6.6.1 Processing of information related to the neutral file.- 6.6.2 Processing of information related to the world.- 6.6.3 Processing of elementary geometric information.- 6.6.4 Processing of composite geometric information.- 6.6.4.1 Mapping of sweep entities to Euclid representations.- 6.6.4.2 Mapping of polyhedron entities to the Euclid polyhedron.- 6.6.5 Processing of structural information.- 6.7 Mapping problems in the pre-processor.- 6.7.1 Mapping problems with the Euclid primitives.- 6.7.2 Mapping problems with Boolean expressions in Euclid.- 6.7.3 Mapping problems with polyhedron entities in Euclid.- 6.8 Mapping problems in the post-processor.- 6.9 Possible enhancements of the processors.- 6.10 Test results.- 7. The CAD*I processors for DTH’s GDS.- 7.1 System description.- 7.2 User interaction and internal representation.- 7.3 Existing interfaces.- 7.4 The pre-processors.- 7.4.1 The data base traversal.- 7.4.2 Limitations.- 7.5 An example of pre-processor conversion.- 7.6 The post-processors.- 7.6.1 The data structure.- 7.7 An example of post-processor conversion.- 8. The CAD*I processors for SDRC’s Geomod.- 8.1 System description.- 8.2 Existing interfaces.- 8.2.1 IGES.- 8.2.2 Universal file.- 8.2.3 Programme files (log file).- 8.2.4 PEARL data base interface (PDI).- 8.2.5 Internal representation of CAD models.- 8.2.6 Object Representation.- 8.2.7 Polygonal model.- 8.2.8 Context-free geometry.- 8.2.9 Grouping data.- 8.3 The pre-processor.- 8.4 The post-processor.- 8.4.1 General concept.- 8.4.2 Generation of CSG Models.- 8.4.3 Generation of B-rep models.- 9. The CAD*I processors for Control Data’s Item.- 9.1 System description.- 9.2 Internal representation of CAD models.- 9.3 Existing interfaces.- 9.4 Embedding the processors into the Icem Modeller environment.- 9.5 The pre-processor.- 9.6 Examples of pre-processor conversions.- 9.6.1 Parallelepiped.- 9.6.2 Arbitrary polyhedron.- 9.6.3 Truncated right cone.- 9.6.4 Solid-cylinder.- 9.6.5 Sphere.- 9.6.6 Solid Torus.- 9.7 The post-processor.- 9.7.1 Examples of post-processor conversions and approximations.- 9.7.2 Special implementation features.- 9.8 Test results.- 10. The CAD*I processors for Isykon’s Proren2.- 10.1 System description.- 10.2 Existing interfaces.- 10.3 Internal representation of CAD models.- 10.3.1 The formal description of the internal model.- 10.3.2 The formal description of the CSG input language.- 10.3.2.1 The relation between CAD*I and Proren primitives.- 10.3.2.2 The operators.- 10.4 The B-rep pre-processor.- 10.4.1 Some problems in the pre-processor area.- 10.4.1.1 Pre-processor and geometrical problems.- 10.5 The post-processor for B-rep and polyhedron models.- 10.6 The post-processor for CSG models.- 10.7 Embedding the processors into the Proren2 environment.- 10.8 Test results.- 11. The CAD*I processors for Shape Data’s Romulus.- 11.1 System description.- 11.2 Existing interfaces.- 11.3 Mapping between CAD*I and Romulus.- 11.4 The processors.- 11.4.1 The pre-processor.- 11.4.2 The post-processor.- 11.4.3 Parsing the neutral file.- 11.4.4 Creating geometry.- 11.4.5 The temporary data structure.- 11.5 Concluding remarks.- 12. The CAD*I processors for Norsk Data’s Technovision.- 12.1 System description.- 12.2 User interaction and internal representation.- 12.3 Existing interfaces.- 12.4 The processors.- 12.4.1 Pre-processors.- 12.4.2 Post-processors.- 12.4.3 Implementation levels.- 12.5 Pre-processor architecture and implementation.- 12.6 Post-processor architecture and implementation.- 12.7 Program design and implementation strategies.- 12.8 Performance and other measurements on the CAD*I pre- and post-processors for Technovision.- 12.9 An example of a transfer test Technovision ? Proren ? Technovision.- 13. The CAD*I/STEP converters.- 13.1 CAD*I and STEP files for the CAD*I/STEP conversion test.- 14. Other implementations.- 14.1 Kismet.- 14.2 Bravo3 ROBOT.- 14.3 ROBCAD.- 14.4 Autocad.- 14.5 Oracle.- 14.6 GRASP.- 14.7 Weld Planning Module.- Software Development Tools and Test Parts.- 15. The CAD*I software tools.- 15.1 General architecture of pre- and post-processors.- 15.2 Common file access software for pre-processors.- 15.2.1 Files and common areas.- 15.2.2 Routine specification.- 15.3 The front-end of the CAD*I post-processors.- 15.3.1 Scanner.- 15.3.2 Parser.- 15.3.3 Type checking.- 15.4 Utility Software: The CADI metafile handler.- 16. The CAD*I test parts.- 16.1 Introduction.- 16.2 Classification of test parts.- International Standardisation.- 17. The interaction of CAD*I with ISO/TC184/SC4/WG1.- 17.1 Scope of the specification.- 17.2 Three-layer approach.- 17.3 Integration versus coexistence.- 17.4 The specification language.- 17.5 The neutral file format.- 17.6 CAD geometry and shape representation.- 17.6.1 Curves and surfaces.- 17.6.2 Solid models.- Transfer of CAD Files Via Computer Networks.- 18. Networks for communicating CAD information.- 18.1 Communication in general.- 18.2 Application of file transfer for CAD.- 18.2.1 Scope of feasibility study.- 19. Overview on available networks and protocols.- 19.1 Introduction.- 19.2 Networks.- 19.2.1 Public Data Networks.- 19.2.2 Local Area Networks.- 19.2.3 Academic and Research Networks.- 19.2.3.1 European Academic and Research Network (EARN).- 19.2.3.2 Associate Networks for European Research (RARE).- 19.3 Network protocols.- 19.3.1 KERMIT.- 19.3.2 Rechner Verbund System (RVS).- 19.3.3 TCP/IP Networking Protocol.- 19.4 Standards and specification work.- 19.4.1 File Transfer, Access and Management (FTAM).- 19.4.2 Message Handling System (MHS).- 19.4.3 Manufacturing Automation Protocol (MAP).- 19.4.4 Technical and Office Protocol (TOP).- 19.4.5 Communications Network for Manufacturing Applications (CNMA).- 19.4.6 Deutsches Forschungsnetz (DFN).- 19.4.7 Conformance Testing Services (CTS).- 19.4.8 Communication Architecture for Layered Open Systems (CARLOS).- 20. The CAD*I network.- 20.1 Established network connections.- 20.1.1 Bayerische Motorenwerke AG.- 20.1.2 Cranfield Institute of Technology.- 20.1.3 Danmarks Tekniske Højskole.- 20.1.4 Kernforschungszentrum Karlsruhe GmbH.- 20.2 File transfer test software “CADINE”.- 21. Results of the networking experiments.- 21.1 Networks.- 21.1.1 Public Data Networks.- 21.1.2 Local Area Networks.- 21.1.3 Academic and Research Networks.- 21.2 Network protocols.- 21.2.1 KERMIT.- 21.2.2 RVS (Rechner Verbund System).- 21.2.3 File Transfer based on FTAM.- 21.2.4 Message Handling System X.400.- 22. The CAD*I metafile utility.- 22.1 A future CAD data exchange environment based on FTAM.- 22.2 The application process.- 22.3 The application interface.- 22.3.1 The OSI environment.- 22.3.2 The real system environment.- 23. Summary of network investigations.- A New Specification Technique for CAD Models.- 24. Algebraic data types: a new approach to specifying CAD models.- 24.1 Introduction.- 24.2 Constructors, attributes, relations, modifiers.- 24.3 Introduction to important concepts of algebra.- 24.3.1 Object specifications.- 24.3.2 Algebraic specification for data base implementations.- 24.4 Algebraic specification for model conversion in CAD data exchange.- 24.5 A minimal geometric model specification example.- 24.5.1 Points and circle with HDSL.- 24.5.2 Points and circle with EXPRESS.- 24.5.3 Points and circle with ASN.1.- 24.5.4 Points and circle in an algebraic specification.- 24.6 Comparison of specification capabilities.- 24.7 Algebraic specification of CAD models.- References.- Appendix A. Three different types of standards.- A.1 Types of standards.- A.2 Introduction to function standards.- Appendix B. List of frequently used abbreviations.