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Lost in TranslationTechnological Views on Preserving CAD

Alex Ball

DCC/UKOLN, University of Bath

15 August 2014

Except where otherwise stated, this work is licensed underthe Creative Commons Attribution 4.0 International licence:http://creativecommons.org/licenses/by/4.0/

Supported by

ARCHIVES*RECORDS 2014, Washington, DC 2014-08-15

http://creativecommons.org/licenses/by/4.0/

Outline

Introduction

3D geometric representations

Advanced modelling techniques

Use cases

Possible solutions


Introduction


Key message

The main technological barrier to preserving CAD isvarietyÉ of 3D geometric representationsÉ of advanced modelling techniquesÉ of use cases


3D geometric representations


Wire-frame modelling


Surface modelling

Extruding Sweeping Lofting

Revolving Triangular mesh NURBS

cba

Gre

gA

L


http://en.wikipedia.org/wiki/File:NURBS_3-D_surface.gif

Constructive Solid Geometry

+ =


Boundary representation

=


Mistranslation and misinterpretation

c© Jianchang Qi, Vadim Shapiro


http://dx.doi.org/10.1115/1.2218367

Modelling techniques: summary

É There are many incompatible ways of modelling3D geometry.

É There are many incompatible ways ofinterpreting 3D models.


Construction history modelling

1. Insert cylinder l = 20 r = 1.0

Change cylinder l = 40 r = 0.5

2. Insert sprocket r = 3.0

3. Fit sprocket to cylinder

4. Group cylinder and sprocket

5. Scale group by 1.75×. . .


Procedural modelling

c© Yoav I. H. Parish & Pascal Müller

c© Barbara M. Cutler


http://dx.doi.org/10.1145/218380.218405http://people.csail.mit.edu/bmcutler/PROJECTS/PHD/

Parametric modelling

8 cm

28 cm

8 cm

18 cm


Feature-based modelling

RibsCavities



É CAD models contain much more than justgeometry.

É The geometry might be useless without theextra information.


Use cases


Reusing standard parts

c© Koray Pekericli

top-level assembly

part f

subassembly a

part a part b part c

subassembly b

part d part e part f

part j

subassembly c

part d part e part g

subassembly d

part a part h part i


Relationship with other documents

CADModel

ArchaeologyDatabase

Bill ofMaterials

ProcessModel

RationaleModel

SystemsModels

. . .


Integration with other systems

CADSystem

CAMSystem

FiniteElementAnalysisSystem

GeographicInformation

System

AnimationSystem

HighQuality

Renderer

. . .


Use cases

É You might need to coordinate CAD models withmany other types of information.

É You might need to mimic whole systems.


Possible solutions


Standards: IGES

2D drawing

Wire-frames

Surface modelling

Constructivesolid geometry

Boundaryrepresentation

IGES(ANSI Y14.26M-1981, . . .

ANS US/PRO/IPO-100-1996)

WunderCAD CAD-

ulous


Standards: STEP

STEPISO 10303?


Standards: STEP

STEPISO 10303!

LOTAR(NAS 9300/EN 9300)


Standards for BIM, CAD style conventions

BIMÉ ISO 16739:2013 Industry Foundation Classes (IFC) for data

sharing in the construction and facility management industriesÉ National BIM Standard – United States (NBIMS-US)É AEC (UK) BIM ProtocolÉ (BSI) PAS 1192-2 Information management for the

capital/delivery phase of construction projects

CAD styleÉ United States National CAD StandardÉ AEC (UK) CAD Standards For Layer Naming


Recommendations

É Establish why a CAD model will be kept, then target therequired properties for preservation.

É Create tests that can prove whether these properties havesurvived.

É Keep native CAD models for as long as they can be read.É Normalise to STEP/IFC and a geometry-only standard (or two).É Don’t forget supporting documentation, especially local

conventions and ‘house style’.É Campaign for better support for standard formats in CAD

systems!


DPC Technology Watch Report

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PreservingComputer-AidedDesign (CAD)

DPC Technology Watch Report 13-02 April 2013

Alex Ball

http://dx.doi.org/10.7207/twr13-02


http://dx.doi.org/10.7207/twr13-02

because good research needs good data

Thank you for your attention

DCC Website: http://www.dcc.ac.uk/

‘Preserving CAD’ report:http://dx.doi.org/10.7207/twr13-02


http://www.dcc.ac.uk/http://dx.doi.org/10.7207/twr13-02

Introduction3D geometric representationsAdvanced modelling techniquesUse casesPossible solutions

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