7E300

[Auto]CAD Basics:Foundations and

2D drawings

7E300 International CA(A)D-course www.ds.arch.tue.nl/education/courses/CAD_International/

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OverviewOverview● Introduction to CA(A)D-Packages:

– The promise

– The real world

● CA(A)D by Example: AutoCAD & ADT

– History

– System architecture

● Basic Geometry

– Coordinate systems

– Basic transformations

– Geometric primitives

● Construction aids

– Manual entry

– Snaps

– Alignments

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Overview continuedOverview continued● Construction methods● Manipulation methods● Printing● Getting help

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Overview continuedOverview continued2nd lecture (Friday):● 3D geometry types● ‘Intelligent’ composite Objects● Architectural objects and helpers● Dimensioning● Printing● Rendering ● Export

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GoalsGoals

● Give an overview of the topics involved

● Give introduction to most basic modeling/drawing techniques

● Give advise for self-study● Give introduction to AutoCAD/ADT

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Building model paradigmBuilding model paradigm

● Building is designed assembling different objects

● Every object of the building has a set of properties that can be interpreted in different contexts

● Geometrical representations (i.e. drawings) are only one of many aspects. Drawings can be generated dynamically from existing data

● Different domains (structural engineering, building physics etc.) have different views on building model

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Building model paradigmBuilding model paradigm

● Advantages– ‘intelligent’ applications can gather

all sorts of data (room sizes, material lists etc.) from a well defined model

– Dependent drawings such as sections do not have to be redrawn on changes but automatically adapt

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Building model paradigmBuilding model paradigm

● Problems– Additional (non-graphical)

information has to be provided by architect

– Coherency when changing objects – Object relations have to be designed – Complexity with all data required

often cannot not be generated at design time

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Future developmentsFuture developments

● Architect as ‘building programmer’?

● Advanced input techniques– Virtual/Augmented reality– ‘Intelligent’ recognition handmade

drawings– Voice recognition– Reuse of design strategies

● Better compatibility through open standards (IFC etc.)

● Finally: Paperless office at last?

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Introduction to CA(A)D packages

Introduction to CA(A)D packages

● The promises:– Let repetitive work be done by the machine– Draw more exactly– Draw quicker– Concentrate on the building instead of the

drawing– Let drawings be generated from a n-

dimensional building model– Get rid of paper by electronic documents– Accelerate cooperative work in the whole

building cycle by reusing documents under domain-specific aspects

– Let ‘intelligent’ functionality take care of easy tasks

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Introduction to CA(A)D packages

Introduction to CA(A)D packages

● The real world:– CA(A)D in most cases used as 2D

pen and paper– Additional information required for

building model seldom provided by architect

– Document exchange critical due to lack of standards

– Applications not error-prone – Functionality for architecture

domain limited

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CAAD applications in the architectural domain

CAAD applications in the architectural domain

Marketshare CA(A)D

AutoCAD / ADT

ArchiCAD

SPIRIT

Nemetschek Allplan

Microstation

Vectorworks

ARRIBA / RIBCON

Other

Marketshare CAAD-packages (Germany 2003) according to online survey on www.aecweb.de

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CA(A)D by example: AutoCAD & ADT

CA(A)D by example: AutoCAD & ADT

● History:– 1960 Ivan Sutherland SKETCHPAD– 1982 AutoCAD 1.0 introduced on COMDEX– 1985 AutoCAD 2.1 (R 6) goes 3D– 1986 AutoLISP– 1992 R 12 with new Solid kernel &

rendering – 1993 R 12 goes Windows– 1997 R 14 most important version ever– 1998 ADT on R 14– 2000 AutoCAD 2000

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VisualizationOpenGL / D3D

CA(A)D by example: AutoCAD & ADT

CA(A)D by example: AutoCAD & ADT

● System Architecture (very simplified)

Operating System

Geometry Kernel

ADT UIStandard AutoCAD UI

API (C/C++, LISP, VB etc.)

End User

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Elemental Computer Graphics

Elemental Computer Graphics

● Coordinate Systems– Almost all CAD-applications based on

three-dimensional Cartesian system with right-hand orientation

Image source: http://www.vard.org/mono/gait/soutas.htm Image source: http://en.wikipedia.org/wiki/Cartesian_coordinate_system

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Elemental Computer Graphics

Elemental Computer Graphics

● Coordinate Systems can be modified– Global: for the entire scene/’world’

(WCS in ACAD)– Local to an object / arbitrarily chosen

by user (UCS in ACAD)Global (WCS)

Local (UCS)

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Elemental Computer Graphics

Elemental Computer Graphics

● Units – Internal units and precision fixed and

limited by machine and application– Real-world units (m, mm, ft, inches) can

be applied arbitrarily suiting own needs– Be careful when exchanging data!– Choice of units affects dimensioning,

text, hatches and line weights in ACAD!– Although units can be changed later,

conversion problems esp. apply to switch between metric/imperial

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Elemental Computer Graphics

Elemental Computer Graphics

● Basic transformations – Translate (move)– Rotate– Scale

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Basic geometryBasic geometry● Translation

– Absolute: Set coordinates directly in current coordinate systemExample:Move absolute 5,1(ACAD: move:5,1)

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Basic geometryBasic geometry● Translation

– Relative: Set coordinates relative to current location in current coordinate systemExample: Translate relative 5,1(ACAD move:@5,1)

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Basic geometryBasic geometry● Rotation

– Centered to object

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Basic geometryBasic geometry● Rotation

– Off-center rotation

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Basic geometryBasic geometry● Scale

– Uniform scaleExample: Factor 0.5 and 2

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Basic geometryBasic geometry● Scale

– Non-Uniform scale

(Achieved by ‘Stretch’ command in ACAD or by scaling blocks)

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Geometric primitivesGeometric primitives

● Geometric primitives 2D– Point (Vertex)– Elemental type for all other geometry– Often used as construction aid

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Geometric primitivesGeometric primitives

● Line– Elemental type used to assemble other

geometry types– Composed geometry (rectangle etc.)

can be broken down to lines

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Geometric primitivesGeometric primitives

● Conic sections– Circles, arcs, ellipses, parabolas and

hyperbolas are composed of conic sections

– Granularity may be important for printing

Image-source: Mathworld.Wolfram.com

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Geometric primitivesGeometric primitives

● Circle– May often be constructed in many

different ways:● Radius● Diameter● 3 Points● 2 Tangents & radius● etc

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Geometric primitivesGeometric primitives

● Arc– Fraction of circle:

● Can be used to construct complex curvedshapes by composition

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Geometric primitivesGeometric primitives● Parametric curves: Bézier spline

– Historically eldest of the free-form curves with some limitations

– Control vertices, control polygon

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Geometric primitivesGeometric primitives● Parametric curves: B-spline

– Better control over curve– Found in many applications

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Geometric primitivesGeometric primitives● Parametric curves: NURBS

– Non Uniform Rational B-Spline– Used by Autocad, most flexible– X,Y,Z,W coordinates for control points

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Geometric primitivesGeometric primitives● Pattern, hatches, fillings

– Can only by applied to closed shapes (‘regions’ in ACAD, sort of 2D solids (more later on))

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Geometric primitivesGeometric primitives● Pattern, hatches, fillings

(continued)– Modern applications offer associative

fillings

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Basic operationsBasic operations● Copy

– Creates one or more copies of a geometry or groups

– Definition of base point can be used for proper placement

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Basic operationsBasic operations● Array copy

– Multiple copies in rectangular or polar (rotated) series

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Basic operationsBasic operations● Mirror

– Mirror using a mirror axis

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Basic operationsBasic operations● Extend

– Extend lines to arbitrary boundaries

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Basic operationsBasic operations● Trim

– Use arbitrary boundaries to cut away geometry

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Basic operationsBasic operations● Break

– Use two arbitrary boundaries to cut away geometry in-between

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Basic operationsBasic operations● Stretch

– Lengthen/shorten/scale/distort parts of geometries with some parts staying fixed

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Coordinate entry ACADCoordinate entry ACAD● Directly enter coordinates into the

WCS or current UCS by a comma-separated list with arbitrary precision

● Examples for single points/vertices:1, 2.0, .3relative to last point: @1,2,3.01

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Coordinate entry ACADCoordinate entry ACAD● Angular data entry:

[Direction] < [Distance]Example: 5 units long line pointing to right in default WCS:90<5.0

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Operation and selectionOperation and selection● Order of operation in ACAD

– Most command can either be invoked ● Verb – object (state operation first and

select objects to apply it to later on)● Object – verb (Select objects and state

which operation to carry out)– The default method (if no other

command explicitly invoked) in ACAD always is set to selection

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Operation and selectionOperation and selection● Selection in ACAD

– Objects can be selected by ● Pick single objects in succession (picking

them again de-selects them● Drag rectangle from up-left to down right

to select all objects inside rectangle● Drag rectangle form down-right to up-left

to select those that are either inside or touched by selection rectangle

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Operation and selectionOperation and selection● ‘Transparent’ operations

– While in the middle of a command sequence, the current command can be suspended for later finish in order to carry out in-between steps

– Most typical examples are the different viewing command (zoom, pan, change perspective etc)

– On the command line transparent mode of a command is activated by putting a ‘ in front of the command statement

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Visual assistanceVisual assistance● Ortho mode: only rectangular

movements of mouse possible● Snapping: Catch i.e. one of the following

points of existing geometry:– Endpoint– Midpoint– Center– Tangent– Perpendicular– Nearest (point on line/curve)

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Visual assistanceVisual assistance● OSnap tracking:

Visual indication of graphic cursor such as – Parallel to existing line– Apparent intersection of two lines– Point on virtual extension of existing line

● Grid: Virtual points in drawing space. When put into exclusive Grid-snap mode only these point can be chosen with the pointing device to construct geometry

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Structuring drawingsStructuring drawings

● Color / Line weight / Linetype– Historical method– Limited to specific set of colors in

most applications– Might interfere with output needs– Colors not always distinguishable

very well

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Structuring drawingsStructuring drawings

● Blocks / groups– Complete parts made easily available

for reuse– Manipulate complex parts applying

modifications only to on object

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Structuring drawingsStructuring drawings

● Layers– Easy metaphor for architects

(stacked transparent paper)– Easy to handle– Unlimited granularity

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Structuring drawingsStructuring drawings

● XRefs / inclusions– Drawing split into smaller

entities/files which are composed into a single drawing

– Especially well-suited for group work (different members may simultaneously work on different parts of the building in different files

– Often problematic when moving to other machines / working environments

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Standard exchange formats

Standard exchange formats

● DWG– Proprietary Autodesk format with

frequent changes– Can be im-/exported by many

applications– Features advanced geometry (Solids

etc.) – Can be extended by 3rd party

applications

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Standard exchange formats

Standard exchange formats

● DXF– Most established, open standard for

data exchange to date, interfaces build into many applications

– Human readable ASCII format– Limited set of geometry and

information – Only faces/polygons supported – No advanced geometry such as

solids and NURBS

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Standard exchange formats

Standard exchange formats

● IFC– Developed to suit needs of building

industry– Open– Extendable– Lots of advanced meta-data storable– Not widely supported (yet/anymore)– Under development / constant change– XML-version human readable and easy

to integrate for collaboration with other applications

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Assignment 1Assignment 1

● Turn in on 21.03.04 by either creating a webpage and notify me or directly send to (please zip files)j.beetz@bwk.tue.nl

● Please document your work progress and hand in questions that will be answered in class on Friday

● If need support also available on ICQ/Yahoo

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Assignment 1Assignment 1

Please check

http://www.ds.arch.tue.nl/education/courses/CAD_international/

Frequently. You will find material, assignments and schedule updates here.