7e300 [auto]cad basics: foundations and 2d drawings 7e300 international ca(a)d-course
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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● 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● 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)[email protected]
● 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