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[Auto]CAD Basics: Foundations and 2D drawings. 7E300 International CA(A)D-course Overview. Introduction to CA(A)D-Packages: The promise The real world CA(A)D by Example: AutoCAD & ADT History System architecture Basic Geometry

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[Auto]CAD Basics:

Foundations and

2D drawings

7E300 International CA(A)D-course

  • 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
overview continued
Overview continued
  • Construction methods
  • Manipulation methods
  • Printing
  • Getting help
overview continued1
Overview continued

2nd lecture (Friday):

  • 3D geometry types
  • ‘Intelligent’ composite Objects
  • Architectural objects and helpers
  • Dimensioning
  • Printing
  • Rendering
  • Export
  • 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
building model paradigm
Building 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
building model paradigm1
Building 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
building model paradigm2
Building 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
future developments
Future 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?
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
introduction to ca a d packages1
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
caad applications in the architectural domain
CAAD applications in the architectural domain

Marketshare CAAD-packages (Germany 2003) according to online survey on

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
ca a d by example autocad adt1
CA(A)D by example: AutoCAD & ADT
  • System Architecture (very simplified)

End User


VisualizationOpenGL / D3D

Standard AutoCAD UI

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

Geometry Kernel

Operating System

elemental computer graphics
Elemental Computer Graphics
  • Coordinate Systems
    • Almost all CAD-applications based on three-dimensional Cartesian system with right-hand orientation

Image source:

Image source:

elemental computer graphics1
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)

elemental computer graphics2
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
elemental computer graphics3
Elemental Computer Graphics
  • Basic transformations
    • Translate (move)
    • Rotate
    • Scale
basic geometry
Basic geometry
  • Translation
    • Absolute: Set coordinates directly in current coordinate systemExample:Move absolute 5,1(ACAD: move:5,1)
basic geometry1
Basic geometry
  • Translation
    • Relative: Set coordinates relative to current location in current coordinate systemExample: Translate relative5,1(ACAD move:@5,1)
basic geometry2
Basic geometry
  • Rotation
    • Centered to object
basic geometry3
Basic geometry
  • Rotation
    • Off-center rotation
basic geometry4
Basic geometry
  • Scale
    • Uniform scaleExample: Factor 0.5 and 2
basic geometry5
Basic geometry
  • Scale
    • Non-Uniform scale(Achieved by ‘Stretch’ command in ACAD or by scaling blocks)
geometric primitives
Geometric primitives
  • Geometric primitives 2D
    • Point (Vertex)
    • Elemental type for all other geometry
    • Often used as construction aid
geometric primitives1
Geometric primitives
  • Line
    • Elemental type used to assemble other geometry types
    • Composed geometry (rectangle etc.) can be broken down to lines
geometric primitives2
Geometric primitives
  • Conic sections
    • Circles, arcs, ellipses, parabolas and hyperbolas are composed of conic sections
    • Granularity may be important for printing


geometric primitives3
Geometric primitives
  • Circle
    • May often be constructed in many different ways:
      • Radius
      • Diameter
      • 3 Points
      • 2 Tangents & radius
      • etc
geometric primitives4
Geometric primitives
  • Arc
    • Fraction of circle:
      • Can be used to construct complex curvedshapes by composition
geometric primitives5
Geometric primitives
  • Parametric curves: Bézier spline
    • Historically eldest of the free-form curves with some limitations
    • Control vertices, control polygon
geometric primitives6
Geometric primitives
  • Parametric curves: B-spline
    • Better control over curve
    • Found in many applications
geometric primitives7
Geometric primitives
  • Parametric curves: NURBS
    • Non Uniform Rational B-Spline
    • Used by Autocad, most flexible
    • X,Y,Z,W coordinates for control points
geometric primitives8
Geometric primitives
  • Pattern, hatches, fillings
    • Can only by applied to closed shapes (‘regions’ in ACAD, sort of 2D solids (more later on))
geometric primitives9
Geometric primitives
  • Pattern, hatches, fillings (continued)
    • Modern applications offer associative fillings
basic operations
Basic operations
  • Copy
    • Creates one or more copies of a geometry or groups
    • Definition of base point can be used for proper placement
basic operations1
Basic operations
  • Array copy
    • Multiple copies in rectangular or polar (rotated) series
basic operations2
Basic operations
  • Mirror
    • Mirror using a mirror axis
basic operations3
Basic operations
  • Extend
    • Extend lines to arbitrary boundaries
basic operations4
Basic operations
  • Trim
    • Use arbitrary boundaries to cut away geometry
basic operations5
Basic operations
  • Break
    • Use two arbitrary boundaries to cut away geometry in-between
basic operations6
Basic operations
  • Stretch
    • Lengthen/shorten/scale/distort parts of geometries with some parts staying fixed
coordinate entry acad
Coordinate 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
coordinate entry acad1
Coordinate entry ACAD
  • Angular data entry:[Direction] < [Distance]Example: 5 units long line pointing to right in default WCS:90<5.0
operation and selection
Operation 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
operation and selection1
Operation 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
operation and selection2
Operation 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
visual assistance
Visual 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)
visual assistance1
Visual 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
structuring drawings
Structuring 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
structuring drawings1
Structuring drawings
  • Blocks / groups
    • Complete parts made easily available for reuse
    • Manipulate complex parts applying modifications only to on object
structuring drawings2
Structuring drawings
  • Layers
    • Easy metaphor for architects (stacked transparent paper)
    • Easy to handle
    • Unlimited granularity
structuring drawings3
Structuring 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
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
standard exchange formats1
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
standard exchange formats2
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
assignment 1
Assignment 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
assignment 11
Assignment 1

Please check

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