1. [Auto]CAD Basics: Foundations and 2D drawings
7E300 International CA(A)D-course

2. Overview 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

3. Overview continued Construction methods Manipulation methods Printing
Getting help

4. Overview continued 2nd lecture (Friday): 3D geometry types
‘Intelligent’ composite Objects
Architectural objects and helpers
Dimensioning
Printing
Rendering
Export

5. Goals 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

6. 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

7. 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

8. 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

9. 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?

10. 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

11. 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

12. CAAD applications in the architectural domain
Marketshare CAAD-packages (Germany 2003) according to online survey on

13. 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

14. CA(A)D by example: AutoCAD & ADT
System Architecture (very simplified)
End User
ADT UI
Visualization OpenGL / D3D
Standard AutoCAD UI
API (C/C++, LISP, VB etc.)
Geometry Kernel
Operating System

15. Elemental Computer Graphics
Coordinate Systems
Almost all CAD-applications based on three- dimensional Cartesian system with right-hand orientation
Image source:
Image source:

16. 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)

17. 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

18. Elemental Computer Graphics
Basic transformations
Translate (move)
Rotate
Scale

19. Basic geometry Translation
Absolute: Set coordinates directly in current coordinate system Example: Move absolute 5,1 (ACAD: move:5,1)

20. Basic geometry Translation
Relative: Set coordinates relative to current location in current coordinate system Example: Translate relative 5,1 (ACAD

21. Basic geometry
Rotation
Centered to object

22. Basic geometry
Rotation
Off-center rotation

23. Basic geometry
Scale
Uniform scale Example: Factor 0.5 and 2

24. Basic geometry
Scale
Non-Uniform scale (Achieved by ‘Stretch’ command in ACAD or by scaling blocks)

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

26. Geometric primitives Line
Elemental type used to assemble other geometry types
Composed geometry (rectangle etc.) can be broken down to lines

27. Geometric 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

28. Geometric primitives Circle
May often be constructed in many different ways:
Radius
Diameter
3 Points
2 Tangents & radius
etc

29. Geometric primitives Arc Fraction of circle:
Can be used to construct complex curved shapes by composition

30. Geometric primitives Parametric curves: Bézier spline
Historically eldest of the free-form curves with some limitations
Control vertices, control polygon

31. Geometric primitives Parametric curves: B-spline
Better control over curve
Found in many applications

32. Geometric primitives Parametric curves: NURBS
Non Uniform Rational B-Spline
Used by Autocad, most flexible
X,Y,Z,W coordinates for control points

33. Geometric primitives Pattern, hatches, fillings
Can only by applied to closed shapes (‘regions’ in ACAD, sort of 2D solids (more later on))

34. Geometric primitives Pattern, hatches, fillings (continued)
Modern applications offer associative fillings

35. Basic operations
Copy
Creates one or more copies of a geometry or groups
Definition of base point can be used for proper placement

36. Basic operations Array copy
Multiple copies in rectangular or polar (rotated) series

37. Basic operations
Mirror
Mirror using a mirror axis

38. Basic operations
Extend
Extend lines to arbitrary boundaries

39. Basic operations
Trim
Use arbitrary boundaries to cut away geometry

40. Basic operations Break
Use two arbitrary boundaries to cut away geometry in-between

41. Basic operations Stretch
Lengthen/shorten/scale/distort parts of geometries with some parts staying fixed

42. 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, .3 relative to last

43. Coordinate entry ACAD
Angular data entry: [Direction] < [Distance] Example: 5 units long line pointing to right in default WCS: 90<5.0

44. 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

45. 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

46. 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

47. 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)

48. 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

49. 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

50. Structuring drawings Blocks / groups
Complete parts made easily available for reuse
Manipulate complex parts applying modifications only to on object

51. Structuring drawings Layers
Easy metaphor for architects (stacked transparent paper)
Easy to handle
Unlimited granularity

52. 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

53. 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

54. 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

55. 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

56. Assignment 1
Turn in on by either creating a webpage and notify me or directly send to (please zip files)
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

57. Assignment 1 Please check
es/CAD_international/
Frequently. You will find material, assignments and schedule updates here.