Computer graphics

1. COMPUTER AIDED DESIGN

2. UNIT 1
FUNDAMENTALS OF COMPUTER
GRAPHICS

3. SYALLABUS
Product cycle
Design process
Sequential and concurrent engineering
Computer aided design – CAD system architecture
Computer graphics – co-ordinate systems- 2D and 3D transformations -
homogeneous coordinates
Line drawing -Clipping- viewing transformation

4. Product cycle
The cycle through which a product goes from development to
retirement is called product life cycle.
The product cycle starts with developing the product concept,
evolving the design, engineering the product, manufacturing the
part, marketing and servicing.
The product undergoes the following two main processes
Design process
Manufacturing process

6. DESIGN PROCESS
Design is an activity that needs to be well organized and should take into
account all influences that are likely to be responsible for the success of the
product under development.
The following models are considered in design purpose
Shigley
Pahl and Beitz
Ohsuga
Earle

7. Shigley design Process
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8. Pahl and Beitz design
Process
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9. Ohsuga design Process
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10. Earle design Process
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11. MORPHOLOGY OF DESIGN
Morphology design refers to the study of the chronological structure of
design projects.
It is defined by seven phases and their sub steps. Out of seven phases, the
first three phases belong to the design the proposed by asimow and the
remaining four phases belong to production, distribution, consumption and
retirement.

13. SEQUENCIAL ENGINEERING
Three major phases of conventional manufacturing process are design,
process planning and manufacturing.
All these phases are sequentially carried out.

15. CONCURRENT ENGINEERING
It is the methodology of restructuring the product development activity in
a manufacturing organization using cross functional team approach.

17. COMPARISION BETWEEN SEQUENTIAL
AND CONCURRENT ENGINEERING
Product development cost
Number of design changes
Lead time for product development
Customer satisfaction
Coordination between departments

20. COMPUTER AIDED DESIGN
Groover and Zimmers defined “CAD is the technology concerned with the use
of computer systems to assist the creation, modification, analysis and
optimization of a design”.

21. Roles of CAD in Design
Accurately generated and easily modifiable graphical representation of the
product.
User can nearly view the actual product on the screen, make any
modification to it and present his ideas on screen without any prototype,
especially during the early stages of the design process.
Complex design analysis in short time. By implementing Finite Element
Analysis (FEA) methods user can perform as follows
Static, dynamic & natural frequency analysis
Heat transfer analysis
Fluid flow analysis
Plastic analysis

22. Roles of CAD in Design
It records and recalls information with consistency and speed
Use of Product Data Management (PDM) systems can store the whole
design and processing history of a certain product for future reuse and
upgrade.

23. CAD PROCESS

24. APPLICATION OF CAD
Mechanical engineering
Civil engineering
Electrical and electronics engineering
Textile industry

25. ADVANTAGES OF CAD
Easy editing
High quality
Compact storage
3D Drawing

26. CAD SYSTEM ARCHITECTURE
It is an early model which was used for the basic geometry construction
and modelling purpose.
Four major components of CAD System Architecture are
1. Database
2. Operating system
3. Input/output devices
4. User interface

29. COMPUTER GRAPHICS (CG)
Computer graphics is a technology which uses the display of the drawing or
the geometric model of the component in CAD.
CG may be defined as the process of creation, storage and manipulation of
drawings and pictures with aid of a computer.
It is an extremely effective medium for communication between users and
computers.
There are two types
1. Passive CG
2. Interactive CG

31. Interactive CG
The following functions of the ICG
Modelling
Storage
Manipulation
Viewing

32. ADVANTAGES OF COMPUTER
GRAPHICS
The object drawings can be denoted by its geometric model in three
dimensions. i.e. X, Y, Z coordinates.
Accurate drawings can be made.
Sectional drawings can be easily created.
Modification of geometric model of objects is easy.
It is easy storage and retrieval of drawings.

33. APPLICATIONS OF COMPUTER
GRAPHICS
Paint programs
Design programs
Presentation graphics software
Animation software
CAD software
Desktop publishing
Education and training
Image processing

34. CO-ORDINATE SYSTEMS
In general, there are two types of co-ordinate system
1. Cartesian – Linear distances X,Y and Z
2. Polar – Angles such as θ, α, φ

35. Left hand and right hand co-ordinate systems
Multiple co-ordinate systems
World co-ordinate system
Object co-ordinate system
Hierarchical co-ordinate system
View point co-ordinate system
Model view co-ordinate system
Screen co-ordinate system
View port co-ordinate system

36. Left and right handed
coordinate system
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37. 2D & 3D
(GEOMETRIC)TRANSFORMATION
A geometric transformation is an operation that modifies
its shape, size, position, orientation etc. with respect to its
current configuration operating on the vertices.
Some of the important transformations are
Translation
Scaling
Rotation
Reflection
Shear
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38. 2D & 3D TRASLATION
,
, ,
x y
x
y
x x t y y t
tx x
ty y
    
     
            
  
P P T
P P T
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2D FORMULA 3D FORMULA

39. 2D & 3D SCALING
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2D FORMULA 3D FORMULA
,
0
0
x y
x
y
x x s y y s
sx x
sy y
    
     
         
  P S P

40. 2D & 3D ROTATION
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2D FORMULA 3D FORMULA

41. HOMOGENEOUS TRANSFORMATION
The three dimensional representation of two
dimensional plane is called as homogeneous
representation and the transformation using
homogeneous representation is called
homogeneous transformation.
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42. HOMOGENEOUS TRANSFORMATION
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43. LINE DRAWING
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Straight line segments are used a great deal in computer generated
pictures. The following criteria have been stipulated for line drawing
displays:
i. Lines should appear straight
ii.Lines should terminate accurately
iii.Lines should have constant density
iv.Line density should be independent of length and angle
v.Line should be drawn rapidly

44. DDA ALGORITHM
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A popular method uses an algorithm known as “Digital Differential
Analyzer” which generates lines from their differential equations.
For a line segment joining two points P1 and P2, a parametric
representation is given by
P(u) =P1+(P2-P1)u
In terms of x(u) and y(u)
x(u) = x1 + (x2-x1)u
y(u) = y1 + (y2-y1)u

45. BRESENHAM’S LINE ALGORITHM
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The basic principle of Bresenham’s line algorithms is to select the optimum
raster location to represents a straight line.
To achieve optimum raster scan, the algorithm always increments either x
or y by one unit depending on the slope line.
The increment in the other variable is determined by examining the
distance between the actual line location and the nearest pixel.
This distance is called decision variable or error.

46. CLIPPING
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If any part of the geometry is not inside the window, it is made invisible by
the graphic software is called clipping.

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49. VIEWING TRANSFORMATIONS
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Displaying an image of a picture involves in mapping the co-ordinates of the
picture into the appropriate coordinates on the device where the image is to
be displayed.

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