Computer Aided Design2 ppt

8/7/2019 Computer Aided Design2 ppt

1/15

Computer Aided Design

GEOMETRIC MODELING USING

Interactive

M .Elango

Lecturer in Mechanical Engineering

Thiagarajar college of EngineeringMadurai

ICG


2/15

Types of Computer Graphics


3/15


4/15


5/15


6/15

A local area network - connected with CAD Workstation


7/15

7

Interactive Computer Graphics

User

Application

Screen

input

image


8/15

8

Representations in graphics

Vector Graphics

Image is represented by continuous geometric

objects: lines, curves, etc.

Raster Graphics

Image is represented as an rectangular grid ofcoloured squares


9/15

9

Representations in graphics

Vector Graphics

Image is represented by continuous geometric

objects: lines, curves, etc.

Raster Graphics

Image is represented as an rectangular grid ofcoloured squares


10/15

10

Vector graphics

Graphics objects: geometry + colour

Complexity ~ O(number of objects)

Geometric transformation possible withoutloss of information (zoom, rotate, )

Diagrams, schemes, ...

Examples: PowerPoint, CorelDraw, ...


11/15

11

Raster graphics

Generic

Image processing techniques

Geometric Transformation: loss of information

Complexity ~ O(number of pixels)

Jagged edges, anti-aliasing Realistic images, textures, ...

Examples: Paint, PhotoShop, ...


12/15

12

ConversionVector graphics

Pattern

Rasterization, recognition

Scan conversion

Rastergraphics


13/15

line-drawing algorithm

dx = x2 - x1

dy = y2 - y1forx from x1 to x2

{ y = y1 + (dy) * (x - x1)/(dx)

plot(x, y) }

It is assumed here that the points have already been ordered so that

x2 > x1. This algorithm works just fine when dx> = dy, but it is quite slow

on a digital computer, as it requires floating-point calculations. Ifdx abs(x1 - x0)

ifsteep then

swap(x0, y0)

swap(x1, y1)ifx0 > x1 then

swap(x0, x1)

swap(y0, y1)

intdeltax := x1 - x0

intdeltay := abs(y1 - y0)

realerror := 0realdeltaerr := deltay / deltax

intystep

inty := y0

ify0 < y1 then ystep := 1 else ystep := -1

forx from x0 to x1

ifsteep then plot(y,x) else plot(x,y)error := error + deltaerr

iferror 0.5 then

y := y + ystep

error := error - 1.0

*** Some Exercises On AutoCAD using Points and Line Command ****

Documents

Computer Aided Design2 ppt