INTRODUCTION TO CADWhat is CAD?

–Integration of CS techniques in engineering design–Use of computers(hardware & software)for designing products

–Numerical method, optimizations etc.–2D/3D drafting–3D modeling for visualization–Modeling curves,surfaces,solids,mechanism,assemblies,etc.

• ANALYSIS– Stress (deflection analysis,I.e. numerical

methods,FEM– Simulation of actual use– Optimizations– Applications– CAD/CAM integration– Process planning

• DISPLAY VISULIAZITION AIDS– Display of model objects– Mapping objects onto screen coordinates– Surface display,shading– Projections– Hidden line removal when multiple

surfaces are displayed

REQUIREMENTS OF MODELING

• Solids are modeled by storing information of constituent surfaces

• This help in– Displaying surfaces(3D)– Computing solid properties– Modeling by storing info.on bounding

curves or by storing their geometric definitions

DATA BASES FOR CADVolume

Plane surfaces Warped surfaces

curves Net of curves patch

point

Is bounded by

Is boundary of

Consist of Belongs toBelongs to

Consist of surface unit

Has boundary curve

Is chain of Makes up

precedessucceeds

Has

end

poi

nt

Is th

e en

d of

Is th

e st

art o

f

Has

star

ting

poin

t

delimitssurface

Curve segment

LIST OF REFERENCE BOOKS• Principal of interactive CG by Newman &

sprawl*• Geometric modeling by Mortenson*• Fundamental of ICG by Foley & van dam• Procedural elements of CG by Rogers*• Mathematical elements of CG by Rogers and

Adams• Principal of CG by Hearn & baker• Computer graphics,A programming approach by

Steven & Harrington

• An introduction to FE computations by Hinton & Owen

• An introduction to FE in engineering* by Chandrupatla & Belegundu

• Zincowicz (3C)• Zincowicz & taylor (4C)

Evaluations

• Minors (I and II) – 30%• Major --- 40%• Labs ---- 20 %• Quizes --- 10%

DISPLAY DEVICES

• Storage tube devices• Permanent phosphorescence• For erasing entire screen is flooded with a

particular voltage• Can draw a line from any point to any point• CALLIGRAPHIC REFRESH GRAPHICS

DISPLAY• Picture is refreshed 40-50 times a second

• Display buffer & controller• Stores INFO about each entity to be displayed

Displaybuffer

Vector/character generator CRTcontroller

Repeats whole process 40-50 times a second

RASTER REFRESH GRAPHICS DISPLAY

• SCREEN IS A MATRIX OF POINTS

• Each point (pixel) can be bright/dark• Lines & curves as series of bright pixels

• Frame buffer stores a bit for each pixel(I if on, o if off)bit plane

• Additional bit planes for achieving different gray levels/colors.

• The programmer modifies the frame buffer• And the display controller refreshes the

screen on the basis of the frame buffer

INPUT OUTPUT DEVICES• Input devices

– Analog type:mouse (ball type)

–

X-y variable

Resistance

– Track ball– Joy stick

• Digital type• Light pen

– Light sensitive diode to point the screen– Positioned is sensed on basis of when pen

senses light

TABLET AND PEN

Pen emits radio frequency and intensity received by each wire tells the position

Grid of wire

HARDCOPY AND OUTPUT DEVICES

• Flat bed plotters– Pen– X-drive motor & Y-drive motor– Pen raise & lower mechanism– Controller

– Drum plotter• Pen• Raise and lower mechanism

• X-drive(for pen) & Y drive(for drum) motors• Controller• Printers

– DMP– Laser– Inkjet