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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
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