Download - 3-D to Orthographic Projection - Dr. Mukesh
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Lecture 6
http://home.iitk.ac.in/~mukesh/
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PRACTICE
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PRACTICE
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3-D to Orthographic Projection
Orthographic Projection 3D
(i) Axonometric Isometric
(ii) Oblique
(iii)Perspective
Why do we need 3-D Pictorial Drawings?
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Parallel to Picture plane
(only one face seen)Rotated about vertical axis
(two faces seen)
Rotated about vertical & profi le
Axes (three faces seen)
Can get Infinite 3-d views needs uniformity and standardization
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R,U
R,S
S
T
SR
U
T
First Position one face seen
Rotate about Vertical axis by 450
Two faces seen
Then
Rotate about profile axis by 350(three faces seen)
Projections are still orthographicWhat these rotations have done?
SR, RU, RT all foreshortened but bequal lengths
Three mutually perpendicularEdges, SR, RU and RT nowmake equal angle of 120o
with each other and are called
ISOMETRIC AXES
S
R,U
T
S R
U
T
U
T
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Schematic presentation of concept
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30o30o
One Can draw isometric Figure with the help of Isometric box
Two types : (i) Isometric Projection Take lines as foreshortened(ii) Isometric drawing - Disregard foreshortening take actual length
Isometric
Axes
AB
Quiz:How much AB is foreshortened?
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A. Isometric projection: foreshortened (81/100)
B. Isometric drawing: No foreshortening (100/100)
No difference in shape - Isometric drawing larger inLinear proportion of 1.23:1.
Most common form is to use isometric drawing
A B
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Important
All lines parallel to isometric axes Isometric lines
All isometric lines are foreshortened equally (81/100)
All other non-isometric lines may or may not foreshorten
Foreshortening ratio of such lines may vary disproportionately
Projections of parallel lines are parallel.
All measurements can only be marked on isometric lines
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Make Isometric scale : foreshortened to 81/100 to
Be used in Isometric projection
0
0
1
2
3
4
1
2
3
4 450
300
Reg
ular
Scale
Isom
etric
Scale
ISOMETRIC SCALE
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20
12
10
20
10
12
A
B
C
Decide width and depth directions height direction is f ixed.
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AB
C
D
A
B
C
D
Boxing Method
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Now start drawingIsometric
Front
Top
Right Side
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Identify hidden lines
Now erase the hidden linesFront
Top
Right Side
300300
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Now erase hidden portion of ellipse Front
Top
Right Side
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Isometric Front
Top
Right Side
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Now start drawingIsometric
Front
Top
Right Side
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Identify hidden lines and erase
Draw base as in previous isometric
Now draw the additional surface
Smoothly join both ellipses Front
Top
Right Side
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Isometric Front
Top
Right Side
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56
20
40
56
49
98
FRONT
TOP
RIGHT SIDE
L3 - 3.1
32
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56
20
40
56
49
98
FRONT
TOP
RIGHT SIDE
L3 - 3.1
32
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56
20
40
56
49
98
FRONT
TOP
RIGHT SIDE
L3 - 3.1
32