ENGR1170 CHAP 5
MULTIVIEW SKETCHING
Objectives
1. Explain orthographic and multiview projections
2. Identify Frontal, horizontal and profile planes
3. Identify the six principal views and the three
space dimensions
4. Apply standard line practices to multiview
drawings
5. Create a multiview drawing by sketching
Projection Theory
• Parallel
– Object be positioned at infinity and viewed from
multiple points on an imaginary line parallel to object
• Perspective
– Object positioned at a finite distance and
viewed from a single point
Projection Theory
• All Projection theory is based on two
variables:
– Line of sight
• An imaginary ray of light between an observers eye
and a single point
– Plane of Projection
• An imaginary flat plane upon which the image
created by the lines of sight is projected
?
Orthographic Projection
• Is a parallel projection technique in which the
plane of projection is positioned between the
observer and the object and is perpendicular to the
lines of sight
• Can show all three dimensions in one view
• Or multiviews that show only two
dimensions in a single view
Multiview
• Multiview: More than one view is necessary
to completely define 3D object
• Each view shows two of the three principal
directions
Surfaces
Three Space Dimensions
•Horizontal
distance in front view: width
• Vertical dimension in the front view: height
• Any view from a viewpoint that is 900 from
that of the front view plane: depth
Standard Arrangement of Views
• Why standard?
– Easy interpretation, consistency
• Front view usually central and shows the
objects shape most clearly
• Top view always aligned above the front
view
• Right side view placed directly to the right
of the front view
Producing a Multiview Sketch
z
Select Front View
z
Align View Bounding Boxes
z
Sketch Features
– True Shapes Remain
– Project Between Views
– Label Vertices if Needed
Select Front View
• Universally Used -- Clock Face
• Shows Most Characteristic Shape -- the
“U” shape of a horse shoe.
• Generates Fewest
Number of Hidden Lines
for Entire Drawing
Align View Bounding Boxes
DEPTH
WIDTH
TOP
DEPTH
Miter line at 45°
HEIGHT
HEIGHT
WIDTH
FRONT
RIGHT
Sketch Features – View Projection
TOP
Miter line at 45°
FRONT
RIGHT
C
Labeling
Vertices
A
B
C
A
B C
C
A
B
B, A
Six Principal Views
Multiview and Isometric Pictorials
What’s new?
Multiview Characteristics
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•
•
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multi-view
true shapes
orientation
1st vs. 3rd angle
bounding boxes
constr. lines to
project/transfer
features
miter line
hidden lines
center/symmetry
lines
line precedence
Linetype Standards
(ASME Y14.2M-1992)
(≈ ½ of thick line)
Precedence of lines:
Visible Lines > Hidden Lines > Centerlines
Centerline Conventions
• to show
circle/arc
center or axis
of symmetry
• long lines
separated by
dash and two
gaps
• dashes
commonly ≈
1/8” long
Hidden Line Conventions
• evenly
spaced
dashes
• spaces ≈
1/2 of dash
length
• dashes
commonly
≈ 1/8” long
Multiview Line Types
?
?
?
?
?
Other views
• The six views show essentially the same
information as three
• Which views are redundant?
• Sometimes additional views will be offered
to clarify complex features
Projection Planes (Third Angle)
• We can regard the orthographic views as
projections unto a glass box
Three Primary Views (Third Angle)
• We can unfold the box to produce the arrangement
of views (US, Canada, a few others)
• Europe, Asia, use first-angle projection
First Angle Projection
• Front view is projected onto a plane of
projection behind the front view
• Right side view projected unto a viewing
plane to the left of the object
• Plan view view projected unto a viewing
plane below object
Projection Planes ( First Angle ? )
WRONG! Top View should be beneath Front
Symbol Added to Drawing
third angle
first angle
Third- and First-Angle Projection
United States
Europe
1st vs 3rd Angle Multiview
House Elevations (North, East etc.)
One View Sketches
3
1
Missing Line #1
Missing Line #2
Assignment
• In Chapter 5 read:Section 5.1-5.7
• Do problems 5.3, (1)-(6), draw using construction lines
and straight edge on graph paper