Multiview Projections 1
Glass Box Theory
Some Characteristics
Parallel projectors
Projectors normal to
projection plane
Object positioned
with one side
parallel to
projection plane
Only one side visible
to describe object
need more than one view
Glass Box Theory - 1
Mutually perpendicular
projection planes (sides of
glass box)
Position object inside glass
box. PEB orthogonal to sides
of glass box
Six principal views
(front/back, top/bottom,
left/right)
Frontal (F), Horizontal (H),
Profile (P) projection planes
Object dimensions (width,
height, depth)
Hinges – fold lines (H/F, F/P)
Glass Box Theory - 2
Images projected onto
the projection planes
Glass Box Theory - 3
Sides of glass box
hinged (H/F, F/P) so
that when opened …
Glass Box Theory - 4
the views are aligned
as shown here:
Glass Box Theory - 5
For many objects, three
views are sufficient
View Alignment/View Placement
Arrangement of Views
Top and Front are
vertically aligned,
share width
dimension
Front and Right are
horizontally in line,
share height
dimension
Top and right are
not aligned, share
depth dimension
Transfer of Depth
Every point or
feature in one
view must be
aligned on a
parallel projector
in an adjacent /
related view
Line Conventions
Alphabet of lines
Visible lines – used to represent visible
edges on an part
Center Lines – used to identify centers
of circles and axes of cylinders (holes).
Also used to identify symmetry and to
show path of motion
Multiview Drawing of a Cylinder
Centerlines only
cross in circular
view
Extend center
lines about 5mm
past object edge
NOTE: Limiting elements refer to the extents of a
curved surface. In engineering graphics lines are
use to represent limiting elements, just as they
are used to represent edges.
Center Lines
Center lines used to indicate axis of a hole feature
In circular view,
crossing center lines
used
Hole and arc edge
concentric; center
lines extend beyond
arc
In rectangular
views, single center
line represents axis
of hole
Hidden Lines
Hidden lines are used to show hidden features
(e.g., edges, limiting elements, etc.) on an object
Holes – locate
limiting elements
Surfaces – locate
edge view of a
surface
Change of planes
– locate position
of a change of
plane or a corner
Multiview Projections 1
This is the end!