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Graphical Communication: Lecture 3
SUTS 1
HEF1000 / HES1300 / DEE1243
Graphical Communications
Lecture 3School of Engineering & Science
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TOPICS
Isometric Drawing Oblique Parallel Drawing
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ISOMETRIC DRAWING
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Pictorial Drawing
A three dimensional pictorial is a drawing that shows an objects
three principal planes, much as they would be captured by a
camera
Sometimes they are called Technical Illustrations
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Types
ObliquesCavalierCabinet
AxonometricsIsometricsDimetricTrimetric
Perspectives
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Types of Axonometrics
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Graphical Communication: Lecture 3
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Foreshortening of Cube Edges
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Concept of Isometric Axes
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Isometrics
Axes equally separated (120)
H, W, and D measurements are true size along iso. axes
Angles must be located by coordinates
Circles appear as ellipses on all surfaces
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Isometric Scale
Is used for correct isometric projection.
Allows for the foreshortening of isometric lines.
Is a true representation of the object.
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Isometric Projection vs. Drawing
Isometric projections are foreshortened because the object is
tiIsometric projections are foreshortened because the object is
tipped pped with respect to the viewing plane. Isometric drawings
are not uswith respect to the viewing plane. Isometric drawings are
not usually ually foreshortened because they still appear
proportionate when showiforeshortened because they still appear
proportionate when showing ng the dimensions full size along
isometric axis lines. It is easiethe dimensions full size along
isometric axis lines. It is easier just to r just to sketch or draw
the full dimensionsketch or draw the full dimension.
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Angle for Drawing Isometrics
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Graphical Communication: Lecture 3
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Selection of Isometric Axes
Select the view that reveals as much detail as possible.
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Selection of Isometric Axes
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Isometrics Drawing using the Boxing-In Method
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Making an isometric drawing
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Making an isometric drawing
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Inclined Surfaces in Isometric
Inclined surfaces can not be measured along inclined Inclined
surfaces can not be measured along inclined lines in an isometric
sketch. To locate inclined lines in an isometric sketch. To locate
inclined surfaces you must make measurements along the surfaces you
must make measurements along the isometric axis lines.isometric
axis lines.
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Graphical Communication: Lecture 3
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Arcs in Isometric SketchesArcs are usually sketched by locating
their centers and Arcs are usually sketched by locating their
centers and then boxing in the enclosing parallelogram. Sketch the
then boxing in the enclosing parallelogram. Sketch the arc tangent
to the enclosing box, which is drawn along arc tangent to the
enclosing box, which is drawn along isometric lines.isometric
lines.
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Hidden Lines Hidden lines are not Hidden lines are not
usually shown unless usually shown unless they are needed to
show they are needed to show an unclear feature.an unclear
feature.
The orientation should be The orientation should be chosen so
that hidden chosen so that hidden lines arenlines arent needed.t
needed.
Holes are assumed to go Holes are assumed to go completely
through the completely through the object unless their depth object
unless their depth is indicated with a note or is indicated with a
note or with hidden lines.with hidden lines.
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Isometric Circles & Angles
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Isometric circlesordinate method
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Isometric Ellipses
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The Isometric Ellipse Template
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Graphical Communication: Lecture 3
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Using the Ellipse Template
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Drawing Rounded Corners
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Isometric Ellipse
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Lightly block in the cylinder
Construction of Cylinders
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Construction of Cylinders
Lightly block in the cylinder
Sketch the upper and lower ellipses
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Construction of Cylinders
Lightly block in the cylinder
Sketch the upper and lower ellipses
Connect the ellipses with Tangent lines
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Graphical Communication: Lecture 3
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Construction of Cylinders
Lightly block in the cylinder
Sketch the upper and lower ellipses
Connect the ellipses with Tangent lines
Darken the lines
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Oblique Parallel Drawing
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Which is the cube ?
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Were you right?
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Oblique Drawings
Treated the most descriptive or natural view as the front view,
and is placed parallel to the plane of projection.
Favored by the furniture manufacturing and cabinetmaking
industry.
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Oblique Parallel Projection
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Graphical Communication: Lecture 3
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Oblique Drawing Angles
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Types of Oblique Drawings
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Depth Lines
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Cavalier Oblique
Front view true size Receding Axis Angle
(Normally 30, 45 or 60) is Variable
Depth dimension (receding axis) true size
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Cabinet Oblique
Front view true size Receding Axis Angle
(Normally 30, 45 or 60) is Variable
Depth dimension (receding axis) half size
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Side by Side Comparison
Cavalier Oblique Cabinet Oblique
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Graphical Communication: Lecture 3
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Unnatural Appearance of Oblique Drawing
Oblique drawings of objects having a lot of depth Oblique
drawings of objects having a lot of depth can appear very unnatural
due to the lack of can appear very unnatural due to the lack of
foreshortening.foreshortening.
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Oblique Drawing Rules 1
Place the object so that the view with the most detail (arcs,
circles or irregular face) is parallel to the picture plane.
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Oblique Drawing Rules 2
Place the object so that the longest dimension runs horizontally
across the sheet.
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Oblique Drawing Rules 3
Rule 1 has preference as it is easier to draw the irregular face
without distortion.
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Oblique Drawing Rules 4
Aim to show the object so that its shape is most clearly
presented and is conducive to showing its dimensions.
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Angles in Oblique Angles in front view are drawn true size Other
angles must be located using
coordinates Appearance of angles may be distorted
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Graphical Communication: Lecture 3
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Circles on the Oblique Face
Drawn true size in front view
Drawn as ellipses on receding planes
Layout using a Rhombus
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Circles on the Oblique Face
The circles are plotted in a similar manner to isometric
circles, except that measurements along the 45deg axis are taken
from the half size quadrant.
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Cylinders in Oblique
Front and Back surfaces are circular
Sides are drawn as lines tangent to the front and back
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Start Oblique Drawing
Select front view Draw normal features true size on front plane
Select convenient angle for receding axes (45
or 30) Draw oblique box: receding axes at selected angle apply
appropriate foreshortening
Transfer distances from orthogonal axes along receding axes
(scale if required)
Box in other normal features applying offset Join ends to locate
non-normal features
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Steps of creating oblique drawing
4 x 4 x 4 Cube in Oblique Representation
CABINET CAVALIER GENERAL
DEPTH = 2 SQUARES
DEPTH = 4 SQUARES
DEPTH = 2 DIAGONALS
Scale = ?
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Steps of creating oblique drawing
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Graphical Communication: Lecture 3
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Inclined Surfaces in Oblique
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Oblique vs. Isometric
Circular shapes parallel to the view are Circular shapes
parallel to the view are shown true shape in oblique drawing, shown
true shape in oblique drawing, making them easy to sketch.making
them easy to sketch.
Oblique pictorials are not as realistic as Oblique pictorials
are not as realistic as isometric views because the depth can
isometric views because the depth can appear very distorted. appear
very distorted.
Oblique views cannot usually be Oblique views cannot usually be
generated directly from a 3D model generated directly from a 3D
model using CAD. using CAD.
Oblique is primarily a sketching Oblique is primarily a
sketching technique.technique.
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Reading
BOUNDY, A. W. (2002) Engineering Drawing, NSW, Australia,
McGraw-Hill. Chapter 5, pages 197 206.
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End of Lecture!
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