lecture week5
TRANSCRIPT
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All objects we look at have perspective. Objects closer to us are bigger than objects
further away. In other words as objects get further away they seem to 'vanish into the
distance. A perspective pictorial most closely resembles the view seen by the eye or
camera and is the most realistic form of pictorial.
There are three main perspective systems which allow you to construct an object
using a ruler.
One point perspective
Two point perspective
Three point perspective
Engineering Design Pictorial drawing
Perspective
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Using one perspective, parallel lines converge to one point somewhere in the
distance. This point is called the vanishing point (VP). This gives objects an
impression of depth.
When drawing using one point perspective all objects vanish to one common point
somewhere on the horizon.
Engineering Design Pictorial drawing
One-point Perspective:
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1. Draw one side of the cube and select a vanishing point
(marked with an 'X').
2. Draw very faint lines from each corner to thevanishing point.
Engineering Design Pictorial drawing
One-point Perspective: Cube drawing
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3. Draw horizontal and vertical lines for the 'back of
the cube.
4. Go over the faint perspective of the cube so that
the lines that make up the cube are dark and
sharp.
Engineering Design Pictorial drawing
One-point Perspective: Cube drawing
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Engineering Design Pictorial drawing
One-point Perspective: Try completing the drawings of L-shapes andT-shapes in single point perspective:
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One point perspective though is of only limited use, the main problem being that the
perspective is too pronounced for small products making them looking bigger than they
actually are.
Engineering Design Pictorial drawing
One-point Perspective: Where to use?
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Engineering Design Pictorial drawing
One-point Perspective: Where to use?
So when would you use one point perspective?
One area where one point perspective can be quite useful is for sketching room layouts.
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Two Point Perspective is a much more useful drawing system than the more simple One
Point Perspective. Objects drawn in two point perspective have a more natural look.
In two point perspective the sides of the object vanish to one of two vanishing points on
the horizon. Vertical lines in the object have no perspective applied to them.
Engineering Design Pictorial drawing
Two-point Perspective:
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STAGE ONE: Mark two vanishing points on the paper and faintly draw a line
between them - this is called the horizon line. Then draw one side/edge of the cube
beneath the horizon line and in the centre between the vanishing points.
Engineering Design Pictorial drawing
Two-point Perspective: Cube drawing
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STAGE TWO: Draw faint lines from the ends of the edge of the cube to the vanishing
points
STAGE THREE: Draw two more edges of the cube so that two sides of the cube
can be clearly seen.
Engineering Design Pictorial drawing
Two-point Perspective: Cube drawing
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STAGE FOUR: Draw faint guidelines from the ends of these lines to either vanishing
point.
STAGE FIVE: Use a fine black pen to draw over the outline of the cube.
Engineering Design Pictorial drawing
Two-point Perspective: Cube drawing
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By altering the proximity of the vanishing points to the object, you can make the object
look big or small.
Vanishing Points close to the object Vanishing Points far away from product
Engineering Design Pictorial drawing
Two-point Perspective: example
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Three point perspective is a development of two point
perspective. Like two point it has two vanishing points
somewhere on the horizon. But three point perspective
also has a vanishing point somewhere above or below
the horizon which the vertical vanish to.
The nearer the vanishing point is to the object, the
bigger the object looks.
Look at these buildings. All the vanishing points are too
close. This has caused an excessive amount of verticalperspective. Learning how to apply vertical perspective
is the key to making your drawings realistic.
Engineering Design Pictorial drawing
Three-point Perspective:
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Engineering Design Pictorial drawing
Three-point Perspective: Example
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Engineering Design Sectioning
Correctly drawn orthographic views that show all hidden lines may not
clearly describe an objects internal details and can be shown in a cross-sectional view, called a Section
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Engineering Design Sectioning
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Engineering Design Sectioning
Introduction
Sections and sectional views are used to show hidden detail more
clearly
Created by using a cutting plane to cut the object
A section is a view of no thickness and shows the outline of the object at
the cutting plane
A sectional view, displays the outline of the cutting plane and all visible
outlines which can be seen beyond the cutting plane
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Sectional views are produced to:
clarify detailsshow internal features clearly
reduce number of hidden detail lines
aid dimensioningshow cross-section shape
clarify an assembly
Engineering Design Sectioning
Why?
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Engineering Design Sectioning
Example 1
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Engineering Design Sectioning
Example 2
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Engineering Design Sectioning
Example 2 continued --:
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Engineering Design Sectioning
Example 2 continued --:
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To distinguish the solid portions from the hollow areas of an object
To indicate the type of material that was used to make the object
General Purpose "Section Lining", which is also used to represent "CastIron", uses medium, thick, lines drawn at a 45 angle and spaced 1/16 to
1/8" apart
Different materials have different patterns of lines and spacings
Section lining should be reversed or mirrored on adjoining parts when
doing an Assembly Section.
Engineering Design Sectioning
Hatching :
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Engineering Design Sectioning
Hatching
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Engineering Design Sectioning
Hatching Techniques:
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Hatching a single object
Hatching Adjacent objects
Reverse hatching Staggered Hatching
Engineering Design Sectioning
Hatching
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Hatching thin materials
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Density of lines in proportion with component
Engineering Design Sectioning
Hatching