lecture week5

8/13/2019 Lecture Week5

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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.


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.


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.


One-point Perspective: Cube drawing


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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.


One-point Perspective: Where to use?


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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.


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.


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.




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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.




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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


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.


Three-point Perspective:


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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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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


Why?


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Example 1


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Example 2


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Example 2 continued --:


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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.


Hatching :


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Hatching


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Hatching Techniques:


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Hatching a single object

Hatching Adjacent objects

Reverse hatching Staggered Hatching


Hatching


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Hatching thin materials


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Density of lines in proportion with component


Hatching

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