PERSPECTIVE VIEW OF ENGINEERING DRAWING WITH EXAMPLE

Prespective View

1. WAWERU HANNAH
NYAKIO
B02/53847/2012

2. PERSPECTIVE DRAWING
Perspective drawing is a drawing technique used to illustrate
dimension through a flat surface. It is an approximate
representation of a three-dimensional object on a flat surface as it
is seen by the eye.
The two most characteristic features of perspective are that
objects are drawn:
I. Smaller as their distance from the observer increases
II. Foreshortened: the size of an object's dimensions along the
line of sight are relatively shorter than dimensions across the line
of sight.
There are many forms used under perspective drawing such as,
one perspective, two-point perspective, three-point perspective,
four-point perspective, five-point perspective, bird’s eye view,
worm’s eye view and others.

3. FORESHORTENING
Foreshortening is the visual effect or optical illusion that causes an
object or distance to appear shorter than it actually is because it is
angled toward the viewer.
Additionally, an object is often not scaled evenly: a circle often
appears as an ellipse and a square can appear as a trapezoid.
Although foreshortening is an important element in art where
visual perspective is being depicted, foreshortening occurs in
other types of two-dimensional representations of three-
dimensional scenes.
Some other types where foreshortening can occur include:
I.Oblique parallel projection drawings. Two different projections of
a stack of two cubes, illustrating oblique parallel projection
foreshortening ("A") and perspective foreshortening ("B")
II.Epimetheus (lower left) and Janus (right). The two moons appear
close because of foreshortening; in reality, Janus is about 40,000
km farther from the observer than Epimetheus.
(i)
(ii)

4. ONE POINT
A linear perspective in which all
parallel lines meet at a single point
on the horizon.
Therefore one establishes the flat
side of the object, then makes all
the receding lines to meet at a
single vanishing point.

5. TWO POINT
A graphical technique in which a
three-dimensional object is
represented in two- dimensions and
in which parallel lines in two of its
dimensions are shown to converge
towards two vanishing points.

6. THREE-POINT
Linear perspective in which
parallel lines along the width of
an object meet at two separate
points on the horizon and vertical
lines on the object meet at a point
on the perpendicular bisector of
the horizon line.

7. FOUR POINT
Four-point perspective, also called infinite-point perspective, is the
curvilinear variant of two-point perspective.
As the result when made into an infinite point version), a four point
perspective image becomes a panorama that can go to a 360 degree
view and beyond – when going beyond the 360 degree view the artist
might depict an "impossible" room as the artist might depict
something new when it's supposed to show part of what already
exists within those 360 degrees.
This elongated frame can be used both horizontally and vertically and
when used vertically can be described as an image that depicts both a
worm's- and bird's-eye view of a scene at the same time.
Like all other foreshortened variants of perspective (respectively one-
to six-point perspective), it starts off with a horizon line, followed by
four equally spaced vanishing points to delineate four vertical lines.
The vanishing points made to create the curvilinear orthogonals are
thus made ad hoc on the four vertical lines placed on the opposite
side of the horizon line. The only dimension not foreshortened in this
type of perspective is the rectilinear and parallel lines perpendicular
to the horizon line – similar to the vertical lines used in two-point
perspective.

8. FIVE-POINT
A curvilinear perspective
with its vanishing points are
mapped into a circle such
that four vanishing points
are at the cardinal headings
i.e. n, w, s, e and one at the
circle origin.

9. ZERO POINT
Since vanishing points exist only when parallel lines are present in
the scene, a perspective with no vanishing points ("zero-point"
perspective) occurs if the viewer is observing a non-linear scene.
The most common example of a nonlinear scene is a natural scene
(e.g., a mountain range) which frequently does not contain any
parallel lines.
A perspective without vanishing points can still create a sense of
depth.

10. METHODS OF CONSTRUCTION
Several methods of constructing perspectives exist, including:
Freehand sketching (common in art)
Graphically constructing (once common in architecture)
Using a perspective grid
Computing a perspective transform (common in 3D computer
applications)
Mimicry using tools such as a proportional divider (sometimes
called a (variscaler)

11. LIMITATIONS
i.Only three sides of a component are shown.
ii.No feature is a true proportion. They are not drawn to a
constant scale.
iii.Sectioned perspective drawings are often confusing.
iv.Sometimes a hidden outline is shown which can be confusing.
v.Dimensions are often difficult to show.

It is due to these disadvantages that engineering
drawings are rarely drawn in perspective projection.