2. 1. DIHEDRAL
SYSTEM
In order to include all the necessary details for any
technological object’s manufacture, when drawing a
sketch or a plane of such an object, it is usually necessary
to represent it from different positions. The views of an
object are defined as the different images that are
obtained when looking at the object from above, from
below, in front, behind and the sides of the object. To
draw the views of an object, the dihedral system uses
the projections of an object on the perpendicular
planes that intersect forming a dihedral (orthogonal). In
this way, each point of the object is represented in
both planes.
3. DIHEDRAL SYSTEM: REPRESENTATION
OF VIEWS
To define an object in detail, we will normally use three
views: FRONT (elevation), OVERHEAD (plan) and SIDE
(profile).
Front: projection on the vertical plane (object seen
from the front).
Overhead: projection on the horizontal plane (object
seen from above)
Side: projection on the profile plane (object seen from
one of the sides).
6. 2. PERSPECTIVS
The perspective is the representation of a three-
dimensional object or figure in a plane of two
dimensions, that is, to give volume on the paper to a
figure or object of three dimensions.
There are several systems for drawing objects in
perspective:
Isometric perspective.
One-point perspective.
7. To represent figures in three dimensions you need 3 axes: X, Y, Z
(where Y is the width, Z is the height, X is the depth).
In isometric perspective the X, Y, Z (perpendicular in reality) axes
are drawn forming angles of 120° with each other in the plane of
the paper.
2.a)
ISOMETRIC
PERSPECTIVE
8. HOW TO DRAW
IN ISOMETRIC
PERSPECTIVE
To draw in isometric are
usually used templates
like the one shown:
To draw a figure or piece
in three dimensions you
can use several methods
9. Draw a prism
that contains
the piece.
Remove from
the elevation
the part of the
prism that is
empty.
Do the same
from the plant
and the profile.
HOW TO DRAW
IN ISOMETRIC:
Sustractive
method
10. Draw plan of the piece using the overhead view.
Complete in height what you see from the front and the
appropriate side.
See the video from the link.
HOW TO DRAW
IN ISOMETRIC:
Additive
method
11. 2.b) Ortogonal
perspective
We have to draw the axles
according to the dimensions of
the paper sheet adding the third
one (Depth) in an oblique
direction. To do this we draw the
diagonal of the squares the we
have in the paper sheet.
We also have to do a
transformation to this dimension,
giving to it half on the length that
the normal dimensions have.
Remember that in maths
normal, orthogonal and
perpendicular are synonymous.
14. 3.1. SCALES
They show the proportion between the real size of the
object and the drawing.
There are three types of scales:
• Full Scale (escala natural): when the drawing is the
same size as the real object. It is expressed as 1:1 (one
to one)
• Scale to reduce (escala de reducción): when the
drawing is smaller than the real object.
Scale 1:10 : The drawing is a tenth of the size of the real
object.
• Scale to enlarge (escala de ampliación): when the
drawing is bigger than the real object.
Scale 10:1 : The drawing is ten times as big as the real
object.
