GMED UNIT 1
Pictorial Drawings
15-1
Pictorial Drawings
Types of pictorial drawings
Types of axonometric drawings
Isometric drawings
PhotoDisk
Types of pictorial drawings:
 Axonometric projection
Types of pictorial drawings:
 Oblique projection
Types of pictorial drawings:
 Perspective
Definition:
Axonometric projection
A projected view in which the lines of
sight are perpendicular to the plane of
projection, but in which the three faces of a
rectangular object are all inclined to the
plane of projection.
PhotoDisk
Types of axonometric
projection:
 Isometric

The three principal faces and axes
are equally inclined to the plane of
projection
Dimetric

Two of the principal faces and axes
are equally inclined to the plane of
projection
Trimetric

All three faces and axes make
different angles with the plane of
projection
SHAPE DESCRIPTION
The AXONOMETRIC projection is a three
dimensional representation in which the
lines of sight are perpendicular to the plane
of projection.
ISOMETRIC
DIMETRIC
TRIMETRIC
Isometric drawings
 The object is revolved 45
to the horizontal.
 The object is tipped up or
down 3516’.
 Lines are drawn
to true length.
ISOMETRIC PROJECTION
True measurements are made along three
major axes, which are:
• VERTICAL
• 30 degrees up to the LEFT
• 30 degrees up to the RIGHT
Drawing object to
actual measurement
30°
ISOMETRIC PROJECTION
The
basic
procedure
used inthe
drawing
isometrics
Next,
draw
all lines along
three major
axes. is
to use an isometric grid.
ISOMETRIC PROJECTION
When sketching, use isometric grid paper as a
guide.
15-2
Curved Surfaces
in Isometric
Circles and arcs in
isometric drawings
Irregular curves
PhotoDisk
A circle drawn in isometric
 has the shape of an ellipse on any of
the three faces.
Quick Quiz
 Isometric, dimetric, and trimetric are
types of what kind of pictorial drawing?

Axonometric projection
15-3
Common
Features in
Isometric
Isometric sectioning
Drawing conventions:
Fillets, rounds, and
threads
PhotoDisk
Sections in isometric
 The section is taken on an isometric
plane.
 In full section, construction lines
represent the part cut away.
15-4 Oblique Projection
Types of oblique projection
Drawing objects in oblique
projection
Inclined surfaces
Oblique projection drawings
 The object is placed with one face parallel to
the frontal plane.
 The other two faces are placed on oblique
(receding) planes at a convenient angle.
 The three axes are vertical, horizontal, and
receding.
Types of oblique projection
 Cavalier oblique

All lines a drawn in their true length.
 Cabinet oblique

Lines on the receding axis are shortened
by one-half.
15-5 Common
Features in Oblique
Circles and arcs
Sections in oblique
Drawing conventions
Lawrence Lawry
Circles in oblique projection
 When possible, the face having circles
or arcs should be selected for the front
face.
Methods for drawing circles
or arcs on an oblique face:
 The offset
measurement
method
 The four-center
method
 In CAD:
Use the
ellipse command,
specifying degree
of exposure.
Quick Quiz
 What are the two types of oblique
projection?

Cavalier and cabinet
15-6 Parallel, or
One-Point, Perspective
Perspective projection
Types of perspective
drawings
Perspective drawing
and sketching
PhotoDisk
Definitions:
 Picture plane: The plane of
projection
 Station point: The position of the
observer’s eye
Definitions:
 Horizon: An imaginary horizontal line
taken at eye level
 Vanishing point: A point on the horizon
where receding lines converge
Types of perspective
drawings
 Parallel

One vanishing point
Types of perspective
drawings
 Angular

Two vanishing points
Types of perspective
drawings
 Oblique

Three vanishing points
SHAPE DESCRIPTION
There are three types of PERSPECTIVE
projections: 1. PARALLEL
VP
Vanishes to
one point
SHAPE DESCRIPTION
There are three types of PERSPECTIVE
projections: 2. ANGULAR
Vanishes to
one point
Vanishes to
one point
SHAPE DESCRIPTION
There are three types of PERSPECTIVE
projections: 3. OBLIQUE
Vanishes to
one point
Vanishes to
one point
Vanishes to
one point
15-7 Angular, or Two-Point,
Perspective
Angular perspective
drawing and
sketching
Angular perspective
in CAD
Grids for angular perspective
sketching
 Exterior
 Interior
 Bird’s-eye
view
 Worm’s-eye
view
15-8 Solid Modeling
Types of solid modeling
Image generation
Data extraction
Jonnie Miles
Types of solid modeling:
 Wire-frame models
 Surface models
 Solid models
Types of solid models
 Constructive Solid Geometry (CSG) (15-8-7
Combines shapes using Boolean
operations (union, subtraction, and
intersection)
 Boundary Representation (BREP)
to come)

Joins surfaces using extrusion or by
revolution
Quick Quiz
 What kind of perspective drawing has
two vanishing points?

Angular perspective