Pictorial Drawings

GMED UNIT 1GMED 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

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.

Definition:Axonometric projection

PhotoDisk

Types of axonometric projection: Isometric

The three 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

Dimetric Two of the principal faces and axes

are equally inclined to 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.

Lines are drawn to true length.

The object is tipped up or down 3516’.

ISOMETRIC PROJECTION

True measurements are made along three major axes, which are:• VERTICAL

• 30 degrees up to the RIGHT

• 30 degrees up to the LEFT

Drawing object to actual measurement

30° 30°

30°

ISOMETRIC PROJECTION

The basic procedure used in drawing isometrics is to use an isometric grid.Next, draw all lines along the three major axes.

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

In CAD: Use the ellipse command, specifying degree of exposure.

The four-center method

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

Vanishes to one point

VP

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

Worm’s-eye view

Bird’s-eye view

Interior

15-8 Solid Modeling

Types of solid modeling

Image generation

Data extraction

Jonnie Miles

Types of solid modeling:

Wire-frame models

Solid models

Surface models

Types of solid models Constructive Solid Geometry (CSG) (15-8-7

to come) Combines shapes using Boolean operations (union, subtraction, and intersection)

Boundary Representation (BREP) Joins surfaces using extrusion or by

revolution

Quick Quiz

What kind of perspective drawing has two vanishing points?

Angular perspective