IOT

POLY ENGINEERING2-24

March 5, 2010

1. Quiz Monday on the following:1. Describe the differences between isometric,

perspective, and oblique drawings2. On diagonal grid paper, draw an isometric

based on given orthographic projections3. Find the starting point for orthographic

projections and isometric drafting

IOT

POLY ENGINEERING2-10

• A way of showing depth, like isometric• Part orthographic / part isometric:

– One face is true form– Parallel lines behind; either:

» Full scale» Half scale» Three-quarter scale

Review OBLIQUETY

PE 3

: PIC

TORI

AL

IOT

POLY ENGINEERING2-10

• Latin: perspicere – to see through• An approximate representation of an image as it is

perceived by the eye. • The most characteristic feature of perspectives is that

objects are drawn:

Smaller as their distance from the observer increases

Review PERSPECTIVETY

PE 3

: PIC

TORI

AL

IOT

POLY ENGINEERING2-10

Review ISOMETRICTY

PE 3

: PIC

TORI

AL

Isometric Cube:

1) all lines equal length;

2) all faces equal area;

3) perimeter is a hexagon

• From Greek: Equal Measure– Isos: Equal– Metron: Measure

• The scale along each axis of the projection is the same• True form parallel lines are shown as parallel (note colors

below)• All isometrics: simple construction

IOT

POLY ENGINEERING2-24

QUIZ REVIEW

1. Isometrics:1. Parallel projection2. True size (you can measure the lengths accurately)

2. Perspectives:1. Shown as it is perceived by the eye2. Object gets smaller the farther away it is

3. Obliques:1. One face is orthographic projection2. The rest of object is parallel projection

2. On diagonal grid paper, draw an isometric based on given orthographic projections

QUIZ REVIEW

Quiz drawing will be an altered version of one of your homeworks:

1. Add width of front view to width of right view.

2. Add the space we will put between: 1.5”

4.5” + 2” = 6.5”

HORIZONTAL STARTING POINT

6.5” + 1.5” = 8”

3. Subtract from the total width.10” – 8” = 2”

4. Divide by 2.Horizontal Starting Point = 1”

1. Add height of front view to height of top view.

2. Add the space we will put between: 1.5”

3” + 2” = 5”

VERTICAL STARTING POINT

5” + 1.5” = 6.5”

3. Subtract from the total height.7.25” – 6.5” = .75” = 3/4”

4. Divide by 2.Vertical Starting Point = .375” = 3/8”

IOT

POLY ENGINEERING2-21

1. Describe an isometric view1. Height2. Width 3. Depth

(of the front view)

Tech

nica

l Gra

phic

Com

mun

icati

onDRAFTING ISOMETRIC DRAWINGS

2. Prepare drawing paper3. Locate center of drawing space

Tech

nica

l Gra

phic

Com

mun

icati

onDRAFTING ISOMETRIC DRAWINGS

45 degree triangle

Construction Lines

4. Plot starting point of drawing

Tech

nica

l Gra

phic

Com

mun

icati

on

DRAFTING ISOMETRIC DRAWINGS

30-60-90 triangle

1) ½ W2) ½ D3) ½ H

Starting Point

IOT

POLY ENGINEERING2-21

5. Complete isometric drawing

Tech

nica

l Gra

phic

Com

mun

icati

on

DRAFTING ISOMETRIC DRAWINGS

Starting Point

SOLUTIONS

IOT

POLY ENGINEERING2-21

Draft the following isometrics on drawing paper (use dimensions previously given for left drawing):

3 March 10

2”

2”

4”

1”1”

1”

CLASSWORK – Drafting Isometrics

IOT

POLY ENGINEERING2-24

Introduction to AutoCAD

AutoCAD is a communication technology tool:

Creating neat, accurate drawings and designs.

There are numerous features – we will concentrate on the most important ones.

One of the most important actions within the AutoCAD program is the drawing of straight lines.

Before we learn the LINE command, let’s take a look at how we normally draw lines by hand.

Tech

nica

l Gra

phic

Com

mun

icati

on

Auto

CAD

Absolute Coordinates

0 1 2 3 4 5 6 7 8 9 10

0 1

2 3

4 5

6 7

8 9

10

Plot lines:

FROM: TO:1,1 1,5

1,5 4,9

4,9 7,5

7,5 7,1

1,5 7,5

3,1 3,4

3,4 5,4

5,4 5,1

0,1 10,1

IOT

POLY ENGINEERING2-3

Absolute coordinates are based on the origin (0,0), expressed as an ordered pair x,y. All other points are also expressed in the form x,y and the values of x and y are based on the distance from the origin.

If we desire to draw a line, we must give the location of both endpoints, expressed as an ordered pair x,y where the origin is used as a reference point.

Absolute Coordinates

Auto

CAD

Relative Coordinates

0 1 2 3 4 5 6 7 8 9 10

0 1

2 3

4 5

6 7

8 9

10

Plot lines:

FROM: 0,1

@ 10,0

FROM: 1,1

@0,4

FROM: 0,5

@10,0

FROM: 0,5

@5,2

@5,-2

FROM: 9,5

@0,-4

Auto

CAD

Relative Coordinates

0 1 2 3 4 5 6 7 8 9 10

0 1

2 3

4 5

6 7

8 9

10 Plot lines:

FROM: 3,1

@0,2

@1,0

@0,-2

FROM: 5,1

@0,3

@3,0

@0,-3

Offset distance = .5What is the distance between the two orange lines?

IOT

POLY ENGINEERING2-24

Communication TechnologyIntroduction to AutoCAD

Relative coordinates are not based on the origin (0,0). Instead, we use the @ symbol followed by an ordered pair x,y. This means “starting where we are AT, go over (or back) x and up (or down) y.

If we desire to draw a line using relative coordinates, we must give the location of the first endpoint (usually using Absolute coordinates), followed by @x,y for the second endpoint.

IOT

POLY ENGINEERING2-24

Auto

CAD

Relative CoordinatesIn AutoCAD, you do not have to specify the start point with coordinates – you can just click anywhere.

IOT

POLY ENGINEERING2-24

Absolute and Relative Coordinates

FROM: 0,5

@5,2

@5,-2

FROM: TO:

1,1 1,5

1. On the graph paper provided, draw coordinate axes about half the size of your graph paper.

2. Draw an object with at least 10 lines.

The end points must land on intersections of graph paper lines.

3. Tear a blank sheet of notebook paper in half.

4. On one half, write out the absolute coordinates required to draw the object.

5. On the other half, write out the relative coordinates required to draw the object.

Someone else will be drawing your object based on the coordinates you create.

Homework

1. Trade absolute coordinates with someone in class. Put his/her name on a blank area of your graph paper, write the word “absolute,” and draw the object based on the coordinates.

2. Trade relative coordinates with someone in class. Put his/her name on a blank area of your graph paper, write the word “absolute,” and draw the object based on the coordinates.

3. Bring back your partner’s coordinate sheets tomorrow. IOT

POLY ENGINEERING2-24