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Unit 6Orthographic

Projection

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TOPICS

Object representation

Glass box concept

Line convention

Orthographic projection of point,

line, plane, surfaceand object.

Multiview projection

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OBJECT REPRESENTATION

Axonometric projectionMultiview projection

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MULTIVIEW PROJECTIONThree principle dimensionsof an object

Width Depth

Height

Width

Height

Depth

Dept

h

can be presented onlytwo in each view.

Adjacent view(s)

is needed tofulfill the sizedescription.

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REVOLVE THE OBJECT

Front view Right side view

Top view

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OBSERVER MOVE AROUND

Front view Right side view

Top view

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THE GLASS BOX CONCEPT

Bottom view

Left side view

Rear view

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HeightWidth

D

epth

History

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Orthographic

Projectionof Object Features

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OBJECT FEATURES

Edges are lines that represent the boundary

between two faces.

Corners Represent the intersection of two or

more edges.Edge

Corner

Edge No edge

No corner No corner

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Surfaces are areas that are bounded by edges

or limiting element.

Limiting

element

is a line that represents the last visible

part of the curve surface.Surface Surface Surface

Limit

Limit

OBJECT FEATURES

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PROJECTION OF OBJECT

The views are obtained by projecting all object

features to the picture plane.

You have to project the remaining surfaces which are

invisible too !

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s

s

s

PROJECTION OF OBJECT

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PROJECTION OF OBJECT

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Line Convention

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LINE CONVENTION

Precedence of coincide lines.

Hidden line drawing.

Center line drawing.

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PRECEDENCE OF LINE

VisiblelineOrder ofimportance Hiddenline Centerline

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HIDDEN LINE PRACTICE

Hidden line should join a visible line, exceptitextended from the visible line.

Correct

No !

Join

Leavespace

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Correct No !

Hidden line should join a visible line, exceptitextended from the visible line.

LeavespaceLeavespace

HIDDEN LINE PRACTICE

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Hidden line should intersect to form L and Tcorners.

Correct

No !

L T

HIDDEN LINE PRACTICE

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Hidden arcs should start on a center line.

HIDDEN LINE PRACTICE

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CENTER LINE PRACTICEIn circular view, short dash should cross at the

intersections of center line.

For small hole, center line is presented as thin

continuous line.

Center line should not extend between views.

Leave space Leave space

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Leave the gap when centerline forms a

continuation with a visible or hidden line

LeavespaceLeavespaceLeavespace

Leave

space

Center line should always start and end with

long dash.

CENTER LINE PRACTICE