projection types

7/29/2019 Projection Types

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Types of Projection


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Perspective:When the human eye views ascene, objects in the distance appear smaller

than objects close by - this is knownas perspective. While orthographic projectionignores this effect to allow accuratemeasurements, perspective definition shows

distant objects as smaller to provide additionalrealism.


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GL2:4

Projection plane

3-D object View point

Projectionrays

2-D projection

Engineering graphics are obtained by projection

from the 3-D object to the viewing surface (the

projection plane)

Perspectiveprojection


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GL2:5

Perspective projection is useful for

non technical communications

Perspective renderings for marketing, etc. are readilyobtained with computer-aided drawing (CAD) systems


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Axonometric: prepared by the projectionof objects on the drawing surface so that

they appear inclined with three sides showingand with horizontal and vertical distancesdrawn to scale but diagonal and curved linesdistorted.

(not to be confused with orthographicprojection) used to create a pictorial drawingof an object, where the object is rotated

along one or more of its axes relative to theplane of projection.

GL2:6


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Orthographic: projection of a single

view of an object (as a view of thefront) onto a drawing surface in whichthe lines of projection are perpendicularto the drawing surface and parallel toeach other.

GL2:7


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Oblique: In both oblique projectionand orthographic projection, parallel lines ofthe source object produce parallel lines in theprojected image. The projectors in obliqueprojection intersect the projection plane at anoblique angle to produce the projected

image, as opposed to the perpendicular angleused in orthographic projection.

GL2:8


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GL2:9


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GL2:10

Bertoline,eta

l.Fig.

9.2

Orthogonal (multiview) Axonometric

Oblique Perspective


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GL2:11

Parallel to

projection plane

Normal to

projection plane

Orthogonal

Inclined to

projection plane

Normal to

projection plane

Axonometric

Parallel to

projection plane

Inclined to

projection plane

Oblique

Orthographic projection(Parallel projectors)

Categories of orthographic projection

Principal

plane of

object

Projectors


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GL2:12

GL2 13


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GL2:13

GL2 14


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GL2:14

GL2 15


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GL2:15

Top horizontal plane

Frontverticalplane

Left profile plane

Third-angle orthogonal projection

Top view

Front view

Leftsideview

Glass projection box

First quadrant

Third quadrant

GL2 16


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GL2:16

Third-angle orthogonal projection

vertical plane

horizontal plane

left profile plane

leftsideview

depth

horizontal plane

verticalplane

leftprofile

plane

depth behindvertical plane

height belowhorizontal plane

top(plan)

view

width

height front

view

depth depth behindvertical plane

O th hi P j ti


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Orthographic Projection:

Isometric Sketches from

Orthographic Views

Sometimes you are asked to constructIsometric sketches from Orthographic viewsto develop visualization skills.

The box method is one way to do this.

For some problems, the box method maynot be very helpful.


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Isometric Sketches from Orthographic

Views1. Find the object's overall dimensions from the

orthographic views and sketch that size boxon isometric dot paper.

D

H

W



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Isometric Sketches from Orthographic

Views

2. Sketch the top, front, and right side views intheir appropriate locations on the box.



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Isometric Sketches from

Orthographic Views

3. Add/remove lines until the view is complete.

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