Lecture 5 Orthographic Projection 19.ppt

..

1. PROJECTION
Amethodtodescribeshapebytheprocessofcausinganimagetobe
formedbyraysofsighttakeninaparticulardirectionfromanobjecttoapicture
plane.Commonlyusedmethodsare
1) Orthographic Projection: If the rays are perpendicular to the picture plane,
the projection is known as Orthographic Projection.
2) Oblique Projection: If the rays are at an angle to the plane, the projection is
known as Oblique Projection.
3) Perspective Projection: If the rays are taken to a particular station point, the
projection is know as Perspective Projection.
Theory Of Orthographic Projection

2. Orthographic Projection

3. Oblique Projection

4. Perspective Projection

5. Oblique Projection Looking through the Plane
(Plane between Observer and Object)

6. Perspective Projection looking through the plane
(Plane between observer and object)

7. Orthographic Projection:
Orthographic projection is another method of projection such that these are views
of a 3D object taken at right angles to the object, in which the projectors (rays
drawn from various points on the object) are parallel to each other and
perpendicular to the plane on which the views are projected.
Theory Of Orthographic Projection

8. Orthographic Projection looking through the plane
(Plane between observer and object)

9. Theory Of Orthographic Projection
THREE BASIC VIEWS:
We will use the concept of orthographic projection to draw the three basic views
1)Thefront(calledaselevation)
2)Top(calledasplan)
3)Sideviewsofobjects
Isometric drawing is three dimensional drawing of the object.

10. Three Views Of an Object
An object is a three dimensional volume enclosed within a series of
interconnected planes. Consider the object shown in the following figure.

11. Three Views Of an Object
.

12. Three Views Of an Object
.

13. Reference Planes/Principle Planes Of Projection
Twoplanesemployedforthepurposeoforthographicprojectionare
Verticalplane(VP)
Horizontalplane(HP)
They intersect each other at right angle
The line where these two planes intersect is called as reference line (xy)
There are two ways of drawing in orthographic -First Angle and Third
Angle. They differ only in the position of the top, front and side views.

14. Reference Planes/Principle Planes Of Projection

15. Procedure for Orthographic Projection
In order to draw the three views of an object
1)The drawing is divided into four zones, similar to mathematical
coordinate system.
2)Each zone contains one orthographic projection of the object.
3)The fourth zone contains the mitre/miter line, which is a line drawn at 45
degrees from the intersection of the principal plane lines.
Mitre line is placed in front of the top view of the object, in order to get the side
view (either left side or right side) of the object for transferring projectors
from top and front views.

16. .
Procedure for Orthographic Projection

17. 1st angle Projections
Iftheobject(whoseviewsarerequired)issituatedinfrontofVPandabove
HP,i.e.inthefirstquadrant
Thismethodoforthographicprojectioniscalledasthefirstangleprojection.
Theplanesareconsideredtobeopaqueinthiscase.
TheFVcomesatthetopandTVcomesatthebottomafteropeningtheplanes
aboutthereferencelinexy.

18. Orthographic Projection (1
st
angle) observing the
object directly
(Object between Observer and Plane)

19. 3rd angle Projections
Iftheobject(whoseviewsarerequired)issituatedbehindtheVPandbelow
theHP,i.e.inthethirdquadrant,
Thismethodoforthographicprojectioniscalledasthethirdangleprojection.
Theplanesareconsideredtobetransparentinthiscase.TheFVcomesatthe
bottomandTVcomesatthetopofthereferencelinexy.
Thesymbolsusedtodefinewhetheraprojectioniseitherfirstangleorthird
angle,areshownbelow.PleasereadNDBhatt’schapter8forfurtherstudy.

20. Orthographic Projection (3
rd
angle) looking through
the plane
(Plane between observer and object)

21. THIRDANGLEPROJECTIONMETHOD
Planeofprojectionisalwaysbetweentheobjectandobserver.

22. THIRD ANGLE PROJECTION METHOD
Projection of Front View

23. THIRD ANGLE PROJECTION METHOD
Projection of Top View

24. THIRD ANGLE PROJECTION METHOD
Bringing Front View and Top View in One Plane
(Always open 1
st
Angle by rotating the H.P. about the V.P.)

25. THIRD ANGLE PROJECTION METHOD
Bringing Front View and Top View in One Plane
(Always open 1
st
Angle by rotating the H.P. about the V.P.)

26. FIRSTANGLEPROJECTIONMETHOD
Objectisalwaysbetweentheplaneofprojectionandtheobserver.

27. FIRST ANGLE PROJECTION METHOD
Projection of Front View

28. FIRST ANGLE PROJECTION METHOD
Projection of Top View

29. FIRST ANGLE PROJECTION METHOD
Bringing Front View and Top View in One Plane
(Always open 1st Angle by rotating the H.P. about the V.P.)

30. FIRST ANGLE PROJECTION METHOD
Bringing Front View and Top View in One Plane
(Always open 1st Angle by rotating the H.P. about the V.P.)

31. THESIXPRINCIPALVIEWS
Theobjectcanbeentirelysurroundedbyasetofsixtransparentplanes,
eachatrightanglestothefouradjacenttoit.

32. •Theobjectisinatransparentbox.
•IntheFirstAngleProjectionmethod,theobserverstandsinsidethebox,
thuskeepingtheobjectbetweenhimandtheplaneofprojection.
•IntheThirdAngleProjectionmethod,theobserverstandsoutsidethe
box,keepingtheplaneofprojectionalwaysbetweenhimandtheobject.

33. •IntheFirstAngleProjectionmethod,theviewsareprojectedtotheother
sideoftheobject.

34. Placement of Six Views in the First Angle Projection Method
(Observe the object from inside the box)

35. Opening the Transparent Box to bring the six views in one plane (1
st
Angle)

36. Opening the Transparent Box to bring the six views in one plane (1
st
Angle)

37. Opening the Transparent Box to bring the six views in one plane (1
st
Angle)

38. Opening the Transparent Box to bring the six views in one plane (1
st
Angle)

39. Opening the Transparent Box to bring the six views in one plane (1
st
Angle)

40. The six views in one plane (1
st
Angle)

41. The six views in one plane (1
st
Angle)

42. The six views in one plane (1
st
Angle)

43. •IntheThirdAngleProjectionmethod,theviewsareprojectedtothesame
sideoftheobject.

44. Placement of Six Views in the Third Angle Projection Method
(Observe the object from outside the box)

45. Opening the Transparent Box to bring the six views in one plane (3
rd
Angle)

46. Opening the Transparent Box to bring the six views in one plane (3
rd
Angle)

47. Opening the Transparent Box to bring the six views in one plane (3
rd
Angle)

48. Opening the Transparent Box to bring the six views in one plane (3
rd
Angle)

49. Opening the Transparent Box to bring the six views in one plane (3
rd
Angle)

50. Opening the Transparent Box to bring the six views in one plane (3
rd
Angle)

51. The Six Views in One Plane (3
rd
Angle)

52. The Six Views in One Plane (3
rd
Angle)

53. The Six Views in One Plane (3
rd
Angle)

54. USING ORTHOGRAPHIC PROJECTIONS
OBJECTORIENTATION
Anobjectcanbedrawninseveralpossiblepositions.Ingeneralthesimplest
positionshallbeused.Theobjectshallbepositionedinsuchawaysothatthe
principalfacesshalllieperpendiculartothedirectionofvision.
SELECTIONOFVIEWS
Itisimportanttochoosethecombinationofviewsthatwilldescribetheshape
oftheobjectinthebestandmosteconomicalway.Oftenonlytwoviewsare
necessary.However,insomecasethreeormoreviewsmightberequiredto
fullydescribetheobject.Unnecessaryviewsshallbeavoided.
VIEWSPACING
Viewspacingisnecessarysothatthedrawingwillbebalancedwithinthe
spaceprovided.

55. Sheet no. 4 3
rd
Angle Projection
(Note: All dimension are in inches)

56. Sheet no. 4 3
rd
Angle Projection
(Note: All dimension are in inches)

57. F.V

58. Orthographic projection
(1
st
angle projection)

109. Ø3
3
4
"
Ø5"
7"
1
2
"
1
3
4
"
1"
5"
8"
3"
R1
1
4
"
R1
1
4
"
R1
1
4
"
1 1/4 Drill 2 Holes

110. Orthographic projection
Use Enlarging scale 2:1
(3
rd
angle projection)
60

114. Orthographic Projection Explained
•https://www.youtube.com/watch?v=KjtAAV
Kie84&list=PLzoPH-
ntAF8fxJ29_jOuXDSVoC_wyjUJ1
Link for orthographic projection of different
objects
•https://www.youtube.com/watch?v=mnQE
z_K9Xx0