This document discusses perspective projection in engineering graphics. It defines perspective projection as representing 3D objects on a 2D surface to give the correct impression of height, width, depth, and position. The document covers key topics such as linear perspective, atmospheric perspective, vanishing points, horizon lines, and examples of one-point and two-point perspective projections. It also discusses the relevance of perspective projections for mechanical engineering applications including 3D modeling, photogrammetry, and virtual/augmented reality.

1. Technical Arts (TA 101AA)
Engineering Graphics
Prof. Nachiketa Tiwari
Department of Design

2. Perspective Projection

3. • Etymology: from perspect- ‘looked at closely’,
from the verb perspicere, from per- ‘through’
+ specere ‘to look’; i. e. to look through.
• Dictionary: the art of representing 3D objects
on a 2D surface so as to give the right
impression of their height, width, depth, and
position in relation to each other.
Perspective: Etymology & Meaning

4.  Projection is a method used to represent a 3-D
object on a plane surface. Projections make the
study of design of an object or structure easier.
Parallel Projections Perspective Projection
Object
Picture plane
Station point
(eye)
Type of Projections

5. Projections
Parallel
All viewing lines are
mutually parallel.
Perspective
Viewing lines are
convergent.
Classification of Projections

6. Trimetric
Cavalier
Cabinet
Isometric
Dimetric
Parallel Projections
Viewing plane is NORMAL to
projection lines.
Axonometric
Viewing plane is NOT
NORMAL to projection lines.
Oblique
Classification of Projections

7. • Functioning of a camera
• Functioning of human eye
Perspective Projection I 7
https://www.pinterest.com/pin/486177722257309568/
Our Goal - To create projection similar to camera
image based on data from orthographic views
Perspective Projection

8.  In the real world, objects exhibit perspective
foreshortening, i.e. distant objects appear smaller
 Example
Perspective Projection

9. Perspective Projection

10.  In contrast to the parallel projection, in perspective
projection parallel lines converge.
 Non-uniform foreshortening of lines in the object
• shape of the object is not preserved.
 Foreshortening: Optical illusion due to which object and
lengths appear smaller as their distance from the centre
of projection increases.
Perspective Views

11. Are the Two Tracks Coverging?

14.  Perspective views and drawings are approximate
representations of objects similar to the perceptions
of our eye.
 Perspective views allow the sketcher to control the
illusion of depth in an image.
 Linear and atmospheric perspective describe how
objects appear in relation to their distance from the
observer.
The Need for Perspective Views

15.  Linear Perspective
• An object’s apparent size changes with distance.
• Obtained when picture-plane is perpendicular to the
ground.
 Atmospheric or Aerial Perspective
• An object’s perception (details, shape, etc.) gets affected
by the presence of atmosphere or space present
between the object and the viewer.
• Distant objects are lack details relative to nearby objects.
• Distant objects appear “bluer” and “lighter” due to
presence of sky.
Types of Perspective Views

16. Atmospheric Perspective
(Photograph)

17. Atmospheric Perspective
(Paintings)

18. Vanishing Points
(VP)

19. Perspective with a Single VP
• Vanishing Point: Location on the Picture Plane where parallel
lines apparently meet.
Perspective Projection I 19
https://iphonephotographyschool.com/perspective-photography/
Vanishing point

20. Horizon Line (HL)
Vanishing Point (VP)
SKY
GROUND
Perspective Views: Terminology
• The sky and the earth appear to meet in the picture plane
along the Horizon Line (HL).
Perspective Projection I 20

21. Perspective Projection I 21
https://www.ancient-origins.net/ancient-places-asia/ramanathaswamy-temple-and-its-infinite-corridors-009649
Vanishing point
HORIZON LINE
Perspective with a Single VP

22. VP Horizon Line (HL)
Perspective with a Single VP

23. VP
Horizon Line (HL)
Perspective with a Single VP

24. HORIZON LINE
VP
SKY
GROUND
Perspective with a Single VP

25. Perspective with a Single VP

26. Perspective View
Perspective with a Single VP

27. Perspective Projection I 27
https://www.thedivineindia.com/rameshwaram-temple-beatuiful-corridor/image/1554
Vanishing point
Vanishing point
HORIZON LINE
Perspective with Two VPs

28. VP1
VP2
HORIZON LINE
SKY
GROUND
SP
Perspective Projection I 28
Perspective with Two VPs

29. VP1
VP2
HORIZON LINE
SKY
GROUND
Perspective Projection I 29
Perspective with Two VPs

30. • The most realistic of all
pictorial systems.
– Closest to what we actually
see.
• Important characteristics
– Objects become smaller with
distance.
– Parallel lines do not appear
parallel.
– Horizontal parallel lines
converge to a single point in
the distant horizon.
Perspective Projection I 30
Some Comments

31. Perspective Projection I 31
https://www.pinterest.com/pin/363032419937395010/
Oblique
Isometric
One point perspective
Two point
perspective
Developing Perspective Views:
Example

32. 1 VP 2 VPs 3 VPs
Perspectives
VP VP
VP VP
VP
VP
Classification of Perspective Views

33. Relevance
 Mechanical and Civil Engineering
– Understanding orthographic views.
– Representing 3D objects in 2D formats.
– Ability to convert legacy drawings into 3D views.
– 3D conceptualization.

34. Relevance
 Experimental mechanics (AE, CE, ME, …)
– Generating 3D pictures and videos from pictures
taken by two synchronized cameras
– 3D Digital Image Correlation
– Photgrammetry
– Stereo-photography and 3D pictures

35. 3D Digital Image Correlation

36. Photogrammetry

37. Stereo-Photography

38. Animations, Gaming, VR,
3D Simulations, etc.

39. 360 Degree Videos and Virtual Tours

40. Thank You!
40