This document provides an overview of different types of projections used in computer graphics, including perspective projection, parallel projection, orthographic projection and axonometric projection. Perspective projection uses projecting lines that converge at a vanishing point to give a realistic 3D view, while parallel projection preserves object sizes and shapes. Types of parallel projection include orthographic, oblique, multi-view and axonometric, and types of perspective projection include one point, two point and three point perspectives. The document compares key characteristics of perspective and parallel projections.

2. Projection Models
Computer Graphics
Presented by: Iram Toqeer

3. Presentation Overview
 Projection
 Some Examples of Projection
 Concept of 2d in Mathematical Definition
 Concept of 3d in Mathematical Definition
 Difference between 2d v s 3d
 Advantage v s Disadvantage of 2d
 Advantage v s Disadvantage of 3d
 Types of Projections
 Perspective Projection
 Vanishing Point
 Types of Perspective Projection

4. Presentation Overview
 Types of Oblique Parallel Projection
 Cavalier, Cabinet Oblique PP
 Types of Axonometric Orthographic PP
 Isometric, Di-metric, Trimetric Axonometric PP
 Characteristics Of Perspective Projection
 Characteristics Of Parallel Projection
 One, Two, Three Point Perspective Projection
 Parallel Projection
 Types of Parallel Projection
 Orthographic Parallel Projection
 Oblique Parallel Projection
 Types of Orthographic Parallel Projection
 Multi-view Orthographic PP
 Axonometric Orthographic PP

5. Projection in graphics
 Projection: Project object to the view plane.
 It is the process of converting a 3D object into a 2D object.
 View plane: It is an area of world coordinate system which is projected into viewing
plane.
 Projectors: It is also called a projection vector. These are rays start from the object
scene and are used to create an image of the object on viewing or view plane.

6. Some Examples of Projection
Projection line
View-plane
Object

7. Concept of 2d in Mathematical Definition
 In mathematics and physics, a 2D figure is plotted on two axes, namely the
x- and y-axes.

8. Concept of 3d in Mathematical Definition
 In mathematics and physics, 3D figure is plotted on three axes,
namely the x-, y-, and z-axes.

9. Difference between 2d & 3d
Description 2D 3D
Definition 2 dimensional 3 dimensional
Dimensions height and length height and length, width
Mathematical Def x-and y-axes x-, y-, and z-axes
Examples Circle, rectangle, square Cube, cylinder

10. Advantage vs Disadvantage of 2d
Advantage
 Easy controlling — It is easy to handle without any tutorials.
 Saves time — The production lead time for 2D animation is low and it is quicker to
produce.
 Low production cost — It is cheaper when compared to 3D animation.
 Simple and works without complexity– 2D involves less technology and software
and hence it is easier to produce when compared to 3D.
Disadvantage
 It looks boring — Traditional animation can sometimes seem to be boring.
 Less demand — With the growth of 3D animation most people prefer to watch 3D
animation movies as compared 2D.

11. Advantage vs Disadvantage of 3d
Advantage:
 We can enjoy 3d things more, then the 2d. Object can better understand.
 In demand — Most of the people now prefer 3D rather than 2D.
 Games in 3d are also popular because it has better graphic quality for gamming
environment.
Disadvantage
 Lack of simplicity .
 3D technology is expensive.
 Eye can be feel uncomfortable by the goggles. Some goggles can be spread eye
infections.

12. Types of Projections
Projection
Parallel Perspective

13. Perspective Projection
 Projection lines are drawn from the object towards view plane.
 Projection Reference Point or center of projection: Point at which projection line converge.
 According to that PRP we make a image.
 In perspective, PRP is finite point.
Projection line
View Plane
Object

14. Use of Perspective Projection
All architect, graph man use perspective projection because they make architecture of a big
building or car. To do this, they ready image of building or car into paper or see 3d view of building
or car in computer through perspective projection. If they use parallel projection, the size of image
big so, its image render into paper is difficult.

15. Perspective Projection in Real Life
 Reality can be complex that equally valid observations from differing perspectives
can appear to be contradictory.

16. Vanishing Point
 Parallel line that are not parallel to the viewing plane converge to a vanishing point.
 Based on vanishing point we meet three types of Perspective Projection.

17. Types of Perspective Projection
Perspective
One point Two point Three point

18. One, Two, Three Point Perspective Projection
 One-point Perspective: A one-point perspective means that the object has a single
vanishing point.
 Two-point Perspective: A two-point perspective means that the object has two
vanishing points.
 Three-point Perspective: A three-point perspective means that the object has three
vanishing points.

19. Parallel Projection
 In parallel projection, coordinate positions are transformed to the view plane along parallel
line. In other word, parallel Projection use to display picture in its true shape and size.
View Plane
DOP
Object
View plane

20. Use of Parallel Projection
 Parallel projections are used by architects and engineers because since the
parallelism of an object's lines and faces is preserved, and direct measurements
can be taken from the image. .
Object

21. Types of Parallel Projection

22. Orthographic Parallel Projection
 Line are parallel to each other and make an angel of 90 degree with view plane.

23. Oblique Parallel Projection
 Line are parallel to each other but they are not making an angle of 90 degree with view plane.
 They are inclined with some angel with view plane.

24. Types of Orthographic Parallel Projection

25. Multi-view Orthographic Parallel Projection
 Multi-view Projection is a way of drawing an 3D object from different directions.
Usually a front, side and plan view are drawn so that a person looking at the drawing
can see all the important sides.

26. Use of Multi view
 All architects and graph man make map for example stairs
 To do this, they take image of front, side, top view through multi view.
Top
Side Front

27. Axonometric Orthographic Parallel Projection
 Axonometric projection is a type of orthographic projection used for creating a drawing of an
object, where the lines of sight are perpendicular to the plane of projection, and the object is
rotated around one or more of its axes to reveal multiple sides.

28. Types of Oblique Parallel Projection

29. Cavalier, Cabinet Oblique PP
 Cavalier: The Cavalier projection makes 45° angle with the projection plane. In a cavalier
projection, All projection lines are projected with no change in width, In other words we
can say there is no foreshortening of projection lines.
 Cabinet: The Cabinet projection makes 63.4° angle with the projection plane. , All
projection lines are projected with change in width, In other words we can say there is
foreshortening of projection lines.

30. Types of Axonometric Orthographic PP
Axonometric
Isometric Di-metric Trimetric

31. Isometric, Di-metric, Trimetric Axonometric PP
 Isometric: The three axes like (x, y, z) are equal inclined to the projection line.
 Di-metric: Two axes like (x, y, z) are equal inclined to the projection line.
 Trimetric: All three axes make different angles with the projection line.

33. Characteristics of Perspective Projection
Types of perspective projection include: one-point, two-point and three-point perspective projection.
Perspective projection cannot give the accurate view of object
Perspective projection represents the object in three dimensional way
Perspective projection forms a realistic picture of object
Projector in perspective projection is not parallel.
Perspective projection cannot preserve the relative proportion of an object
The lines of perspective projection are not parallel

34. Characteristics of Parallel Projection
There are two types of parallel projection, that is, orthographic and oblique parallel projection.
Parallel projection can give the accurate view of object.
Parallel projection represents the object in a different way.
Parallel projection does not form realistic view of object.
Projector in parallel projection is parallel.
Parallel projection can preserve the relative proportion of an object.
The lines of parallel projection are parallel.