1. ENGINEERING GRAPHICS 1E7
Lecture 4: Orthographic Projections 2

2. Projections (1)
Projections transform points from n (here, n = 3) dimensional space into a space of dimension less than n (here, n = 2)
Points to be considered,
Location of object
Location of observer
Plane of projection
Projectors

3. Projections (2)

4. Parallel Projections

5. Perspective Projections

6. Oblique Projections
Projectors are parallel to each other but not perpendicular to projection plane
 An oblique projection shows front and top surfaces that include the three dimensions of height,  width,  and  depth.  
The  front  or  principal  surface  of an  object  (the surface toward the plane of projection) is parallel to the plane of projection.
Effective in pictorially representing objects

7. Orthographic Projections
Orthographic  projections  are   drawings  where  the  projectors, the observer or station point remain parallel to each other and perpendicular to the plane of projection.
Orthographic  projections  are   further  subdivided  into  axonometric projections and multi-view projections.
Effective in technical representation of objects

8. Axonometric
The observer is at infinity & the projectors are parallel to each other and perpendicular to the plane of projection. #
A key feature of axonometric projections is that the object is inclined toward the plane of projection showing all three surfaces in one view.   
The length of the lines, sizes of the angles, and proportions of the object varies according to the amount of angle between the object and the plane of projection. 

9. First Angle Projection
Front view is Elevation

10. How to draw plan and elevation?
First Angle Projection
How to draw plan and elevation?
For drawing plan and elevation 3D visualisation of objects are essential

11. How to draw end view? First Angle Projection 2
Green arrows and purple arrows show equal distance

12. First Angle Projection 3
Points to remember:
The ‘front view’ (or elevation) is the view with maximum information.
The ‘plan’ is below the ‘elevation’ (in projection).
The ‘end view’ is placed on the right if viewed from left side of object and on the left if viewed from right side.
‘End view’ and plan face inwards from ‘elevation’.
Green arrows and purple arrows show equal distance

13. Third Angle Projection
Front view is Elevation

14. How to draw plan and elevation?
Third Angle Projection
How to draw plan and elevation?
For drawing plan and elevation 3D visualisation of objects are essential
In 3rd angle projection planes are transparent and objects are viewed through them

15. How to draw end view? Third Angle Projection 2
Green arrows and purple arrows show equal distance

16. Third Angle Projection 3
Points to remember:
The ‘front view’ (or elevation) is the view with maximum information.
The ‘plan’ is above the ‘elevation’ (in projection).
The ‘end view’ is placed on the right if viewed from right side of object and on the left if viewed from left side.
‘End view’ and plan face outwards from ‘elevation’.
Green arrows and purple arrows show equal distance

17. Example 1

18. Example 2

19. Example1 movie

20. Example 2 movie