ENGINEERING GRAPHICS 1E7 Lecture 4: Orthographic Projections 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

Projections (2)

Parallel Projections

Perspective Projections

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

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

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. 

First Angle Projection Front view is Elevation

How to draw plan and elevation? First Angle Projection 1 How to draw plan and elevation? For drawing plan and elevation 3D visualisation of objects are essential

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

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

Third Angle Projection Front view is Elevation

How to draw plan and elevation? Third Angle Projection 1 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

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

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

Example 1

Example 2

Example1 movie

Example 2 movie