Engineering Drawing Lecture 2

Engineering Drawing EEE-113Lecture 2

Muhammad Azfar YaqubJawad Mirza

Lecture Contents:• Projections & Views

• Projection: the production of a two-dimensional image of a three-

dimensional object

The projection is achieved by the use of imaginary "projectors".

The projected, mental image becomes our vision of the desired, finished picture

• Projection types:– Parallel projection – Perspective projection

• Perspective projection – Perspective projection is a type of projection

where three dimensional objects are not projected along parallel lines, but along lines emerging from a single point.

– This has the effect that distant objects appear smaller than nearer objects.

– Natural

• Perspective projection

• Parallel projection – In parallel projection, the lines of sight from the

object to the projection plane are parallel to each other.

– Unnatural, made for our ease

• Parallel projections

• Parallel vs Perspective

• Parallel vs Perspective

• Types of Perspective projections– Linear perspective – Curvilinear perspective, etc

• Types of Perspective projections– Linear perspective

–One point Perspective– Two point Perspective– Three point Perspective

– Curvilinear perspective, etc

• One point Perspective

• One point Perspective

• Two point Perspective

• Two point Perspective

• Three point Perspective

• Three point Perspective

• Types of Parallel projections– Oblique projection – Orthographic projection

• Types of Parallel projections– Oblique projection • Cavalier projection • Cabinet projection

– Orthographic projection

• Oblique projection – One plane of the image is set parallel to the plane of projection. – This creates a true shape image of the chosen plane. – but lengths along z-axis are drawn at angle using a reduction factor

• Types of oblique projection • Cavalier projection

– Full depth, No Z-scaling

• Cabinet projection – Half depth, 0.5 Z-scaling

• General projection – Other depths, other Z-scaling

• Cavalier projection– Cavalier means a horseman– the way the things seen from high point– Full depth, No Z-scaling.– Gives correct perception of depth

• Cabinet projection– Famous in furniture industry– Was used in early video games– Half depth, 0.5 Z-scaling– Easily drawn on paper

• Types of Parallel projections– Oblique projection – Orthographic projection

• Types of Parallel projections– Oblique projection

– Orthographic projection • Multiview Projections• Axonometric projection

• Orthographic projection (type of Parallel projection )

– The word comes from the Greek ὀρθός (orthos), meaning “straight”– It is a form of parallel projection, where the view direction is orthogonal to the

projection plane– Orthographic Projection gives us a very clear method of communicating ideas

and objects. It is a method that every engineer in the world recognizes. Because of this we can reproduce any object drawn Orthographically.

• Multiview Projections (type of Orthographic projection )

– Multi-view simply means “multiple views” – So we use several 2D views(pictures) of the object instead of a single

view– As it is a type of Orthographic projection so this we need to make

these views at 90 degrees – up to six pictures of an object are produced, with each projection

plane parallel to one of the coordinate axes of the object.

• Multiview Projections (type of Orthographic projection )

• Multiview Projections (type of Orthographic projection )

The Maximum 6 views:

• Multiview Projection Schemes

– first-angle projection– third-angle projection

first-angle vs third-angle projection

first-angle vs third-angle projection