engineering drawing lecture 2
TRANSCRIPT
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