Lecture 2: 2-D Transformation and Projection Multi-view Drawing

1 / 32

# Lecture 2: 2-D Transformation and Projection Multi-view Drawing - PowerPoint PPT Presentation

Lecture 2: 2-D Transformation and Projection Multi-view Drawing. Outline. Projection Theory Multi-view Projection Principle views &amp; View placement Projection angle Detail drawing: 1view, 2 view, 3 view drawing Creating multi-view drawing View Selection. Projection Theory.

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.

## PowerPoint Slideshow about 'Lecture 2: 2-D Transformation and Projection Multi-view Drawing' - sharon-dennis

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

### Lecture 2:2-D Transformation and ProjectionMulti-view Drawing

PTT 105/3 Engineering Graphicss

Outline
• Projection Theory
• Multi-view Projection
• Principle views & View placement
• Projection angle
• Detail drawing: 1view, 2 view, 3 view drawing
• Creating multi-view drawing
• View Selection

PTT 105/3 Engineering Graphicss

Projection Theory
• Engineering and technical graphics are depend on projection methods.
• Two methods commonly used:
• Parallel: object positioned at infinity& viewed from multiple points on an imaginary line, parallel to the object.
• Perspective: object positioned atfinite distance & viewed from a single point.

PTT 105/3 Engineering Graphicss

Projection theory comprises of principles used to graphically represent 3D objects on 2D media based on 2 variables:

• Line of Sight (LOS): an imaginary ray of light between an observer’s eye and an object.
• Parallel- all LOS are parallel
• Perspective- all LOS start at a point.
• Plane of projection: an imaginary flat plane where the image created by LOS is projected.

PTT 105/3 Engineering Graphicss

Orthographic Projection
• A parallel projection technique
• The projection plane is placed between observer and object.
• The projection plane is also perpendicular to the parallel line of sight.

PTT 105/3 Engineering Graphicss

Multi-view projection
• Multi-view projection is an orthographic projection for which the object is behind the plane of projection.

PTT 105/3 Engineering Graphicss

Multi-view drawings

i. Employ multi-view projection technique

ii. Generally 3 views of an object are drawn

iii. Each view is a 2D flat image

PTT 105/3 Engineering Graphicss

Example: Multi-view Projection

PTT 105/3 Engineering Graphicss

Multi-view Lines

PTT 105/3 Engineering Graphicss

Multi-view: Planes

PTT 105/3 Engineering Graphicss

Multi-view: Planes

PTT 105/3 Engineering Graphicss

Multi-view: 6 Principle Views
• The 6 principle views are the sixmutually perpendicular views that are produced by six perpendicular planes of projection.
• Image an object is suspended in a glass box, the 6 sides become projection plane showing the six views.

PTT 105/3 Engineering Graphicss

The views are laid flat by “unfolding the glass box”

• This forms the basis of two important multi-view drawing standard:
• Alignment of views
• Fold lines
• Top and bottom views are all aligned vertically & share the same height with dim.
• Rear, left, front and right side are aligned horizontally & share same height with dim.

PTT 105/3 Engineering Graphicss

Fold lines are imaginary hinged edges of the glass box

i. The fold line between the top & front views is labeled H/F

ii. The distance from a point in front view to the H/F is the same as the distance from the corresponding point in the top view to the H/F fold line.

PTT 105/3 Engineering Graphicss

View Placement

PTT 105/3 Engineering Graphicss

View Placement

The arrangement of views may vary as shown, where the top view is considered the central view.

PTT 105/3 Engineering Graphicss

Angle Projection
• There are two standard arrangement of all six views of an object

i. First-angle projection

ii. Third-angle projection

• Each uses different symbol
• The names are derived from the method used to view the object being drawn

PTT 105/3 Engineering Graphicss

In 1st angle projection, the object is placed

in the first quadrant.

• In 3rd angle projection, the object is placed in third quadrant.

PTT 105/3 Engineering Graphicss

Rules:

• Symbols

(a) 1st angle projection (b) 3rd angle projection

PTT 105/3 Engineering Graphicss

Example: 1st and 3rd angle view projection

PTT 105/3 Engineering Graphicss

1, 2 and 3 view drawing

PTT 105/3 Engineering Graphicss

Step in creating multi-view drawing

PTT 105/3 Engineering Graphicss

Creating 3-view drawing
• Draw border/frame, title block, etc.
• Draw border, title block
• Locating the view

i. should be approx. in

centre

ii. distance between view

= total length available

– view length / 3

• Drawing projection lines

PTT 105/3 Engineering Graphicss

Creating 3-view drawing

2. Light construction of the

views

• Draw light/thin horizontal & vertical lines accordingly for front view
• Draw center lines and hidden lines as final
• Draw top (or side) view
• Project top view (or side) from front view using thin, light construction line
• Draw side (or top) view
• Project side view (or top) from front view and top (or side) view
• All arcs and circles should be lined (final) at this stage

PTT 105/3 Engineering Graphicss

Creating 3-view drawing

PTT 105/3 Engineering Graphicss

Creating 3-view drawing

3. Lining in of the views

• To darken all visible edges (lines that represent a hard edge)
• Done using thick, black pencil (0.5mm, 2B)
• Should be done systematically for 3 views
• Start with horizontal line at the top of the top/plan view, working down the page using T-square
• From left hand side, working across the page, line in all vertical lines, using T-square and set square
• Projection lines may be left on the drawing if they are light

PTT 105/3 Engineering Graphicss

Creating 3-view drawing

4. Write dimensioning, notes, annotation, etc.

• Be aware of redundant dimensioning

5. Complete drawing by writing the rest of title block, parts list & revision table, and others

PTT 105/3 Engineering Graphicss

View Selection

4 basic decisions:

1. Determine the best position. The objectmust bepositioned such a way that the surface of major features are either perpendicular or parallel to glass planes

PTT 105/3 Engineering Graphicss

View Selection

2. Define the front view. Should show the

object in natural state and show most features

PTT 105/3 Engineering Graphicss

View Selection
• Determine the minimum number of views needed to completely describe the object.

PTT 105/3 Engineering Graphicss

View Selection

4. Determine other views that fewest number of hidden lines

PTT 105/3 Engineering Graphicss

THANK YOU…

PTT 105/3 Engineering Graphicss