## ENG 004 Lecture 4, Oct 9, 2012

### Announcements

• Turn in HW #1 now. Place in stack corresponding to your section.
• Four wait listed students have been added.
• Read beginning of Chapter #5
• Lecture HW #2 will be posted after class.

### Topics

Drawing Types

3D to 2D, 2D to 3D

Diagrams

## Drawing Types

Projection theory is in Chapter 5

## Projections and Perspective

• One point perspective
• Two point perspective
• Three point perspective
• Parallel Projection (infinite focal point)

## Two point perspective

• Most realistic
• Does not preserve scale

## Parallel Projections

Parallel projection corresponds to a perspective projection with an infinite focal length (the distance from the image plane to the projection point)

### Orthographic projection

Parallel project representation of a three dimensional object in two dimensions

### Axonometric

To measure along axes.

### Multiview Projections

Up to 6 views of an object are projected onto planes perpendicular to the coordinate axes. The view positions follow one of two schemes: First Angle or Third Angle

### Pictorial Projections

Image of object from skewed direction to reveal all axes

Isometric, Dimetric, Trimetric

## Axonometric Projections

Type of parallel projection, more specifically a type of orthographic projection, used to create a pictorial drawing of an object, where the object is rotated along one or more of its axes relative to the plane of projection

## Isometric Projections

All three axes are equally foreshortened and angled 120 degrees apart.

Lines are parallel.

## Oblique

Projects an image by intersecting parallel rays (projectors) from the three-dimensional source object with the drawing surface (projection plane).

θ is typically 45 degrees

x-y scales are the same

z scale is between 0 and 1, usually 1/2

## Diagrams

Ideas are captured in a visual format using symbols, words, lines, etc.

• shows relationships
• show critical issues or functions
• organize concepts
• visual note taking
• free form

### Types

• Graph based: tree, network, flow chart, Venn
• Chart based: histogram, bar char, pie char, function graph, scatter plot
• Infographics

## Flow chart

Represents an algorithm or process

## Venn diagrams

Show all possible logical relations between a finite collection of sets

Click me

## Engineering Diagrams

• Free body diagrams
• Block diagrams
• Circuit diagrams
• Exploded views
• Hydraulic diagrams
• Sankey diagrams

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