1. Chapter 9: Visualization and Graphics
Section 9.1 – Why Study Visualization and Graphics?
Visualization and Graphical communication skills are important to many engineering disciplines
Some engineering disciplines no longer require drafting classes of any type
The prevalence of computers in the workplace has increased the need for visualization and graphical communication skills

2. Chapter 9: Visualization and Graphics
Section 9.2 – The Theory of Projection 2
A method is necessary to depict 3D objects on 2D media like drawings and computer screens
Orthographic Projection incorporates a series of 2D views of an object, yet still completely defines the object 2

3. Chapter 9: Visualization and Graphics
Section 9.2 – The Theory of Projection 3
Projection Theory involves 4 specific components:
An object
An observer
A projection plane (or picture plane)
Visual rays 3

4. Chapter 9: Visualization and Graphics
Section 9.2 – The Theory of Projection 4
When the visual rays converge, the projection onto a plane represents a perspective drawing
When the visual rays are parallel (i.e., the observer is very distant), the projection onto a plane represents orthographic projection
The prefix ortho- means perpendicular
Orthographic projection represents views of an object that are all oriented so that the visual rays are perpendicular to the object 4

5. Chapter 9: Visualization and Graphics
Section 9.3 – The Glass Box Theory 5
Suspending an object in a Glass Box, and viewing that object through different faces of that box, is the basis for orthographic projection. 5

6. Chapter 9: Visualization and Graphics
Section 9.3 – The Glass Box Theory 6
If an object’s 3 dimensions are labeled as (1) height, (2) width, and (3) depth, every orthographic view will show exactly 2 of those 3 dimensions:
depth
The front view shows Height and Width only
The right side view shows Height and Depth only
The top view shows Width and Depth only
width
depth
height 6

7. Chapter 9: Visualization and Graphics
Section 9.4 – First and Third Angle Projections 7
The method for how to show and align the different 2D orthographic views leads to 2 main types of projections:
First Angle Projection (used in Europe)
Third Angle Projection (used in the U.S.)
Third Angle Projection
Third Angle Projection shown here is used predominantly in the U.S. 7

8. Chapter 9: Visualization and Graphics
Section 9.5 – The Meaning of Lines 8
Lines used in orthographic projection can have various meanings, including:
Representing an edge of planar surface
The intersection of two surfaces
The limiting element of a curved surface
In orthographic projection, there are only 3 different ways to depict any planar surface:
As an edge (i.e., in Edge View, or EV)
As a true-size surface, where the line of sight is perpendicular to that surface (i.e., True Size, or TS)
As a foreshortened surface 8

9. Chapter 9: Visualization and Graphics
Section 9.6 – Hidden Lines 9
Orthographic views show all features of an object, including those hidden in a particular view
Hidden lines are drawn as dashed lines
Hidden lines represent features of an object which are hidden in that particular orthographic view
Hidden lines are drawn with a thinner line weight, in addition to being dashed, to distinguish them from thicker, continuous lines used for Visible lines. 9

10. Chapter 9: Visualization and Graphics
Section 9.6 – Hidden Lines 10
Orthographic views show all features of an object, including those hidden in a particular view
Hidden lines are drawn as dashed lines
Hidden lines represent features of an object which are hidden in that particular orthographic view
Hidden lines are drawn with a thinner line weight, in addition to being dashed, to distinguish them from thicker, continuous lines used for Visible lines. 10

11. Chapter 9: Visualization and Graphics
Section 9.7 – Cylindrical Features and Radii 11
Cylindrical features are considered either:
Positive e.g., Outside surface of cylinder
Negative e.g., Holes with circular cross-sections
Centerlines are viewed differently in different orthographic views of a cylinder:
When viewing the circle true size, the center line looks like a cross hair (+)
When viewing the cylinder longitudinally, the center line looks like a single line with a break in the middle 11

12. Chapter 9: Visualization and Graphics
Section 9.8 – The Alphabet of Lines and Line Precedence 12
Line Precedence
Visible lines have highest precedence
Hidden lines have 2nd highest precedence; if visible and hidden lines coincide, only the visible lines are shown
Center lines have 3rd highest precedence 12

13. Chapter 9: Visualization and Graphics
Section 9.9 – Freehand Sketching 13
Freehand sketching is very important to the engineer
Quick graphical representations are used frequently to communicate with a variety of others
Proportions are important in freehand sketching
Sketching curved lines represents the greatest challenge in freehand sketching 13

14. Chapter 9: Visualization and Graphics
Section 9.10 – Pictorial Sketching 14
Pictorial sketching: creating a view of the object in which all 3 dimensions are shown
3 Types of Pictorial Sketches:
Axonometric (including isometric)
Oblique
Perspective 14

15. Chapter 9: Visualization and Graphics
Section 9.10 – Pictorial Sketching 15
Isometric Sketches: all 3 dimensions are drawn parallel to each other
Oblique Sketches: The width and height dimensions are drawn perpendicular to each other; the depth dimension is drawn receding at some angle. Depth dimensions are parallel.
Perspective Sketches: At least one dimension has lines which converge on a vanishing point. This is the most realistic looking of all pictorial sketches, yet typically the most time consuming. 15

16. Chapter 9: Visualization and Graphics
Section 9.11 – Visualization 16
Three Types of Surfaces are used to create a three-dimensional object:
Principal surfaces
Inclined surfaces
Oblique surfaces 16

17. Chapter 9: Visualization and Graphics
Section 9.12 – Scales and Measuring 17
A Scaled Drawing means that there is a constant ratio between the length of a feature on a drawing, and the true length of what it represents
A Scale can represent both (a) a numeric ratio and (b) the tool used to draw and measure features.
Types of scales include:
Engineer’s Scale
Architect’s Scale
Metric Scale 17

18. Chapter 9: Visualization and Graphics
Section 9.13 – Coordinate Systems and 3D Space 18
Computer-Aided-Drafting, or CAD, has been common prevalent in many areas of engineering
2D CAD drawings rely on knowledge of x-y Cartesian coordinate systems
3D CAD drawings rely on knowledge of x-y-z coordinate systems 18