Chapter 9: Visualization and Graphics Section 9.1 – Why Study Visualization and Graphics?

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

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

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

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.

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

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.

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

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.

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.

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

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

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

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

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.

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

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

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