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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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**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

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