Ch05_Outline - CHAPTER 5 Multiviews and Visualization...

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CHAPTER 5 Multiviews and Visualization INTRODUCTION Chapter 5 introduces the theory, techniques, and standards of multiviews, which are a standard method for representing engineering designs. The chapter describes how to create one-, two-, and three-view sketches with traditional tools and CAD. Also described are standard practices for representing edges, curves, holes, tangencies, and fillets and rounds. The foundation of multiviews is orthographic projection, based on parallel lines of sight and mutually perpendicular views. Also introduced in this chapter are visualization techniques that can be used to help create and interpret multiviews. 5.1 PROJECTION THEORY Projection methods are developed along two lines: perspective and parallel . Projection theory comprises the principles used to represent graphically 3-D objects and structures on 2-D media. Drawing more than one face of an object by moving your line of sight relative to the object helps in understanding the 3-D form. A line of sight is an imaginary ray of light between an observer's eye and the object. In perspective projection , all lines of sight start at a single point and the object is positioned at a finite distance and viewed from a single point. In parallel projection , all lines of sight are parallel , the object is positioned at infinity and viewed from multiple points on an imaginary line parallel to the object. The 3-D object is transformed into a 2-D representation or a plane of projection that is an imaginary flat plane upon which the image created by the lines of sight is projected. The paper or computer screen on which the graphic is created is a plane of projection. 5.2 MULTIVIEW PROJECTION PLANES Orthographic projection is a parallel projection technique in which the plane of projection is positioned between the observer and the object, and is perpendicular to the parallel lines of sight. Orthographic projection techniques can be used to produce both pictorial and multiview drawings. Multiview projection is an orthographic projection for which the object is behind the plane of projection, and is oriented so only two of its dimensions are shown. Generally three views of an object are drawn, and the features and dimensions in each view accurately represent those of the object. The front view of an object shows the width and height dimensions. The frontal plane of projection is the plane onto which the front view of a multiview drawing is projected. The top view of an object shows the width and depth dimensions. The top view is projected onto the horizontal plane of projection. The side or profile view of an object shows the height and depth dimensions. The side view is projected onto the profile plane of projection. The right side view is the standard side view normally used.
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The top view is always positioned above and aligned with the front view, and the right side view is always positioned to the right of and also aligned with the front view. 5.3 ADVANTAGES OF MULTIVIEW DRAWINGS
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Ch05_Outline - CHAPTER 5 Multiviews and Visualization...

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