Civ102_wk8_Chp3.pdf - CIV 102 COMPUTER AIDED ENGINEERING DRAWING Chapter 3 Orthographic Drawing 2 Orthographic Drawing Projection Theory \u2022 The solid

# Civ102_wk8_Chp3.pdf - CIV 102 COMPUTER AIDED ENGINEERING...

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CIV 102COMPUTER AIDED ENGINEERING DRAWINGChapter 3Orthographic Drawing
2Orthographic DrawingProjection TheoryThe solid objects in the space are 3D. Although we perceive them in 3D (due to shading, color, etc.), we see them in 2D (You can not see the back of a wall) !We can only see surfaces (2D shapes) that reflect light.Thus we project 3D solids to 2D shapes.
3Engineering and technical graphics are also dependent on projection methods. The two projection methods primarily used are perspective and parallel. Both methods are based on projection theory.Orthographic DrawingProjection Theory
EY/MHA fall084Two variables involved in all projection methods; line of sight (the direction we look)plane of projection (the plane where the 2D shapes are seen). Orthographic DrawingProjection TheoryPerspective projection(the lines of sight intersect at the same point)Parallel projection(the lines of sight are parallel)
5Perspective projection mimics the human eyeOrthographic DrawingProjection TheoryObject at a distance (e.g. The Sun)Object seen smaller than the original
EY/MHA fall086Figure shows a perspective drawing of a road, as well as the ortographicside view of the same road. In the perspective view, the sky meets the ground at a line called the horizonor eye level. The plane upon which the object is projected is called the picture plane, where lines of sight from the object from an outline of the object.Orthographic DrawingProjection Theory
7Orthographic projection: 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.

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• Fall '18
• jane
• Accounting, Orthographic Projection, Multiview Drawings, Orthographic Drawing