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Projections of points.pptx
- 1. 08-Jul-09 SBT 1 ORTHOGRAPHIC PROJECTION Principle of projections * If the rays of light made to fall on the wall across the object, shadow / image of that object will appear on that wall. That means, object is being projected on the wall. * If straight lines are drawn from various points on the contour of an object to meet a plane, the object is said to be projected on that plane. * The image we are getting on that plane is called projection (view) of the object. * The lines from the object to the plane are called projectors. Methods of projection 1. Orthographic projection 2. Isometric projection 3. Oblique projection 4. Perspective projection
- 2. 08-Jul-09 SBT 2 Definition of Orthographic projection When the projectors are parallel to each other and also perpendicular to the plane, the projection is called orthographic projection. Three types of views …….. 1. Front View (FV) 2. Top View (TV) 3. Side View (SV) Reference plane 1. Vertical plane (VP) 2. Horizontal plane (HP) 3. Profile plane (PP) Reference line (x-y line)
- 3. A a’ Horizontal Plane (HP) Vertical Plane (VP) I Quad II III IV 50 50 TV Turn HP to coincide with VP x y 3 SBT 08-Jul-09 Concept of Projections a FV
- 4. x y 50 40 a a' Projection of Point (In 1st angle projection method) 4 SBT 08-Jul-09 VP HP Projector Locus
- 5. VP HP I II III IV A B C D a’ a d d’ b’ b c c’ Projections of Points (In all quadrant) a’ a b b’ c c’ d d’ 5 SBT 08-Jul-09 I II III IV x y
- 6. Points to keep in mind ……… Projection of a point on a Vertical Plane (VP) is called Front view (FV) Projection of a point on a Horizontal Plane (VP) is called Top View (FV) Distance of a point with respect to HP is specified by the FV Distance of a point with respect to VP is specified by the TV 6 SBT 08-Jul-09 Front view of point ‘A’ is represented by ‘a’’ Top view of point ‘A’ is represented by ‘a’ I angle – FV is obtained above the x-y line and TV below x-y line II angle – FV and TV both are obtained above x-y line III angle – FV is obtained below the x-y line and TV above x-y line IV angle – FV and TV both are obtained below x-y line
- 7. 08-Jul-09 SBT 7 No. Position of point (10 mm from given RP) Specified by Representation 1 FV a’ = 10 2 FV a’ = 10 3 TV a = 10 4 TV a = 10 Handy way to remember
- 8. 08-Jul-09 SBT 8 No. Position of points with respect to RP Representation 1. 2. 3. 4. 5. 6. 30 mm below HP and 20 mm in front of VP a’ = 30 a = 20 40 mm above HP and 20 mm behind VP a’ = 40 a = 20 30 mm above HP and 40 mm in front of VP a’ = 30 a = 40 15 mm below HP and 25 mm behind VP a’ = 15 a = 25 Lies on HP and 20 mm behind VP a’ = 0 a = 20 Lies on VP and 10 mm below HP a’ = 10 a = 0 It’s time to check yourself…….