UNIT 2

Orthographic Projections And Projections Of Points

1. List out methods of projection.

Ans-

Following four methods of projection are commonly used,

1) Orthographic projection.

2) Isometric projection.

3) Oblique projection.

4) Perspective projection.

2. What are various orthographic views?

Ans – Front view, Top view, and side views

3. What is orthographic projection?

Ans - orthographic projections is defined as any single projection made by dropping perpendiculars to a plane.

4. How to plot a point situated in the first quadrant?

Ans –

The pictorial view [fig. 1 (i)] shows a point A situated above the H.P. And in front of the V.P., i.e. in the first quadrant. a' is its front view and the top view. After rotation of the plane, these projections will be shown in fig. 1 (ii).

The front view a' is above xy and the top view a below it. The line joining a' and a (which also is called a projector), intersects xy at right angles at a point o. It is quite evident from the pictorial view that a'o = Aa, i.e. the distance of the front view from xy = the distance of A from the H.P. Viz. h. Similarly, ao = Aa', i.e. the distance of the top view from xy = the distance of A from the V.P. Viz. d.

Figure 1

5. How to plot a point situated in the second quadrant?

A point B (fig. 2) is above the H.P. And behind the V.P., i.e. in the second quadrant. b' is the front view and b the top view. When the planes are rotated, both the views are seen above xy. Note that b'o = Bb and bo = Bb'.

Figure 2

6. How to plot a point situated in the third quadrant?

A point C (fig. 3) is below the H.P. And behind the Y.P., i.e. in the third quadrant. Its front view c' is below xy and the top view c above xy. Also, c'o = Cc and co = Cc'.

Figure 3

7. How to plot a point situated in the fourth quadrant?

A point f (fig. 4) is below the H.P. And in front of the V.P., i.e. in the fourth quadrant. Both its projections are below xy, and e'o = Ee and eo = Ee'.

Figure 4