Module 2 : Theory of projections

Lecture 14 : Theories of projections

 

Projection Methods

Projection methods are very important techniques in engineering drawing.

Two projection methods used are:

Figure 2 shows a photograph of a series of building and this view represents a perspective projection on to the camera. The observer is assumed to be stationed at finite distance from the object. The height of the buildings appears to be reducing as we move away from the observer.  In perspective projection, all lines of sight start at a single point and is schematically shown in figure 3. . 

Figure 2. Photographic image of a series of buildings.

 

Figure 3.  A schematic representation of a Perspective projection

 

In parallel projection, all lines of sight are parallel and is schematically represented in figure. 4. The observer is assumed to be stationed at infinite distance from the object.

 

Figure 4.  A schematic representation of a Parallel projection