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basic technology (Secondary School)

Imagine you are shopping for a chair to go in your living room. You find the perfect one, but it is way too expensive. Fortunately, you have a cousin that builds furniture. Maybe he can build the chair for you! Describing the chair over the phone was more than a challenge. Your cousin suggests you send him pictures of the chair from multiple angles, along with the measurements.

This experience illustrates the process that a furniture designer must go through in order for the manufacturer to create the chair as intended. Three-dimensional drawings can be used to show the overall concept and design, but they are often not clear or detailed enough. Orthographic drawings can help to overcome those challenges.

An orthographic drawing represents a three-dimensional object using several two-dimensional views of the object. It is also known as an orthographic projection. For example, you can see in this image the front, top and side views of an aircraft.

Two Different Styles

There are two different styles of orthographic projections:

First-Angle Projection

In first-angle projection, each view is shown as if the viewer is looking through the object and projecting the image on the other side. This style is the most common one used in Europe. Here is example of first-angle projection (see video). The red arrows represent the view of the observer with the image being projected on the other side.

Third-Angle Projection

In third-angle projection, each view is created as if the object is projecting an image away from itself onto a plane in front of it. It is the image exactly as the observer sees it on that side. Third-angle projection is the preferred style in the United States.

The results of the two styles are very similar. The main difference is the position of the images. It’s all about the perspective. Just like first-person and third-person describes perspective in literature, first-angle and third-angle describe the perspective of the projection. Not knowing which style was used may result in a product with a similar image but incorrect orientation.

Question

  1. differentiate between 1st angle projection and 3rd angle projection
  2. draw object in orthographic form

 

See also

Perspective Drawing

Oblique Drawing

Drawing Practices

Processing of Ceramics and Glass

Metal Processing

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