ORTHOGRAPHIC DRAWINGS.

Orthographic drawings usually consist of a front view, a side view and a plan, but more views may be shown for complex objects with lots of detail. A drawing board and parallel motion or T-square is used to project one view from another. Orthographic drawing may be done using first angle projection or third angle projection. An orthographic projection of the shape on the right is shown below.                                               
                 ISOMETRIC DRAWINGS.

Isometric drawings are 3D drawings. They show three sides, all in dimensional proportion, but none are shown as a true shape with 90 degree corners. All the vertical lines are drawn vertically but all horizontal lines are drawn at 30 degrees to the base line. Isometric is an easy method of drawing 3D images.                                                                   

OBLIQUE DRAWINGS.

Oblique drawings are also used in engineering. The object is drawn with the most distinguishing features facing directly towards the observer, showing the true shape of these features. Circular features like round holes can be drawn on this front face as true circles. In other 3D forms, circular features must be drawn as ellipses.To show the 3D effect, parallel lines (called 'lines of sight') are drawn from the front face at an angle.