Question

Difference between isometric drawing and isometric projection

Answer 1

Isometric Drawings are the quickest and easiest of all pictorials to draw and are therefore the most commonly used. In an isometric drawing the three normal surfaces of a rectangular solid will have equal angles between them (120 degrees). However there is a distinct difference between isometric drawings and isometric projections. This is particularly important because most computer generated pictorials are actually projections.

The biggest visual difference between isometric drawings and isometric projections is the size of the two images. The isometric drawing is drawn using 100% true length measurements on the height, width, and depth axes. However, in isometric projections the height, width and depth are displayed at 82% of their true length.

In isometric projections the object is first rotated about the Y axis by -45 degrees. Then the object is rotated about the X axis by 35 degrees. Because the normal surfaces of the object are no longer parallel or perpendicular to the picture plane, the image edges will appear foreshortened on each axis by 18%. The foreshortened view is called an isometric projection.

When you draw a pictorial on a computer, the image that appears on the screen is a projection, and therefore it is foreshortened. The big advantage of drawing these pictorials on the screen is that the object may be easily rotated about the axes in a countless number of positions once the data for the object's features have been entered.

Answer 2

The isometric drawing is drawn using 100% true length measurements on the height, width, and depth axes. However, in isometric projections the height, width and depth are displayed at 82% of their true length. In isometric projections the object is first rotated about the Y axis by -45 degrees.