Engineering Design and Presentation Introduction to Pictorials, Specifically Isometrics Copyright © Texas Education Agency, All rights reserved.

Pictorials break down into two (2) groups  Group #1= Perspective or Central Projection.  Group #2= Parallel Projection that includes Orthographic (Multiview), Oblique, & Axonometric. 2 Copyright © Texas Education Agency, All rights reserved.

Group #1: Perspective Drawings  Perspective drawings produce the view that is most realistic.  A perspective drawing is often referred to being the “camera” or photo view.  There are three main types of perspective drawings depending on how many vanishing points are used.  These are called one-point, two-point, and three-point perspectives. 3 Copyright © Texas Education Agency, All rights reserved.

Group #2: Oblique and Isometric Drawings  Obliques Isometrics 4 Copyright © Texas Education Agency, All rights reserved.

Oblique Pictorials Oblique pictorials don’t look as realistic as perspectives or isometrics because the side or depth view looks distorted or “stretched out”. However, circular shapes in the front view aren’t distorted and that makes them easier to draw. If you do have to draw an oblique, cabinet projection is the method you use because the depth is halved making it look more realistic. 5 Copyright © Texas Education Agency, All rights reserved.

Axonometric Projections  We are going to focus only on Isometric’s, but there are others.  There are three (3) types: Isometric: all angles are equal or Dimetric: only the top & right side view are the same angles. Trimetric: none of the angles are equal. 6 Copyright © Texas Education Agency, All rights reserved.

Why draw Isometrics?  They are BOTH true size, or dimensionally correct, and visually pleasing to the eye.  Think of them as a combination of a perspective and an oblique drawing, using the best from each. 7 Copyright © Texas Education Agency, All rights reserved.

Oblique vs. Isometric. Which one is the most realistic looking? 8 Copyright © Texas Education Agency, All rights reserved.

Draw back of Isometric? Circles in an Isometric  Circles distort shape, or become ellipses, when drawn in an isometric sketch.  To sketch an isometric circle, locate the center and then sketch the box that would enclose the circular shape. Draw the ellipse tangent to the lines of the box. This is very similar to how you’d sketch a circle, just an angle. 9 Copyright © Texas Education Agency, All rights reserved.

Hidden Lines Generally, you will NOT draw hidden lines in any pictorial. You draw the object so that they aren’t necessary to be drawn to show the shape of the object. You assume that holes go all the way through unless it’s noted otherwise. 10 Copyright © Texas Education Agency, All rights reserved.