Foreshortening is to represent (or show with drawing lines) the long axis of an object by contracting (drawing them shorter) so as to create an illusion of projection or extending out into space.
The degree that the object is extended out into space from your plane of vision, determines how contracted you draw it.
We know that the object is literally the same distance across, but the farther it is extended out, the narrower it is viewed. When we view an object contracted, then it is to be drawn narrower.
In other words, how much an object is angled away from your plane of vision, determines how much you flatten (or contract) it when drawing.
TIP: Disregard what you know about the subject and draw only the parts that are actually seen from your plane of vision (or perspective).
Understanding an ellipse is essential to drawing three dimensional . . .
See a more detailed tutorial on my how to draw an ellipse, complete with photos and drawings.
An ellipse is a flattened circle that you will come across in drawing a vase, cup or glass. It appears narrower (its height is diminished) the nearer it is to your eye level (or to your plane of vision). It is a foreshortened circle.
Understanding where the ellipse is located in your plane of vision will tell you how closed or open it is to be drawn (or how contracted).
When you are viewing an ellipse on a table straight-on (at eye level) with no angle, then you will see only a straight edge.
However if you stand up you will be viewing it at an angle, and an ellipse will appear again. The higher you stand, the larger it will become (the less contracted it will become).
People say to "draw what you see". However when your brain tries to translate what you see onto paper, drawing can become tricky.
It takes putting your subject matter into perspective (usually by foreshortening) and then drawing it accurately.
Drawing three dimensional objects on one dimensional paper so as to create the illusion of a three dimensional object, is one of the reasons why drawing is so good for your brain health.
Drawing engages both the right hand side (creative side) of the brain and at the same time engages the left hand side (logical/mathematical side).
Drawing is as good (perhaps better) for your brain health as math -- it uses the same logical thinking and at the same time, it engages the illogical, creative side.
Translating what you see on paper is challenging. Do at least one drawing a day for great brain health!
Creating art and crafts builds new neural pathways in your brain and is a great way to keep your noggin healthy. Keep creating for optimal brain health!
Check out my draw a leaf with two twists tutorial -- it'll be good for your brain health!