Foreshortening is the rate at which an object gets smaller relative to its distance from the viewer.
Using a box as an example, if the back seems like it's receding into space a lot more then it's dramatic foreshortening and usually means that the object is either SUPER large or super close to you.
Usually things that are normal sized that you interact with have shallow foreshortening which means that these far ends are still receding into space, but feels like it's at a less extreme rate.
The lines of the box converge towards vanishing points.
Usually if it's super dramatic, you'll see the vanishing points and you can kind of measure them as converging at a certain point. This makes the object seem kind of HUGE or close up.
Most of the time objects will just have a slight bit of foreshortening (shallow foreshortening) so the edges are converging, but the vanishing point is really far away, which makes it difficult to align everything correctly!
One common error is for these edges of the box to not be aligning correctly to the foreshortening. As you can see below in the drawabox.com example, this person is drawing the lines off the box to see if they are converging. If it's off, that means the box is not even. The lines should generally be angling towards a similar vanishing point as they go away from the viewer.
by Drawabox
Below, if we test the vanishing points of the ends of the table we are able to see that the table should be corrected in the red areas.
By Karen Poblete
This is only a testing mechanism that will allow someone to kind of see where your intuition is off. When I draw, I have this knowledge, but I definitely don’t have mathematical accuracy— I mostly have drawn enough boxes and shapes in space to get it right about like 80% of the time, which is convincing enough.
HOWEVER that isn’t an excuse to not to know that these vanishing points exist. For example in the student example below, there needs to be some foreshortening for the center plate. I didn't need to map out a real vanishing point, but knowing that the object should be smaller makes for a more convincing foreshortened object.
By Jake Kiley
