The result of mapping stuff from one geometric model into another, different model.

one example:

As a path traces a space-filling curve, positions along the path can be used as the endpoint of a line segment. Tracing the path twice, once for each end of a moving line segment, can define a function of a region of the plane. If this function is plotted as a colour or an intensity for each point in a region in the plane, an image would result that would (probably) exhibit some characteristics of the original space-filling curve, but from a different dimensional perspective.

I'll put a more detailed (visual) example of this up on my web site as soon as get a RoundTuit.