A TRE (at three)

Height,width, 'depth'
A painting,
A space ...

A cube has six fields,
regular squares.

To make it more clear that the one in the distance comes very near in being the one at the front, I gave them the same size.

The canvas is a regular square,
I suppose that leaves five fields.
One on the left, one on the right,
One above, one under,
One in the distance

Four edges.

Heigt, width, 'depth'
A painting,
A space ...