To be three dimensional, a piece of art must have color
depth
a flat surface
a human actor I WILL MARK BRAINLIST

It has to have depth

Explanation:

Depth, or a 3rd axis

1 is vertical

2 is horizontal

3 is depth

The three-axis are used to make stuff three dimensional.

based on the images pictured above, the major difference between the two cathedrals: the cathedral of notre dame and the amiens cathedral, is that the cathedral of notre dame emphasizes the horizontal lines while the amiens cathedral emphasizes the vertical lines.