3-D Shape
It's called a "double helix".
It is the amount of three dimensional space occupied by a 3-d shape.
The change in a proteins' three dimensional shape or conformation is called denaturation.
Proprioception is the medical term meaning three-dimensional perception.
trompe l'oeil
Having three sides.
"3D"
three dimensional
In 2-dimensional geometry, the first shape circumscribesthe second while the second is inscribed in the first.
cube
Perspective, perhaps.