Viewer/onlooker becoming participant.
With paintings more clearly than with sculpture, the viewer is either an onlooker, invited to look at the scene, or a participant, invited to enter the scene, become immersed in it and become part of it.
I am currently really enjoying creating a setting in 2D format - a colour-scape - with oil paints and pigments that does the latter.
In sculpture, installation turns the viewer into a participant more readily than presentation of a finite form.
What happens if you combine a finite form with a painted colour-scape as a backdrop?