This is an example of framing. the pillars and and alter frame around the cross on the wall.
The is an example of bad merging. It looks as though the cross is coming out of the subject’s head. With our eyes, we can see in 3D, but an image is 2D, which gives the illusion of the cross coming out of their head.
This a good example of merging. Both subject’s are separate and not overlapping each other.