I have seen this in an installation by an artist called Jennifer steinkamp. It appears as though the “background2 of the piece is transparent, as all there is visible is an animated strip that is placed across a wall. I am pretty sure that it is done with with a projector, although this is a more high end one than I own. I want the projection to blend into the space so that just my animation of fluid paint is visible. I have thought that I could simulate this by using a background of grey, as it is unlikely that the space will be completely dark, ideally it would be. Hope this is clearer?!