(Post updated at 31/8/19). This is a 3D movie, which I showed recently at a vision science meeting, (ECVP in Leuven, Belgium).  You will only be able to view the movie in 3D if you have learned how to fuse the two images into one without a viewer, by so-called cross-eyed viewing.  If you don’t have the technique and want to learn it, one of the best Youtube guides is this Youtube tutorial.  (But best to give the technique a miss if you have any eye adjustment problems).

Alternatively, if you have a pair of red/cyan movie glasses, view this next version (ideally full-screen – the larger the better):

The movies are based on one of René Magritte’s most haunting paintings, Carte Blanche, or The Blank Cheque, which you can see at:

https://www.nga.gov/collection/art-object-page.66422.html

Magritte  brilliantly baffles our expectations about spatial organisation, just by bringing into the foreground, in front of the horse and rider, one strip of landscape background, and one tree-trunk.  I wanted to see how the effect would work as a fly-by, 3D animation.

That required a change of motif.  For the animated version the central motif must not touch the ground.  So instead of the horse and rider in the original painting, I chose another Magritte theme: a floating pipe.

The 3D versions set up a competition, between two processes usually in perfect agreement:  on the one hand our judgments of depth based on binocular disparity – the slightly different viewpoint of each eye;  and on the other hand depth arrangements indicated by the occlusion (or masking) of more distant objects by nearer ones.

Different observers see the result in different ways.  Most commonly, when the pipe is interrupted because a tree trunk or background appears in front of it, the different parts of the pipe seem to be at different distances from us.  It can even seem to weave in and out of the tree-trunks, and they can bend around it.  It seems that the occlusion (masking) cues are winning out over the disparity cues.