10 years ago we put a totally gratuitous (but fun!) 3D view of the layers stack into Photoshop Touch. You couldn’t actually edit in that mode, but people loved seeing their 2D layers with 3D parallax.
More recently apps are endeavoring to turn 2D photos into 3D canvases via depth analysis (see recent Adobe research), object segmentation, etc. That is, of course, an extension of what we had in mind when adding 3D to Photoshop back in 2007 (!)—but depth capture & extrapolation weren’t widely available, and it proved too difficult to shoehorn everything into the PS editing model.
Now Mental Canvas promises to enable some truly deep expressivity:
I do wonder how many people could put it to good use. (Drawing well is hard; drawing well in 3D…?) I Want To Believe… It’ll be cool to see where this goes.