Displacement map
A greyscale image used to warp artwork so it follows the wrinkles, weave or curvature of the surface beneath it — what makes a mockup read as real rather than pasted on.
Also called: displacement, depth map
A displacement map drives Photoshop’s Displace filter (or a smart-object displacement step): lighter areas push the artwork one way and darker areas the other, so a logo placed on a crumpled t-shirt or textured paper bends along the folds. Without it, artwork sits flat on the surface and the illusion collapses.
Good mockups ship a tuned displacement map matched to the photo; weak ones omit it, or apply it too strongly and leave artwork that smears. Surface realism is one of the criteria in TheLayer’s methodology.