Refractive Glass: Noise Bends the Backdrop
Frosted glass blurs what is behind it; real glass moves it. The difference is one SVG filter: feTurbulence paints a cloud, feDisplacementMap reads red as how far each backdrop pixel travels along x and green as y, and it runs before the blur averages anything. The lens and the frost are siblings, never nested: an element with a backdrop-filter starts its own backdrop root, so a lens inside the frosted box would find nothing left to bend. The filter travels as a data URI: a fragment reference resolves against the document, and this demo runs in a sandboxed frame with an opaque origin, where Chrome refuses it and paints the frame empty. Chrome is also the only engine that bends a real backdrop. Safari and Firefox run an SVG filter on an element but never on a backdrop, so what bends here is a copy of the scene's own gradient, pinned with background-attachment: fixed so it lands on the original to the pixel. That only works because this demo painted what is behind the glass. Over arbitrary content, a page scrolling under a header, those two get the frost and nothing else.