From cbmvax!uunet!CUVMA.BITNET!LOJBAN Fri Mar 13 07:30:38 1992 Return-Path: Received: by snark.thyrsus.com (/\==/\ Smail3.1.21.1 #21.19) id ; Fri, 13 Mar 92 07:30 EST Received: by cbmvax.cbm.commodore.com (5.57/UUCP-Project/Commodore 2/8/91) id AA08210; Fri, 13 Mar 92 06:36:38 EST Received: from pucc.Princeton.EDU by relay1.UU.NET with SMTP (5.61/UUNET-internet-primary) id AA08368; Fri, 13 Mar 92 03:47:20 -0500 Message-Id: <9203130847.AA08368@relay1.UU.NET> Received: from PUCC.PRINCETON.EDU by pucc.Princeton.EDU (IBM VM SMTP V2R2) with BSMTP id 0667; Fri, 13 Mar 92 03:46:48 EST Received: by PUCC (Mailer R2.08 PTF011) id 8151; Fri, 13 Mar 92 03:46:35 EST Date: Fri, 13 Mar 1992 08:41:32 GMT Reply-To: Ivan A Derzhanski Sender: Lojban list From: Ivan A Derzhanski Subject: Necker Cube To: John Cowan , Eric Raymond , Eric Tiedemann In-Reply-To: "Mark E. Shoulson"'s message of Thu, 12 Mar 1992 22:46:28 -0500 <13416.9203130346@cogsci.ed.ac.uk> Status: RO > Date: Thu, 12 Mar 1992 22:46:28 -0500 > From: "Mark E. Shoulson" > > A Necker Cube is that picture of a cube in 2D, y'know, wherein you can't > tell which way it is because you don't know how the lines cross? Lessee > how good my ASCII is: > > +-----------------+ > |\ |\ > | \ | \ > | +--------------+--+ > | | | | > | | | | > | | | | > | | | | > +--+--------------+ | > \ | \ | > \| \| > +-----------------+ > > Well, you get the picture. Those two spots where the two squares intersect > are ambiguous, in that you don't know which line is in front, and that > means you don't know which square is in front. If you draw it so you can > tell, but with the disambiguation in an impossible fashion, you get the > famous irrational cube (q.v. various Escher prints. _Belvedere_ is a good > example, as the guy in the dungeon is holding an irrational cube and > there's a picture of a Necker Cube on the floor with the key intersections > circled). Haud a wee. If I remember correctly, the cube in _Belvedere_ is not an ambiguous one, because you can tell which line is which, only they go in a way that makes it impossible for the cube to exist in real life, like so: +=================+ |\\ |\\ ||\\ ||\\ || +=================+ || || || || || || || || || || || || || || || || +=================+ || \\|| \\|| \|| \|| +=================+ Ivan