Talk:Penrose triangle

Priority

I find it difficult to believe that this object was first devised by Roger Penrose. I would bet any of the classical Masters must have been aware of it, or at least, Projective Geometers, etc... To the point: the claim that Penrose was the inventor comes from what source? Thanks. Pfortuny 07:20, 13 Apr 2004 (UTC)

Lionel and Roger Penrose published a letter in the British Journal of Psychology regarding the triangle (the article is correct though, as it was Roger Penrose who came up with it). Whether they were the first inventors of it or not is irrelevent - if anyone else came up with it before, either they didn't bother to make others aware of its existence, or that knowledge was lost again. Average Earthman 07:37, 1 Jun 2004 (UTC)

• I've now found the cite - Penrose, Lionel and Roger Penrose, "Impossible objects: A Special Type of Visual Illusion," British Journal of Psychology, vol. 49, 1958, pp. 31-33
• OK, you piqued my interest, so I did a more thorough search on the web - and I've now found someone who came up with the triangle before them - Swedish artist Oscar Reutersvard, who drew 'impossible figures' in Japanese perspective. Apparently, neither Escher nor Penrose were aware of his work. Average Earthman 08:16, 1 Jun 2004 (UTC)
• Reutersvald made a career out of drawing these sorts of things, and published huge numbers of them, and if more modern mathematical researchers didn't know about it, then maybe they should have asked a graphic designer friend or someone who'd done a "history of art" course about it. As for popularisation, "impossible" artworks had been hanging in museums for centuries before Penrose "popularised" the tribar by publishing a piece on it in that influential mass-media cultural touchstone ... the British Journal of Psychology (??). Ahem. ErkDemon 23:24, 20 June 2007 (UTC)

We may be able to give the Penroses credit for identifying these shapes, and for trying to give them an academic classification, and popularising them amongst mathematicans, but these sorts of things had already been hanging in museums for rather a long time. Try Googling for an image of "The Magpie on the Gallows" by Pieter Brueghel or Apolinère Enameled by Marcel Duchamp. These are not exactly unknown artists. ErkDemon 23:24, 20 June 2007 (UTC)

This seems to be taking the discussion further afield. Penrose isn't credited with inventing impossible objects, just the tribar. Those images you mention are obviously related, but are not the tribar itself. Some of the appeal of the tribar seems to be from the simplicity of the triangular shape. Reutersvard should probably also be credited, but it's interesting to note that his "Impossible triangle" does have substantial difference with the tribar as usually depicted nowadays: it is made of a series of cubes rather than three beams. I suspect the reason Penrose's depiction is more often seen is that it is more visually striking. --C S (talk) 09:44, 9 March 2009 (UTC)

Image not showing up

At the bottom of the page the image for the Penrose rectangle is not showing up for me. Anyone know the problem? --Captain538[talk] 01:01, 12 October 2006 (UTC)

Dunno. But Wikipedia is not an instruction manual, so intructions to draw it should probably be ommited. Although, I do like your idea. We could probably put it to good use somewhere, I just don't know where that is. --172.191.129.64 01:01, 13 October 2006 (UTC)

Change main title to "Tribar"?

Ive been seeing these figures in books for years, and I don't think I've ever seen them referred to as Penrose triangles: they've always been referred to as "tribars", or "impossible tribars".

It may be that these things are referred to as "Penrose" objects within the mathematical community, but I really don't think its the popular name for them (although some Penrose fans do seem to be fond of trying to get things named after their guy).

Rather than getting into disputes over "Penrose triangles" vs "Reutersvärd triangles", couldn't we just refer to the things as "tribars" and have done with it? A quick unscientific Google poll for hits for "tribar" vs "Penrose triangle" suggests a ratio of about 65,000 vs. 10,000.

"Penrose triangle" is also slightly confusing because although the thing is basically triangular it isn't a literal triangle, and because Penrose is now associated with Penrose tiling, which he did invent, and which does tend to involve real triangles. Make "tribar" the primary name and "P-t" a secondary name, but keep all the Penrose info, and the Penrose polygons as good supplementary info? ErkDemon 01:02, 21 June 2007 (UTC)

better picture

this is a better impossible triangl picture!File:Imposible shape 3

Here is a moving image of a Penrose Triangle: https://www.facebook.com/100009344523684/videos/764913091656665 — Preceding unsigned comment added by 69.121.228.77 (talk) 19:29, 13 December 2023 (UTC)

better picture

this is a better impossible triangl picture!File:Imposible shape 3.jpg

Possible?

http://www.coolopticalillusions.com/build-an-impossible-triangle.htm Mwv2 05:32, 29 October 2007 (UTC)

Link appears to be dead. SheffieldA (talk) 12:16, 5 September 2021 (UTC)

Proposed image change.

I really found the Penrose polygons interesting, but I thought the images were a bit confusing. I thought the effect would be much clearer if a few of the lines removed and the "sides" color coded (as in Image:Penrose triangle.svg), so I made svg images based on the current images, but with those changes. I also changed the rectangle to a square because I felt a regular polygon would fit in with the other examples better, and rotated it 45 degrees because I felt that increased the resemblance to Image:Penrose triangle.svg. I used the same licenses for each as on the current images.

• 
  Penrose square
• 
  Penrose pentagon
• 
  Penrose hexagon
• 
  Penrose octagon

If there are no reasonable objections in the next week I will go ahead and replace the current images.

Trilink 02:49, 2 December 2007 (UTC)

There being no objections, I have made the change. Trilink (talk) 03:45, 10 December 2007 (UTC)

• Looks great. Well done - Gobeirne (talk) 03:48, 10 December 2007 (UTC)

Austrian impossible tribar sculpture - explanation?

There is no explanation offered for the Austrian impossible tribar sculpture in the article, and it is rather confusing tot ry to figure out how it exists. It does not appear to be disjointed, and I examined the image provided in the "links" section as well (which is from a slightly different angle). There really should be something in the way of clarifying how that particular illusion works. 216.82.142.13 (talk) 19:45, 18 March 2009 (UTC)

Check out the description on the image's page at Image:ImpossibleTriangleEastPerth_edit_gobeirne.jpg. Doctorfluffy (robe and wizard hat) 20:05, 18 March 2009 (UTC)

The question is not answered. "Austrian" and "Australian" relate to two different sculptures in two separate continents. Snezzy (talk) 16:35, 29 August 2011 (UTC)

Given the existence of the wood sculptue from Austria and the stainless steel piece from Germany, this may not belong in the category of "impossible" shapes. Likewise the square, hexagon, etc. SheffieldA (talk) 12:18, 5 September 2021 (UTC)

Inspired by M. C. Escher?

How can the Penrose triangle be inspired by M. C. Escher, when it was created in 1934, while Escher's first impossible print was published in 1937? -- Jsdo1980 (talk) 11:20, 17 May 2009 (UTC)

Two people independently "discovered" it at different times. The latter of which was inspired by Escher. Doctorfluffy (robe and wizard hat) 16:51, 17 May 2009 (UTC)

Escher didn't draw impossible objects at all, or at least none that I've seen. Escher's drawings were only of physical oddities, many of which would require some special way of defying gravity or being in space or something, but all the ones I've seen could be built without any optical illusions. (KS57 (talk) 13:14, 18 August 2010 (UTC))

Build this then: Image:Escher Waterfall.jpg --TheSane (talk) 10:21, 19 February 2011 (UTC)

Copyright violation

It seems that Ulrich Schwanitz the designer of the 3D penrose pictured, DMCAed the thingiverse link calling it an infringement of his copyright. List of things I found:

• Ulrich is German [1]

this search proves nothing. In the thingiverse comments there is a post about Mr. Schwanitz beeing from the Netherlands, which is possible but again unproven. IMHO it doesnt matter, though. --0x6d64 (talk) 10:49, 19 February 2011 (UTC)

• DMCA and Thingiverse is Amercian, does it apply to German deisgns?
• The version of the Penrose trianlge Ulrich used was by Oscar_Reutersvärd [2]
• Ulrich's 3D model was derivative of this Swedish designer's illustration
• The Thingiverse designer worked from scratch to create a derviative that was also printable [3]
• All this is bad mojo of people making derivatives and not actual infringement.

Alas, the Thingiverse link is down [4] Eagleapex (talk) 20:23, 18 February 2011 (UTC)

Use your favorite firefox plugin to search caches. --0x6d64 (talk) 10:49, 19 February 2011 (UTC)

I don't suppose any of you thingiverse folks noticed that he put "The design files for this model have now been released to the public domain" on his page, linking to the design files? He's given up copyright on it. How does someone file a DMCA takedown notice on an item they've released to the public domain? Permalink at http://www.webcitation.org/5wfT4qTPT 12.186.80.1 (talk) 17:35, 21 February 2011 (UTC)

Update: He retracted his DMCA takedown notice and put it up as public domain as detailed here: http://blog.thingiverse.com/2011/02/21/a-change-of-triangular-heart/ —Preceding unsigned comment added by 72.16.130.198 (talk) 18:27, 21 February 2011 (UTC)

Let's all rejoice another win for Public Domain! -Eagleapex (talk) 19:28, 7 March 2011 (UTC)

Experience

It's possible,by is optical ilussion and cappable to build. — Preceding unsigned comment added by 188.26.250.159 (talk) 18:48, 21 January 2014 (UTC)

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Why is there a reference to the "Penrose square root law" here? It is totally unrelated to the topic of this page. (Aaron Sloman) — Preceding unsigned comment added by 77.102.46.107 (talk) 21:43, 17 July 2019 (UTC)

Possible graffiti and/or hoax image

The image "A 3D-printed version of the Reutersvard Triangle illusion" appears to me to have been heavily doctored. A close look suggests a hand-drawn Reutersvard triangle may be Photoshopped into a photo of a posed hand holding something else. Can a reliable source be found to back up the "3D-printed" claim? Shadowing and exposure, particularly where the triangle meets the hand, are rather incongruous with the rest of the photo. Public fascination with 3-D printers, combined with public ignorance about their limitations and capabilities, would seem to create a fertile environment to hoax folks into believing 3-D printers produce impossible objects. There was no way I could verify the caption's claim that the triangle in the image is a 3-D printed object because I couldn't find any other images of it from the same author besides the heavily posed picture someone included in this article (and others?)106.1.65.224 (talk) 00:13, 27 April 2018 (UTC)