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But there's a solution where the camera is in a general position. See this thread: https://news.ycombinator.com/item?id=29877311 https://news.ycombinator.com/i

by SilasX 5y ago

But there's a solution where the camera is in a general position. See this thread: https://news.ycombinator.com/item?id=29877311 https://news.ycombinator.com/item?id=29877311

Jtsummers 5y ago
Which I was also in, just look at Huffman's paper, it's not that long, which lays out his various assumptions which lead to why the figure would be an impossible pyramid. That it has a valid interpretation does not make it suddenly a possible pyramid just a possible polyhedron, if you introduce information that isn't evident in the image. There's no sense in discussing Huffman's Impossible Pyramid without also considering Huffman's definition for impossible. If we discard his definition, what we're talking about is something else entirely.
- SilasX 5y ago
  Sure, and I addressed your point there[1], that this still requires a non-standard, new definition of "impossible figure". Furthermore, I don't see how it introduces information that "isn't evident in the image" when several people automatically assumed a 4 sided base (me among them) without trying to be clever. [1] https://news.ycombinator.com/item?id=29879862 https://news.ycombinator.com/item?id=29879862
  - Jtsummers 5y ago
    "assumed", because it wasn't presented. It wouldn't need to be assumed if it were present. That's pretty much the definition of assuming.
    - SilasX 5y ago
      It's "assumed" only in the sense that the form of any occluded part of an image is "assumed". By that standard, "ACFD is a face/plane" isn't presented either, and, relative to the image alone, is "assumed" in the same sense.
      - Jtsummers 5y ago
        Again, I'm not saying that this blog post presented the problem statement effectively. That is literally why I linked the original. So that we don't have to assume anything about what Huffman meant in his formulation because he stated his assumptions and definitions. I'm only saying that given Huffman's formulation it is an impossible pyramid. All the other possible "solutions" are not solutions to how this can be a pyramid, instead they are solutions to how it can be something else. Which is covered in Huffman's paper, which you apparently cannot be bothered to read. To summarize: If this were a real image of a real object, then it is, by definition, a possible object, but it is not, per the image, a possible pyramid. The camera would have to be shifted (or lighting altered or something changed) in order to discern what it actually was (which could be a pyramid if some distortion were discovered, but could also be any of a number of other possible objects, including, as one person suggested, the corner of a room through a peculiarly shaped viewport).

by SilasX 5y ago

But there's a solution where the camera is in a general position. See this thread: https://news.ycombinator.com/item?id=29877311 https://news.ycombinator.com/item?id=29877311

Jtsummers 5y ago

Which I was also in, just look at Huffman's paper, it's not that long, which lays out his various assumptions which lead to why the figure would be an impossible pyramid. That it has a valid interpretation does not make it suddenly a possible pyramid just a possible polyhedron, if you introduce information that isn't evident in the image. There's no sense in discussing Huffman's Impossible Pyramid without also considering Huffman's definition for impossible. If we discard his definition, what we're talking about is something else entirely.

SilasX 5y ago
Sure, and I addressed your point there[1], that this still requires a non-standard, new definition of "impossible figure". Furthermore, I don't see how it introduces information that "isn't evident in the image" when several people automatically assumed a 4 sided base (me among them) without trying to be clever. [1] https://news.ycombinator.com/item?id=29879862 https://news.ycombinator.com/item?id=29879862
- Jtsummers 5y ago
  "assumed", because it wasn't presented. It wouldn't need to be assumed if it were present. That's pretty much the definition of assuming.
  - SilasX 5y ago
    It's "assumed" only in the sense that the form of any occluded part of an image is "assumed". By that standard, "ACFD is a face/plane" isn't presented either, and, relative to the image alone, is "assumed" in the same sense.
    - Jtsummers 5y ago
      Again, I'm not saying that this blog post presented the problem statement effectively. That is literally why I linked the original. So that we don't have to assume anything about what Huffman meant in his formulation because he stated his assumptions and definitions. I'm only saying that given Huffman's formulation it is an impossible pyramid. All the other possible "solutions" are not solutions to how this can be a pyramid, instead they are solutions to how it can be something else. Which is covered in Huffman's paper, which you apparently cannot be bothered to read. To summarize: If this were a real image of a real object, then it is, by definition, a possible object, but it is not, per the image, a possible pyramid. The camera would have to be shifted (or lighting altered or something changed) in order to discern what it actually was (which could be a pyramid if some distortion were discovered, but could also be any of a number of other possible objects, including, as one person suggested, the corner of a room through a peculiarly shaped viewport).