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Invisible Ductwork?

  1. Jul 25, 2006 #1

    russ_watters

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    No, it isn't a new invention, it's an optical illusion. I was discussing a new ductwork design for an existing (recently renovated) building with my boss. I needed to clarify something, so I printed out the attached picture and sketched-in the duct, roughly like I have it sketched in the attachment. My boss looked at it and said 'you're nuts - there's no duct in that picture!' Looking back at the picture, I had to agree, but dang - I knew there had to be a duct there. And there is. It took me a few minutes to figure it out, but it is there. Trust me.

    So do you see it?

    Hint: It is drawn in correctly, but keep in mind that much of it is behind other objects and you can only see one side face and a little bit of the bottom.

    [The attached photo has its contrast lowered to better match the draft quality I showed my boss. I'll post the regular quality image with no sketched-in outline later...]
     

    Attached Files:

    Last edited: Jul 25, 2006
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  3. Jul 25, 2006 #2

    Gokul43201

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    I'm confused. Are we talking about an existing duct that is occupying the location pointed out by the red sketch?
     
  4. Jul 25, 2006 #3

    russ_watters

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    Yes, there is an existing duct that is shown in the image, and I have outlined it. Keep in mind, the outline covers the entire duct, not just the part of the duct that is visible. Your view of some of the duct is blocked by objects.
     
    Last edited: Jul 25, 2006
  5. Jul 25, 2006 #4

    BobG

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    How can you not see it? It's the red thing, right? :uhh:


    Okay, I take it the reason part of the ceiling is fuzzy is because it's actually a reflection off of the duct work? (You can almost make out the reflection of the two knotholes).
     
  6. Jul 25, 2006 #5

    FredGarvin

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    Perspective is killing me on this. I can't see anything. To help clarify, what side of the duct is visible?
     
  7. Jul 25, 2006 #6

    Gokul43201

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    I'm completely stumped...despite staring at the possible reflection off a side wall (as pointed out by BobG). This is one crazy neat picture!

    PS : Also, if you look along the left red line defining the bottom edge, you see some diffuse bluriness right down its length...
     
    Last edited: Jul 25, 2006
  8. Jul 25, 2006 #7

    Pengwuino

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    Yah i have no idea what's going on here
     
  9. Jul 25, 2006 #8

    russ_watters

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    My boss had an advantage - he knew exactly what he was looking at because we had a bunch of drawings in front of us. But he still couldn't see it. He simply thought the picture was taken before the duct went in.

    The beige object on the right with the sheet-metal covering it is the rear-end of the HVAC unit. The duct is above and to the left of it. The duct is 12" high and you have an almost unrestricted view of about 3' of the right side of the duct (and the entire 12" high) - the only thing in front of (below) it is that piece of uni-strut that is supporting the pipes. You can also see perhaps an inch of the bottom along that 3' with the rest covered from below by the pipes.

    Bob is right: the duct is reflective enough and the angle of the reflection is such that it just looks like the ceiling joists and plywood above continue on from right to left until they hit the pipes. You can see that the joists aren't exactly straight between the red lines. One of my coworkers said it looked like someone spilled water on the picture.
     
    Last edited: Jul 25, 2006
  10. Jul 25, 2006 #9

    russ_watters

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    Here is the original. Without the outline, the bottom right edge of the duct is clear and the flash casts a thin shadow on the ceiling above the top right edge, making that visible as well. So when I outlined the duct for you guys and my boss, though I actually did it to show exactly where the duct was, I took away the features that made it visible, and it disappeared. And the lower contrast of the draft printout (and my simulation of it) makes it tougher to see that the reflection is, in fact, a reflection.

    FYI, the point of printing this out was to double-check the clearance above the duct. I hadn't written it down becase the duct is right up against the joists.
     

    Attached Files:

  11. Jul 25, 2006 #10

    FredGarvin

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    NOW I see it. The red outline in the original picture made it hard for me to see.
     
  12. Jul 25, 2006 #11
    It's like magic.
     
  13. Jul 25, 2006 #12

    Pengwuino

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    Yah i see it too now that the red lines are gone
     
  14. Jul 25, 2006 #13

    chroot

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    Wow, that is pretty weird!

    - Warren
     
  15. Jul 25, 2006 #14

    Pengwuino

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    It's not weird when you get rid of hte red lines. It was obvious something was going on with the blur, its just that the critical lines were covered by the red lines russ drew.
     
  16. Jul 25, 2006 #15
    This is why I never trust engineers...
     
  17. Jul 25, 2006 #16
    I still don't see it. :uhh:

    Anyone care to do some paint magic? :rofl:
     
  18. Jul 25, 2006 #17

    wolram

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    Good joke Russ,i wonder how many fell for it :biggrin:
     
  19. Jul 25, 2006 #18
    It's not a joke, its really there.
     
  20. Jul 25, 2006 #19

    wolram

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    Hmmm, and you can see that pipe through it and all the other details, yeah right :tongue2:
     
  21. Jul 25, 2006 #20
    I am not joking wolram. Look at the two pictures and it will sink in.
     
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