Can You Spot the Invisible Ductwork?

[russ_watters]

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...]

 

[Gokul43201]

I'm confused. Are we talking about an existing duct that is occupying the location pointed out by the red sketch?

 

[russ_watters]

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.

 

[BobG]

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


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).

 

[FredGarvin]

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

 

[Gokul43201]

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...

 

[Pengwuino]

Yah i have no idea what's going on here

 

[russ_watters]

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.

 

[russ_watters]

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.

 

[FredGarvin]

NOW I see it. The red outline in the original picture made it hard for me to see.

 

[Cyrus]

It's like magic.

 

[Pengwuino]

Yah i see it too now that the red lines are gone

 

[chroot]

Wow, that is pretty weird!

- Warren

 

[Pengwuino]

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.

 

[Kalimaa23]

This is why I never trust engineers...

 

[Mattara]

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.

I still don't see it.

Anyone care to do some paint magic?

 

[wolram]

Good joke Russ,i wonder how many fell for it

 

[Cyrus]

It's not a joke, its really there.

 

[wolram]

Hmmm, and you can see that pipe through it and all the other details, yeah right

 

[Cyrus]

I am not joking wolram. Look at the two pictures and it will sink in.

 

[Gokul43201]

Wollie, the electrical conduit, the big PVC pipe, the water lines and the Unistrut support running perpendicular to them, all lie below the duct. That's why you can see them.

 

[Danger]

That is one freakish picture, alright. It's like watching a boring version of 'Predator'.

 

[DaveC426913]

Whoa. Good illusion.

Now, to be fair, you've "enhanced" the illusion. You've drawn in some thick "trees" that cover the "forest" and then asked if we can see the forest...

:-)

 

[Moonbear]

Wow, that's pretty cool. Even when I know where it is (I had picked up on the blur as a reflection too, but still couldn't see how it was a duct) I can't see it with the lines there. The line obscures the edge, and with the angle just right that the reflection of the beam is continuous with the line of the beam itself, well, that's just really cool!

 

[Cyrus]

Better than the man with the open brain, eh Moonbear?

 

[Moonbear]

Better than the man with the open brain, eh Moonbear?

Yep, at least this one came with the solution.

 

[russ_watters]

Whoa. Good illusion.

Now, to be fair, you've "enhanced" the illusion. You've drawn in some thick "trees" that cover the "forest" and then asked if we can see the forest...

:-)

Ya, but the point is that I did that to show the duct, not to hide it. My honest attempt to clarify it ironically had the opposite effect.

 

[chroot]

Wow, that's pretty cool. Even when I know where it is (I had picked up on the blur as a reflection too, but still couldn't see how it was a duct) I can't see it with the lines there. The line obscures the edge, and with the angle just right that the reflection of the beam is continuous with the line of the beam itself, well, that's just really cool!

Open both pics up in separate browser windows, then switch back and forth.

- Wqarren

 

[Moonbear]

Open both pics up in separate browser windows, then switch back and forth.

- Wqarren

HEYYYYYYYYY! Somebody was fiddling with brightness and contrast settings!

 

[darkar]

Well, i think because of the first pic with red lines, not only red lines was added, but the whole picture has been made gray as well. So the difference between background and foreground isn't so obvious. It is like u looking behind a blur lens. But look at the second picture the shadow of the edge due to the light(probably flash in this case) marks the edge sharply than the first one. And first picture look very dull and 2D, whereas second one looks much realistic, 3D and defined.