
Pepper's Cone: An Inexpensive Do-It-Yourself 3D Display - lainon
https://roxanneluo.github.io/PeppersCone.html
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jacinabox
Something similar to this effect was demonstrated in a do-it-yourself project
on Youtube:

[https://www.youtube.com/watch?v=fggE3VI3NRg](https://www.youtube.com/watch?v=fggE3VI3NRg)

The device described in the paper seems to be superior to that shown at the
link, because it uses a cone shaped display apparatus instead of a pyramidal
one. The pyramidal display allows for only three distinct views, whereas the
cone-shaped one allows for a continuously varying viewpoint.

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jacinabox
Correction, reading further I see that the linked paper describes using a
gyroscopic sensor to dynamically vary the viewpoint as the user rotates the
device, but it remains true that the conic apparatus can display an image to
be viewed comfortably from any angle.

Based on these considerations I propose an additional enhancement. Using the
well understood technology of privacy filters for laptops, it could be
possible to effectively occlude views based on orientation, allowing for the
display of several views of a scene simultaneously, with the one visible
depending on the user's orientation with the device.

~~~
JKCalhoun
> using a gyroscopic sensor to dynamically vary the viewpoint as the user
> rotates the device

Yes, this is what occurred to me when watching the video. It must know if it
being rotated. For the tiger to be seen on the side of the cone you are
viewing, it needs to be rendered on the display somewhere between the "nickel"
and the viewer.

Someone viewing from the opposite side of the cone would not see the
reflection that you are seeing — no tiger on their side of the cone. (Now, in
that specific case, two viewers 180 degrees apart, you could in fact render
two tigers on opposite sides of the code so both viewers see a tiger.)

No true stereo at all though with the cone. Left and right eye will see the
same tiger. Only a sort of "perceived" stereo if you rotate the device.

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Turing_Machine
> No true stereo at all though with the cone.

The video shows them using anaglyphs for this.

Presumably shutter glasses could also be used if you wanted better color
rendition.

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thomastjeffery
Polarized glasses could also work.

~~~
colordrops
I don't think any tablets have the ability to selectively emit polarized
light.

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pbhjpbhj
Just in case it's your moment to learn about it,
[https://en.wikipedia.org/wiki/Pepper%27s_ghost](https://en.wikipedia.org/wiki/Pepper%27s_ghost)
is presumably the origin of the name.

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mchlgyr14
I would like to be notified when the source code is available. I'm interested
in trying to develop video format for Pepper's cone. thanks.....My name is
Michael and my email address is mchlgyr14 @gmail.com

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dvt
Unfortunately, this only works from a _specific angle_ , as the calibration
needs to take viewer perspective into consideration. They criticize the more
standard Pepper's Ghost and its "undesirable seams and [...] difficult[ty] to
fuse at oblique viewing angles" \-- but their project has _no_ viewing angles.
It's basically a 2D plane because your head and eyes _must_ remain stationary
(but the iPad can spin).

~~~
Terretta
On the contrary, last few seconds of video demonstrate a pretty wide viewing
range.

The range shown looks comparable to low quality LCDs before off axis causes
color shift. People accept those LCDs, seems that angle would be plenty for
this purpose since they also let you (appear to) spin the object.

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teraflop
This is a "3D display" in the same sense that a curved monitor is a "3D
display" because it exists in three-dimensional space. The actual image being
displayed is two-dimensional (ignoring the red-blue anaglyph gimmick).

I think it would be more accurate to just call this a transparent heads-up
display.

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throwaway2048
you dont technically see in 3d either, you see 2 2d projections, so this is
pretty silly pedantry.

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TheRealPomax
Not really.

We don't "see" with our eyes, we see with our brain, based on input received
from the eyes. The brain itself is perfectly capable of constructing a 3D
representation based on the two planar projections that are registered by the
eyes.

What makes something 3D, rather than 2D or 2.5D, is that it can be observed
from different angles by multiple observers at the same time. It's a fairly
trivial test, and this fails it. That doesn't mean its not cool, but it does
mean it's not 3D and calling it 3D is plain wrong. Especially when it's
something you're publishing a paper about in a scientific publication. This is
instead exactly as was commented on: a curved "monitor" that happens to be
calibrated to only _seem_ 3D exactly at a single viewing angle, for a single
observer, similar to Pepper's Ghost (which only works properly when viewers
are positioned at a specific angle to the glass pane).

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fezz
Practially speaking, this doesn't add anything you couldn't do by rotating the
model on the ipad... other than transparency but an opaque reflective sheet
would work just the same.

~~~
xuanluo
The whole idea here is to achieve convincing 3D illusion. To achieve that you
need to achieve approximate enough 3D cues. With opaque reflector, the
occlusion cues is contradicting with the effect we want to achieve. We want
the object to float inside, but the occlusion tells you that the object is in
front of the cone. Transparency, the parallax you can see between the object
and the background and feeling of co-presence all add magic to the final
illusion of 3Dness.

~~~
ChuckMcM
Excellent work btw. I love the simplicity of the display construction. I'm
curious to see what it would look like scaled up to a 32" 4K display as the
'base'.

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nyreed
I'm not sure I understand where the gyroscope comes in. Is he saying the
warped image on the LCD changes as the iPad rotates? Does that mean two people
sitting on opposite sides of the cone are seeing the same image?

~~~
julianj
My understanding from the video is that only one perspective is rendered at a
time. This perspective is rendered on only one side of the cone at a time. It
makes more sense when you can see the image from the iPad. Check out the
video[1] at 2:37 and 3:10.

[1] [https://youtu.be/W2P-suog684?t=157](https://youtu.be/W2P-suog684?t=157)

~~~
alok-g
So if I understand correctly, the viewer would need to position herself
correctly. Also, shouldn't this need compass sensor instead of gyro?

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nyc
When I have some time, I plan to implement it myself for fun & learning. It's
a cool effect and the linked paper provides enough detail for others to build
something similar. I think building it would be a good exercise for learning
about camera APIs, projection mapping (i.e. pre-distorting things so that when
they are projected they look undistorted) and writing fragment shaders. When
the code gets posted, I think it'll be even more educational.

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bane
Not terribly different from the old Sega "Hologram" games
[https://www.youtube.com/watch?v=Y-SuK5-cKk0](https://www.youtube.com/watch?v=Y-SuK5-cKk0)

 _edit_

Some thoughts after watching the video. This is way cooler. Since the
reflector is transparent, you could put a kinect-like camera in the center
(something with depth mapping) -- pointed at the viewer. With some head
tracking to "rotate" the display, a reasonable 3d face-to-face chat system
wouldn't be impossible since both sides could "see" a 3d representation of the
other side, and the gazes of both parties could be looking naturally at the
eyes of the other participant (if the camera is eye level).

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rrauenza
I'd seen this before:

[http://www.instructables.com/id/Turn-cell-phone-and-
tablet-i...](http://www.instructables.com/id/Turn-cell-phone-and-tablet-
in-3D-hologram/)

..but it uses a prism shape, not a cone.

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pbhjpbhj
Mentioned in the video of the OP at 38s+.

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jingjuliawang
It is so cool to implement 3D illusion with such simple equipments. I expect
more exciting works by the authors, like human-size 3D illusion with same cost
of display construction.

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jamessb
It would be better for the link to point at the project homepage [1], as this
also includes an explanatory video (the current submission is the PDF of the
paper).

[1]:
[https://roxanneluo.github.io/PeppersCone.html](https://roxanneluo.github.io/PeppersCone.html)

~~~
dang
Ok! Changed from [http://grail.cs.washington.edu/wp-
content/uploads/2017/10/lu...](http://grail.cs.washington.edu/wp-
content/uploads/2017/10/luo2017pca.pdf). Thanks.

~~~
xuanluo
And the video
[https://www.youtube.com/watch?v=W2P-suog684&feature=youtu.be](https://www.youtube.com/watch?v=W2P-suog684&feature=youtu.be)
:)

