<p>Assuming your optimal viewing angle is parallel to the surface of the display and the pyramid is made from faces that are 45 degrees to its virtual (non-existant) base, it's actually just a simple non-transformed image (besides the reflection).</p>

<p>1:1 projection. No transformations. No scaling. </p>

CC BY-SA 3.0
2015-08-09T09:12:03.990Z
For more information, see [Pepper's Ghost](https://en.wikipedia.org/wiki/Pepper's_ghost)
Mark
CC BY-SA 3.0
2015-08-10T15:19:01.417Z
Its an interesting comment about Pepper's ghost. Notice that Pepper's ghost was originally a reflection of a 3D object so the reflection itself was 3D. In the case of these popular device based projections, the projections are only 2D so the effect is only a 2D reflection suspended in space. The most popular Youtube videos meant for doing this don't even have 4 different perspectives, just 1 repeated 4 times.
Octopus
CC BY-SA 3.0
2015-08-04T20:08:24.347Z
2015-08-04T20:08:24.347Z
Octopus
<blockquote>
  <p>I was wondering, given a model, which transformations I should apply to get the different projections needed to produce this effect?</p>
</blockquote>

<p>There are at least 2 types of videos and many ways to produce them. It is technically correct to call this effect <a href="https://en.wikipedia.org/wiki/Pepper%27s_ghost" rel="nofollow noreferrer">Pepper's ghost</a> but you will obtain more relevant search results by searching for: "<a href="https://www.google.com/search?ei=OLGhW9ScGtq50PEP0LWyiAY&amp;q=Smartphone%203D%20Hologram" rel="nofollow noreferrer">Smartphone 3D Hologram</a>" (over 2 million hits).</p>

<p>To make the projector you'll need: graph paper, CD case, marker or pen, pair of scissors, Cellotape and/or superglue, craft knife or glass cutter, and a smartphone or computer monitor.</p>

<ol>
<li><p>Draw one side of a square <a href="https://en.wikipedia.org/wiki/Frustum" rel="nofollow noreferrer">frustum</a> on graph paper and cut out 4 shapes from a CD case.</p></li>
<li><p>Tape and/or glue them together and place it top down on the center of your cellphone screen.</p></li>
</ol>

<p><a href="https://i.sstatic.net/pHNay.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/pHNay.png" alt="Holographic Smartphone Projector"></a></p>

<p>To make videos there are two kinds to choose from, one image rotated 90° and repeated, or four different images representing each side of the image. Whichever style is chosen each image is placed in a quadrant around the center of the screen.</p>

<p>Use this for a template:</p>

<p><a href="https://i.sstatic.net/NuZ2P.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/NuZ2P.jpg" alt="Holographic Template"></a></p>

<p>To make the simple rotated image use a program such as <a href="http://www.avs-plus.net/" rel="nofollow noreferrer">AVISynth</a> or PowerDirector, load the video into the Timeline, add a grid, duplicate the track 3 times, rotate each track 90° and place it in one of the quadrants.</p>

<p><a href="https://i.sstatic.net/dOJ3t.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/dOJ3t.jpg" alt="4 Videos, rotated 90°"></a></p>

<p>The second type of video is produced from 4 seperate images each rotated 90°, this provides a different view from each side. It's difficult to produce a live video of this type, align everything perfectly, and not get the opposing cameras in each other's shot. It's easier to create an animation for this purpose. It should look like this:</p>

<p><a href="https://i.sstatic.net/mySpZ.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/mySpZ.png" alt="Dancing Girl"></a></p>

CC BY-SA 4.0
2018-09-19T04:14:12.783Z
2018-09-19T04:14:12.783Z
Rob
<p>I saw a <a href="https://www.youtube.com/watch?v=7YWTtCsvgvg" rel="noreferrer">video</a> on YouTube where a person uses a transparant, knotted pyramid to display "holograms" using their smartphone. (I have not been able to reproduce this yet, so I can't tell for sure if it works).</p>

<p>I was wondering, given a model, which transformations I should apply to get the different projections needed to produce this effect?</p>

CC BY-SA 3.0
2015-08-07T16:13:30.893Z
Please don't call these optical tricks "holograms". Refer to the "[Things often confused with holograms](https://en.wikipedia.org/wiki/Holography#Things_often_confused_with_holograms)" for an overview. In this case, you're talking about a classic [Pepper's ghost](https://en.wikipedia.org/wiki/Pepper%27s_ghost) illusion. No 3D at all, apart from having 4 different perspectives. **update:** I've proposed an edit to adjust the question accordingly.
waldyrious
<projections><transformations>
What transformations should I apply to a model to produce this 3D effect?
S.L. Barth is on codidact.com
# What transformations should I apply to a model to produce this 3D effect?

(Asked by: username_0 on 2015-08-04)

I saw a [video](https://www.youtube.com/watch?v=7YWTtCsvgvg) on YouTube where a person uses a transparant, knotted pyramid to display "holograms" using their smartphone. (I have not been able to reproduce this yet, so I can't tell for sure if it works).

I was wondering, given a model, which transformations I should apply to get the different projections needed to produce this effect?

**Tags:** projections, transformations

> **Comments:**
> **username_1**: Please don't call these optical tricks "holograms". Refer to the "[Things often confused with holograms](https://en.wikipedia.org/wiki/Holography#Things_often_confused_with_holograms)" for an overview. In this case, you're talking about a classic [Pepper's ghost](https://en.wikipedia.org/wiki/Pepper%27s_ghost) illusion. No 3D at all, apart from having 4 different perspectives. **update:** I've proposed an edit to adjust the question accordingly.  

---

## 2 answers

### Answer by username_2 on 2015-08-04. Score: 5

Assuming your optimal viewing angle is parallel to the surface of the display and the pyramid is made from faces that are 45 degrees to its virtual (non-existant) base, it's actually just a simple non-transformed image (besides the reflection).

1:1 projection. No transformations. No scaling.

> **Comments:**
> **username_3**: For more information, see [Pepper's Ghost](https://en.wikipedia.org/wiki/Pepper's_ghost)  
> **username_2**: Its an interesting comment about Pepper's ghost. Notice that Pepper's ghost was originally a reflection of a 3D object so the reflection itself was 3D. In the case of these popular device based projections, the projections are only 2D so the effect is only a 2D reflection suspended in space. The most popular Youtube videos meant for doing this don't even have 4 different perspectives, just 1 repeated 4 times.  

---

### Answer by username_4 on 2018-09-19. Score: 1

> I was wondering, given a model, which transformations I should apply to get the different projections needed to produce this effect?

There are at least 2 types of videos and many ways to produce them. It is technically correct to call this effect [Pepper's ghost](https://en.wikipedia.org/wiki/Pepper%27s_ghost) but you will obtain more relevant search results by searching for: "[Smartphone 3D Hologram](https://www.google.com/search?ei=OLGhW9ScGtq50PEP0LWyiAY&q=Smartphone%203D%20Hologram)" (over 2 million hits).

To make the projector you'll need: graph paper, CD case, marker or pen, pair of scissors, Cellotape and/or superglue, craft knife or glass cutter, and a smartphone or computer monitor.

1. Draw one side of a square [frustum](https://en.wikipedia.org/wiki/Frustum) on graph paper and cut out 4 shapes from a CD case.
2. Tape and/or glue them together and place it top down on the center of your cellphone screen.

[![Holographic Smartphone Projector](https://i.sstatic.net/pHNay.png)](https://i.sstatic.net/pHNay.png)

To make videos there are two kinds to choose from, one image rotated 90° and repeated, or four different images representing each side of the image. Whichever style is chosen each image is placed in a quadrant around the center of the screen.

Use this for a template:

[![Holographic Template](https://i.sstatic.net/NuZ2P.jpg)](https://i.sstatic.net/NuZ2P.jpg)

To make the simple rotated image use a program such as [AVISynth](http://www.avs-plus.net/) or PowerDirector, load the video into the Timeline, add a grid, duplicate the track 3 times, rotate each track 90° and place it in one of the quadrants.

[![4 Videos, rotated 90°](https://i.sstatic.net/dOJ3t.jpg)](https://i.sstatic.net/dOJ3t.jpg)

The second type of video is produced from 4 seperate images each rotated 90°, this provides a different view from each side. It's difficult to produce a live video of this type, align everything perfectly, and not get the opposing cameras in each other's shot. It's easier to create an animation for this purpose. It should look like this:

[![Dancing Girl](https://i.sstatic.net/mySpZ.png)](https://i.sstatic.net/mySpZ.png)


---

