Thanks to the effects of Kdenlive we can build a hologram, like those seen in all the greatest science fiction films. All we need is a video of who will represent the hologram in front of a green sheet.
In all science fiction films set in a more or less remote future, various futuristic objects are seen, such as teleportation devices or telecommunications with holograms. In fact, it is often difficult for current writers to imagine what the world will be like and what technology we will have between dozens and dozens of years: if for the authors of Back to the future we should all have flying cars but no flat-screen TVs, it is obvious that to do forecast is not easy. But holograms are something actually realistic, more than anything else, because they already exist: they are only very expensive, and it seems that for now only one of the candidates for the French presidency could afford them (Melenchon, who led a demonstration in two cities simultaneously thanks holograms). But it is likely that over the next few decades the price will drop and it will be possible to make 3D video calls. In other words, even if at the moment the “domestic” holograms are still science fiction, they are not such an unrealistic forecast, and they can prove to be an excellent idea for those who want to make a science fiction film that has a background of truth. Inserting a fake hologram in one of our videos is a not too complicated operation, but requires some precautions. First of all, you will need a movie of the “original” scene, that is, the one where you see the hologram projector: this movie will function as the background of the effect. Another film will be positioned above this background, the one that will represent the hologram itself: simply a shot of our actor in front of a green cloth. With the “chromatic key” effect we can make the green cloth disappear, perfectly superimposing the actor on the background, as if it were coming out of the projector. However, it is obvious that a simple overlay cannot be enough: first of all, we will have to use a light-type overlap mode, in particular “Hard light” is recommended. In this way the hologram will appear to be made up of light, therefore like a real hologram. To facilitate the idea that the hologram comes from the projector, we can draw light rays, to appear (weak, of course) like a cone that comes out right from the projector and that surrounds the hologram. In addition, we will have to add some noise: if the image is too perfect, it is not realistic. Partly because of the mistrust that everyone has towards telecommunications providers, partly because of the awareness that perfect things don’t exist, nobody expects a hologram to really look like having a person in front of him. With Kdenlive we can add two disturbances to make the hologram more realistic: first of all the “grain” effect, that is, a random disturbance of points that appear on the hologram as a sort of rustling of the image. They give the impression that the hologram is actually made up of dots of light. The other effect is called “wave”, and it is a series of waves (which we will set in a horizontal position, to simulate the classic line scan, typical of old cathode ray tube televisions. In fact, holograms work just like a projection, therefore it is intuitive for the public to imagine that any interference in the signal results not as a pixxelated image (as with digital televisions), but as a deformation of the wave-shaped image. As always, you can see the video example at the following address: https://www.youtube.com/watch?v=IhR7XwU0dmI
The right point of view
There are some small tricks that can be taken during filming to make the illusion of using a holographic projector the best. First of all, it is good to choose a “normal” lens, for example a 50mm lens on a full frame video camera, so that the image appears as natural as possible. Then, it is a good idea to shoot the actor from below, therefore positioning the camera at maximum half a meter from the ground, because the observation point is always expected to be low. However, if you plan to “project the hologram” from a raised point, such as the ceiling, then you have to take the shot in reverse, from a very high point. In both cases, the forced perspective could make shooting difficult, but just turn the camera 90 degrees and shoot using the longer side of the sensor. The image can then be rotated with the effect Rotate and shear in Kdenlive.
Choose a frame from the projector
We select a frame from the original video where we see what the holographic projector will look like
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Some changes with GIMP
We use the photo editing program to draw light rays from the projector
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Overlapping clips
We use Kdenlive to superimpose the “hologram” actor on the light rays and on the original clip
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The image becomes a hologram
By applying a couple of effects, the actor’s video clip can look like a hologram
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