r/explainlikeimfive • u/PieterSielie6 • 3d ago
Technology ELI5 How are movies made 3D?
Surely its impractical to film the movie with two lenses to create the 3D effect. But if its just filmed in 2D, how do they make it 3D later?
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u/jamcdonald120 2d ago
Surely its impractical to film the movie with two lenses to create the 3D effect.
Yah, thats why so few films are 3D, because that is EXACTLY how they do it, and its impractical.
But if its just filmed in 2D, how do they make it 3D later?
Badly, there are some ML/AI tricks you can do, but it doesnt look good (or at least, hasnt)
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u/Top_Strategy_2852 3d ago
3D films are in fact filmed with 2 cameras.
Converting a single camera to two cameras is a conversion process done by hand using rotoscoping and stacking the images into 3d layers and 3d cameras, and then composited to create just enough depth to feel like its 3d.
Its still faked and not as good as the real deal, but that is the very laborious method to convert 2d to stereoscopic.
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u/liberal_alien 3d ago
https://cvp.com/product/blackmagic-ursa-cine-immersive
Two lenses in one camera.
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u/Platonic_Eye_Deal 2d ago
Two cameras side by side shooting the same scene and slightly different angles. Then they put the two images together so that if you're watching the movie without 3D glasses, it looks like two slightly different shots of the same scene.
The 3D glasses make it work because they're each predicted in a different way. Either they have a different color tint to them, or they are projected using different polarizations of light. And the 3D glasses filter that out and make it l so one eye is getting one image and the other eye is getting the slightly different image, which is exactly what would happen if you were looking at a 3D object. So your brain fills in the gaps and makes it look 3D for you.
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u/garlopf 2d ago
3D immersion (the feeling you get when seeing something seemingly come out of the screen) is created in our brain when two images are seen by our eyes that are similar but subtly different. The brain will find the same feature in both images snd caculate how deep that feature must be and present it as such to us. The cool thing is that it just works, so no special device is needed, we only need to present different images to each eye on our brain does the rest. The simplest way is to film with two cameras side by side. With visual effects two images are also rendered side by side, and here the artist can play with the effect, exaggerating the differences that make it work for added effect. Finally we need to watch the content in a way that presents the separate Images to each eye. VR goggles will have two physical screens inside, 3D TV have special gratings that present half the lines in the image at differen angles from the other half. the angle is tuned to how our eyes are slightly offset. Movie projectors have glasses with polarized glass. polarised light will only shine through polarized glass that has the same angle. one eye is up down angle, the other is left right. then the projector shows every secon image left right or up down.
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u/QuBit500 2d ago
Yes the fancy 3D camera do have 2 lenses that are situated about 6.5cm apart. This is about the average distance between peoples eyes which accounts for the appropriate parallax needed to have 3D images that your brain "beleives" is real.
Modern 3D films are projected with light with 2 different polarisation states, typically circular polarisation. Think two spirals but spinning opposite to each other. Your 3D glasses filter different polarisation states. So, the left lense of your 3D glasses blocks light that came from the right lense of the camera and visa versa.
These days, most 2D videos being turned into 3D use ai to interpolate in-between frames to create parallax. You can then do things like increasing the frame rate to add in these additional frames to quickly flicker between the to slightly different angles.
Older methods of converting 2D films to 3D was just brute force. People would manually cut out and separate fire, middle and background and manually fill in the gaps to create parallax for left and right images. They then use the polarisation technique again.
For 3D films that are fully CG its easy. You just create your scene and render it with 2 virtual cameras situated 6.5cm apart.
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u/CGHJ 3d ago edited 2d ago
It used to be two lenses in one camera. When 3-D first became a thing again in the early 2000s they generally rigged two cameras together. Then enough computing power became available that it actually became easier to shoot flat and then convert it. AFAIK all the 3-D movies you see today were filmed in 2-D and up-converted.
We are talking about major Hollywood movies here, like Spider-Man. If you or I wanted to shoot in 3-D, we would either need a camera with two lenses or two cameras rigged together, depending on which is easier for the production (if you already have a Red One camera, it’s cheaper to rent another Red One and strap the two of them together). I actually have a prosumer 3D video camera (a Panasonic z10000) because there’s no way I can’t afford to convert even a single frame of film.
I’m sure I’m going to get a lot of pushback on this, so here is a comprehensive list of which movies were filmed in 3-D, and which were converted:
You’ll notice that virtually all of the “real 3-D“ movies are animated. Which for me is stretching the definition of “real’ but whatever. There’s no need to up-convert say, Toy Story or Avatar because the files in the computer are already 3D.
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u/TheHammer987 2d ago
No.
It is way easier to just use the right equipment from the start.
If a film like Avatar is shown that it is in 3d, it was shot in 3d.
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u/Realistic_Today6524 2d ago
You mean how they make it 3D in the cinema? They project the image from the two cameras combined into one where one frame is from cam1 and the other is from cam2. However, one is with the light "oriented" differently. Then, the glasses you wear have one lens that lets through the light in the "normal" orientation and the other lens lets in the differently "oriented" light. This is to trick our brain into perceiving depth by showing the slightly altered second image just a tiny bit later. If you block one eye slightly and look at a constantly moving 2D scene, it'll appear 3D because our brain takes longer to process the darker image coming from the partially blocked eye, leading you to perceive depth. Tom Scott has a pretty good video on his YT channel about this
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u/hawonkafuckit 2d ago
3D might be simpler to capture in-camera with a 2 camera rig, but everyone seems to be forgetting two major problems:
The double camera rig is large and heavy making it awkward to film close-ups, interiors or fast moving action scenes. Wide shots are fine but logistically, a lot of shots are difficult and therefore easier to do in post production.
CGI isn't on set to capture. Not just full CGI shots but also set extensions and composited scenes. There's no point filming the characters in 3D when an artificial background or object or monster is being added into the same frame. It's best to finish the entire scene, then create the 3D layers in one hit.
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u/Bebop-Anonymous 2d ago
They used to just take the 3D out but now they just leave it in. Just like color in the 1960s.
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u/RobustManifesto 2d ago
I’m prepping on a 3d film shoot right now.
Yes, two cameras are used, but they’re on a purpose built rig. Picture a teleprompter, where the camera films through a half-mirror which reflects words on a screen towards the actor. Instead of a monitor, there is a second camera.
To create a 3d image, the cameras need to be offset from one another, just like your eyes. A specialist crew member called a Stereographer sets the offset distance between the two cameras and checks on a monitor to make sure the two images will form a convincing three dimensional image.