Why are 3D movies different from ordinary movies? How are 3D movies made?

Basic Principle

Stereoscopic movies use a shooting device with two lenses like the human eye to capture dual-viewpoint images of the scene, and then use two projectors to combine the images from the two viewpoints. The images are projected synchronously, so that the two slightly different images are displayed on the screen. At this time, if you watch it directly with your eyes, the images you see are overlapping and somewhat blurry. To see the three-dimensional image, you must take measures. Make the left eye only see the left image, and the right eye only see the right image. For example, a polarizing film with opposite directions is installed in front of each projector. Its function is equivalent to a polarizer. The light emitted from the projector passes through the polarized film. After the film is filmed, it becomes polarized light, and the left and right frames display the stereoscopic movie effect

The polarization directions of the polarizers in front of the projector are perpendicular to each other, so the polarization directions of the two polarized lights produced are also perpendicular to each other. Two beams of polarized light are projected onto the screen and then reflected to the audience. The direction of the polarized light does not change. The audience uses polarized glasses corresponding to the above-mentioned polarized light to watch. That is, the left eye can only see the picture reflected by the left camera, and the right eye can only see the picture reflected by the left camera. When you see the picture reflected by the right camera, you will see a three-dimensional scene. This is the principle of three-dimensional movies. Complementary colors, switches, cylindrical lenses, slit gratings, etc. are all different ways of viewing three-dimensional screens based on the basic principle of ensuring that the left eye sees the left image and the right eye sees the right image. As technology advances, people will have more ways to view stereoscopic images on screens.

Principle Analysis

People look at the same object with their left and right eyes. The angles seen by the two eyes are different, and the images formed on the retina are not exactly the same. After the brain synthesizes the two images, It can distinguish the front and back, distance and near of objects, thus producing three-dimensional vision. The principle of stereoscopic movies is to use two cameras to shoot simultaneously to imitate the perspective of human eyes. During the projection, two projectors are also used to simultaneously project onto the same screen for viewing by the left and right eyes, thereby producing a three-dimensional effect. When shooting a three-dimensional movie, two cameras need to be mounted on a special pan-tilt with adjustable angles, and the shooting is based on the principle of stereoscopic movies

at an angle that is consistent with the human eye. The synchronization of the two cameras is very important, because even an error of a few tenths of a second will make the left and right eyes feel uncoordinated; therefore, it is necessary to make a plan when filming, so that the synchronization point can be found during editing. When showing a three-dimensional movie, two projectors are placed in a certain way, and the two images are projected point-to-point on the same screen in complete consistency and synchronization. A polarizer must be added in front of the lens of each projector, one is a transverse polarizer and the other is a longitudinal polarizer (or an oblique cross), so that the screen reflects different polarized lights into the audience's eyes. Audiences must also wear polarized glasses when watching movies. The polarization direction of the left and right lenses must match the projector, so that the left and right eyes can filter out images with different polarization directions and only see the corresponding polarized image, that is, the left eye You can only see the screen projected by the left camera, and your right eye can only see the screen projected by the right camera. After these images are integrated by the brain, stereoscopic vision is produced. A movie that produces a three-dimensional effect when projected by taking advantage of the differences in viewing angles and convergence functions of human eyes. Ordinary movies or photos are shot from a single perspective with one lens, and the images are all on the same plane. People can only create a sense of space based on life experience (such as near and far, light and dark). The three-dimensional movie is composed of two pictures with a horizontal viewing angle difference that are shot from different viewing angles similar to human eyes. When shown, the two pictures overlap on the screen to form a double shadow. They are viewed through special glasses or a radiating half cone in front of the screen. With the shaped lens grating, the left eye of the viewer sees the picture taken from the left perspective, and the right eye sees the picture taken from the right perspective. Through the convergence function of the two eyes, a stereoscopic image is synthesized. Some of the images seen by the audience seem to be deep behind the scenes, and some are out of the frame, as if they can be reached out, giving people an immersive and realistic feeling. Stereoscopic movies that use radial semi-conical lens gratings in front of the screen are strictly restricted by the location of the seating area in the auditorium. The audience's head cannot be moved casually, otherwise the three-dimensional effect will be lost, so the audience will feel extremely inconvenienced. In stereoscopic movies viewed with glasses, colored glasses and polarized glasses are widely used. The color glasses method is to overprint two images taken from the left and right perspectives in red and cyan (or green) colors onto the same screen to make a film strip. General projection equipment can be used during the screening, but the audience needs to wear glasses with one piece red and the other cyan (or green). The eye through the red lens can only see the red image, and the eye through the cyan lens can only see the cyan image. The disadvantage of this method is that the color vision of the audience's eyes is unbalanced and easy to fatigue; the advantage is that there is no need to change the projection equipment. This method was commonly used in early three-dimensional films. A black-and-white dome film using this method was exhibited at the Tsukuba International Science and Technology Expo in Japan in 1985, with better results. Stereoscopic films using polarized glasses have been valued by various countries since 1922. Some countries have combined them with large-field films to produce color stereoscopic films of higher quality and better effects. When this kind of movie is shown, the left and right pictures are projected on a metal screen with polarization axes 90° to each other on a metal screen that does not destroy the polarization direction, forming an overlapping double image. When watching, the audience wears polarized light with polarization axes 90° to each other, and Polarized glasses corresponding to the polarized light of the projection screen can separate the two images to achieve a three-dimensional effect. Due to different production and projection techniques, polarized stereoscopic films are divided into dual-camera and single-camera films. A 70mm large-screen color stereoscopic film was exhibited at the Tsukuba Expo in 1985.

Since the 1960s, the three-dimensional movies shot in China are three-dimensional movies that are viewed using polarized light. In the 1970s, the Soviet Union experimented with holographic stereoscopic movies, which required no glasses when watching and had a wide range of image brightness. Since the visual adjustment and convergence of the audience's eyes is natural and will not cause excessive tension and fatigue, the audience can see the position changes just like the real thing by turning their head. It has a greater sense of depth than ordinary movies, just like the real thing. objects like that. This kind of film is still in the experimental stage of research.

Polarization technology

Have you ever seen a stereoscopic movie? Do you know its principle? It is an example of the application of the polarization phenomenon of light. When watching a three-dimensional movie, the audience must wear a pair of special glasses, which are a pair of polarizers with perpendicular transmission directions. In this way, the scene seen on the screen has a three-dimensional sense. If you don't wear these glasses, the image on the screen will be blurred. Why is this? This starts with the human eye looking at objects. Observing objects with two eyes at the same time can not only expand the field of vision, but also judge the distance of objects and create a three-dimensional sense. This is because when a person's two eyes observe an object at the same time, the images formed on the retina are not exactly the same. The left eye sees more of the left side of the object, and the right eye sees more of the right side of the object. These two images After integration by the brain, the distance of objects can be distinguished, resulting in stereoscopic vision. Stereoscopic movies use two lenses to shoot images of the scene from two different directions at the same time, just like the human eye, and make a movie film. During the screening, two sets of films taken by two cameras are simultaneously projected through two projectors, so that the two slightly different images overlap on the screen. At this time, if you watch it directly with your eyes, the picture you see will be blurry. If you want to see a three-dimensional movie, you must install a polarizing film in front of each movie machine, which acts as a polarizer. The light emitted from the two projectors becomes polarized light after passing through the polarizer. The polarization directions of the polarizing plates in front of the left and right projectors are perpendicular to each other, so the polarization directions of the two beams of polarized light generated are also perpendicular to each other. These two beams of polarized light are projected onto the screen and then reflected back to the audience without changing the direction of the polarized light. When the audience uses the above-mentioned polarized glasses to watch, each eye only sees the corresponding polarized light image, that is, the left eye can only see the picture reflected by the left camera, and the right eye can only see the picture reflected by the right camera, so that It will produce a three-dimensional feeling just like watching it directly. This is the principle of stereoscopic cinema. The three-dimensional movies produced in our country in the 1980s were shot and projected using one lens. Two sets of images were alternately printed on a piece of film, which also required a complex optical path device and polarization system. I will not cover them one by one here. Involved.

Edit this section of the three-dimensional film production process

Script discussion

The requirements and main appeals of the three-dimensional film production customers, and the exchange and communication between the producers.

Concept design

The pre-production process of a professional three-dimensional film commonly used in the industry, including the two-dimensional design of animated scenes, characters, props, etc. drawn according to the script, as well as the overall animation style (tone, Rhythm, emotion, clay sculpture---Lord of the Rings, Star Wars, Hulk, etc.) positioning work to provide reference for subsequent three-dimensional production.

Storyboard storyboard

The actual production of storyboards based on text creative scripts, hand-drawn drawings to construct the picture, explain the camera movement, and narrate the plot to provide reference for subsequent three-dimensional production.

Rough model

In three-dimensional software, the modeler makes a rough model of the scene, characters, and props of the story in preparation for the storyboard (Layout).

3D Storyboard (Layout)

Use a 3D rough model to create a Layout (3D Storyboard) based on the script and storyboard. This includes knowledge such as camera position arrangement, basic animation, and lens time customization in the software.

3D character modeling\3D scene\prop model

According to the conceptual design and the comprehensive opinions of customers, producers, directors, etc., accurate production of models in 3D software is the final step All the "actors" in the animated film.

Texture materials

Based on the concept design and the comprehensive opinions of customers, producers, directors, etc., the 3D model is "made up" and the color, texture, texture, etc. are set. An indispensable and important link in the animation production process.

Skeleton Skinning

According to the storyline analysis, some deformation, motion drive and other related settings before animation are performed on the 3D models (mainly characters) that need to be animated to provide animators with Make preparations and provide animation solutions.

Storyboard animation

Referring to the script and storyboard, the animator will create a performance for each shot based on the shots and time of the Layout for the characters or other objects that need to move. For animation, there are manual keyframes and motion capture. Animation adjustment in 3D animation is a similar way of thinking to 2D animation, but 3D animation has great advantages in this work. We know that there are "original painters" and "animators or intermediate painters" in the production of 2D animation. In the world of 3D animation, designers do the work of "original painters". We operate the skeletal system at different key frames. Set animation. All the work of the "animator" is automatically completed by the computer.

Lighting

According to the style positioning of the early concept design, the lighting engineer illuminates the animation scene, describes it in detail, and adjusts the materials carefully to grasp the rendering atmosphere of each shot.

3D special effects

According to the specific story, produced by special effects artists. The actual production and expression methods of several water, smoke, fog, fire and light effects in 3D software (Maya).

Layered rendering/synthesis

After the animation and lighting production are completed, the rendering staff will render each lens file in layers according to the opinions of the post-production compositor, and provide layers and layers for synthesis. aisle. The dubbing and soundtrack are required by the script design. Professional dubbing artists will dub according to the shots, and add appropriate background music and various sound effects according to the plot. The music for the film can be composed or selected. The difference between the two is: if you compose music, the film will have unique music, and the music can be perfectly integrated with the picture, but it will be more expensive; if you choose music, it will be more economical in terms of cost, but other films may also Use this music. The narration and dialogue were completed at this time. After the narration and dialogue are completed, and the music is completed, the sound effects editor will add various sound effects to the film. At this point, the sound elements of a three-dimensional film are all prepared. The last process is to combine all the above. The individual volumes of the elements are adjusted to the appropriate position and combined together. This is the last step in 3D film production. After this step is completed, the 3D film is completed.

Post-editing

The rendered images of each layer are synthesized into a complete film by post-production personnel, and edited into different versions according to the opinions of the client, producer and director to meet different needs. .

Edit how to watch this paragraph

1. Space separation method

It is commonly used in movie theaters. Nowadays, many theaters have 3D stereoscopic screening rooms. During the screening, two projectors are used to play the movies shot by two cameras. Two sets of differentiated images will appear on the screen simultaneously. It is generally useful to use polarized glasses to watch. Spectral glasses.

Flicker-free 3D technology

Flicker-free 3D TV method is the closest to our actual experience of three-dimensionality and the most natural way. Just like enjoying vivid 3D images in a movie theater, you can watch two images at the same time by attaching a special film that separates the left image and the right image to the surface of the 3D TV and glasses. The left and right images are separated through the TV and sent to the glasses at the same time. Through the filtering of the glasses, the separated left and right images are sent to each eye. The brain then synthesizes the two images to make people experience a 3D stereoscopic feeling. Features of Flicker-free 3D: Regarding viewing angles, Flicker-free 3D is not a problem at all when viewed within the recommended audio-visual distance. For example, except for watching TV while standing, sitting or using very abnormal postures within one meter, there is no problem when watching the 3D TV within the audio-visual recommended distance. The only disadvantage is that when playing 1080p, it is only 540p, which means the image quality is halved, resulting in insignificant effects. Advantages of the non-flicker type: First of all, there is no flicker, and it can reflect 3D images that are very comfortable for the eyes. Flicker-free 3D has no electric drive, making the glasses comfortable to wear and with no flickering sensation at all. Therefore, you can enjoy 3D images that are very comfortable for your eyes. Looking at the data actually measuring the degree of flicker, we can see that the data is almost zero, and there will be no dizziness. You can enjoy 3D images with lightweight and comfortable glasses. Flicker-free 3D glasses are lightweight and reasonably priced, and can also be used with jacket glasses to make them comfortable for people who wear glasses. Reflects 3D images without overlapping images. The overlapping phenomenon occurs when the right image enters the left eye or the left image enters the right eye. The special film used in flicker-free 3D separates the left and right images to reflect the 3D image, so there will be no overlapping of images and you can enjoy the three-dimensional image as if you are seeing a living real object. By actually measuring the data of screen overlap, we can know that the overlap data of non-flicker 3D is at a level that humans cannot perceive.

2. Complementary color technology

It is another 3D stereoscopic imaging technology. It is also relatively mature now. There are many modes such as red and blue, red and green, but the principles used are the same. Same. The color separation method prints images taken from two different viewing angles in two different colors on the same frame. In this way, when the video is shown, you can only see blurry ghost images when viewed with the naked eye. However, you can see the three-dimensional effect through the corresponding red and blue stereoscopic glasses. Taking red and blue glasses as an example, you can only see red under the red lenses. Blue lenses can only see blue images, and the different images seen by the two eyes overlap in the brain to create a 3D effect.

3. Time division method

The time division method requires the cooperation of the monitor and 3D switch glasses to achieve the 3D stereoscopic effect. The structure of the three-dimensional glasses used in the time division method is somewhat complicated, and of course the cost is higher. Both lenses are electronically controlled and can switch states according to the output of the display. The lens's light-transmitting and non-light-transmitting switching allows the human eye to only see the corresponding picture (in the light-transmitting state), and the two eyes see different images. The picture can achieve the effect of three-dimensional imaging.

Advantages: The most widely used and relatively abundant resources Disadvantages: 1. After wearing glasses, the brightness decreases greatly; 2. The opening and closing of the shutter of 3D glasses is not completely synchronized with the left and right images under the action of fluorescent lamps, and crosstalk and ghosting will occur. ; 3. The price of shutter-type 3D glasses is basically around 1,000 yuan, which is relatively expensive and requires the installation of batteries or charging.

4. Raster type

In order to receive television stereoscopic programs in preparation for the 2008 Beijing Olympics, our country has manufactured its own raster-type three-dimensional TV sets. However, the raster type also has shortcomings, that is, clarity and Other stereoscopic models are worse than others, and only have slightly higher definition on very large TVs. But as a result, the price will go up. To overcome this shortcoming, we need technological progress.

5. Platts Stereo

This is a way of viewing three-dimensional images discovered by a veteran after World War I (it is also called True Stereoscopic in China). This three-dimensional TV technology It is compatible with the original TV equipment of various standards. The principle is to move the camera to the left or right at a constant speed when shooting stereoscopic programs, mainly to achieve the effect of motion stereoscopic. When watching the program, the audience wears a pair of special glasses that correspond to moving left or right. One of the lenses of these glasses is transparent and the other is translucent. The cost is low. If you don't wear glasses, there is no difference from watching ordinary TV. The reason why this technology is facing elimination is that the films taken by moving left and right are easily confused with the glasses worn for viewing, resulting in an insignificant three-dimensional effect, and its good compatibility has been over-hyped. Since the 1980s, it has been around the world Dozens of countries experienced ups and downs.

6. Viewing mirror:

In the past, it was specially used to view the picture pairs taken by the stereo camera. The picture pairs were generally presented left and right. Now this kind of screen viewing mirror can also watch left and right stereoscopic movies. Disadvantages: Only half the size of the screen when viewing images or movies; Advantages: Very clear.

7. Holographic type:

This type cannot be promoted at present. It looks three-dimensional from all angles, no need for stereoscopic glasses. The price is surprisingly expensive and it is only displayed in the Science and Technology Museum.

The 3D movies we see in cinemas now are generally post-production. It is said that 3D movies do not have many effects. When they are played in cinemas, two projectors are used to play the effects. It’s not obvious. The 3D effect of Kung Fu Panda is very good, but after watching it for a long time, the glasses will not be so obvious as your glasses get used to it or you will get tired. You need to take off your 3D glasses and take a rest before you can continue watching. If you want to watch 3D movies, go to some more professional places to watch 3D short films.