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Filmmaking 101: What is CGI in Movies and Animation?

Jakob Straub
Jakob Straub, Content Writer

Computer-generated imagery or CGI for short is a large portion of what we perceive as the 3D computer graphics of video games, movies, and TV shows. CGI can create characters, scenes, backgrounds, special effects, and entire animated films. In a film project, computer-generated images are part of the visual effects or VFX department.

Let’s look at what exactly makes up CGI in movies and animation, how the technology works, how it evolved, and what some famous CGI examples are.

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What is CGI: Defining computer-generated imagery in movies

Computer graphics are more than animation and visual effects for films. Computer-generated imagery can appear in art, print media, video games, simulations, architectural or anatomical models, advertising, news, TV, film, and animation. AI image generators using deep learning such as DALL-E, MidJourney, or Deep Dream can produce artificial images in various styles from a text prompt.

Computer-generated imagery (or CGI for short) uses computer graphics to create art or media in 2d or 3D for print or screen products, film, television, computer games, simulations, or virtual reality experiences. Animation and film can rely on CGI alone, while blockbuster movies often employ a wide range of CGI effects in combination with live action to create composites. CGI can produce flat shapes or complex forms and 3D models with various light sources, reflecting surfaces, particle effects, and realistic physics. The technology uses software to create models and scenes, sometimes with the help of 3D capturing, and computing power to output the final sequence of frames in a process called rendering.

In filmmaking, CGI can deliver two-dimensional graphics, for example, for text, objects, backgrounds, or environments, and three-dimensional objects, characters, landscapes, environments, and complete scenes. Complex and costly CGI creates visual effects and composite images that look realistic or realistic enough to trick viewers, making them suspend their disbelief. However, “bad” rendering creates visual clashes, artificial objects in real environments, and effects which viewers have a hard time accepting. Animated films often create a typical, non-realistic look that might resemble cartoons, but can use intense and elaborate CGI with realistic effects.

Computer animation and CGI: what CGI is not

Computer-generated images can be static, but become computer animation when the continuous imagery comprises frames in sequence, thus creating computer animation. The resulting scenes or movies are dynamic images with no viewer interaction. Virtual reality environments and video games also use CGI but enable the user to interact with the virtual world.

In filmmaking and animation, computer-generated imagery evolved from frame-by-frame animation achieved with hand-drawn illustrations or stop-motion technique and ‘claymation.’ CGI does not refer to these, though today animated movies might use CGI in a blend with other animation techniques.

Outside of the world of movies, CGI also refers to Common Gateway Interface for data exchange between web servers and web applications. Before you hire the wrong CGI specialist for your film project, clarify that you’re talking about computer graphics and not CGI programming.

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How filmmakers use CGI for visual effects

VFX artists had to use props, lighting, models, and other real-life practical effects to create visual and special effects for films. CGI increased the range of possibilities and today, filmmakers use the technology in various ways:

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    Pre-visualization: VFX artists use pre-viz to simulate live-action shots with 3D computer models to show the director and cinematographer a preview of shots. That way, they can test visual approaches and narratives without having to stage them in real life.
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    2D animation: CGI animators can create “flat” characters and environments for animated scenes and movies, for example, for simple visualizations, but also for cartoon-like movies.
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    3D modeling: The VFX department can use CGI to create 3D objects, characters and scenes from scratch, or add them to existing images, like actors in the background.
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    3D Animation: Computer-generated images can deliver an entire world and characters to create a full-length film in a virtual environment.
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    Special effects: CGI can use CGI special effects to change the lighting in a scene, or the appearance of a background, or an actor, including de-aging to make them look younger. VFX can also add CGI effects in the environment, such as rain, storm, or snow, and of course, fire and explosions.

CGI techniques and departments in filmmaking

In modern film production, computer-generated imagery involves not only those in VFX jobs. The various techniques and applications for CGI extend to other roles and parts of the production process.

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    Art department: The work and designs of concept artists and storyboards are part of how the art department translates the script and the director’s vision into visuals which will also form and feed into the style of computer-generated images from the visual effects department.
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    Pre-viz artists: As mentioned above, pre-visualization uses bare 3D models or low-quality renders to show scenes and shots for planning camera placement and other requirements.
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    FX simulation: These artists have a highly technical, yet still creative role. Their work concerns the difficulties of rendering, i.e. the realistic simulation of particles and fluids, to create convincing CGI of water, fire, explosions, textures, hair, and more.
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    Lighting: For composite scenes, the digital elements created by CGI have to match the lighting of the live-action scene. Lighting artists create virtual light sources to mimic the lighting of the environment for a seamless blend. Similarly, the light of effects such as explosions has to affect the live action.
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    Asset department: These artists create models, textures, and shades for virtual assets, which can match real-world objects for visual effects, or create assets which otherwise wouldn’t be possible in the real world.
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    Research and development: Rendering requires time and processing power. The technical department of RnD will try to reduce these by developing or enhancing software, tools, and hardware to assist VFX artists.
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    Motion tracking: Also called matchmove, this technique can capture live-action footage to incorporate it into digital surroundings. Motion tracking can also move a virtual camera to match a real one so virtual assets can blend into live-action footage.
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    Rotoscoping: These VFX artists build a matte or mask for an object so it can be treated differently than the rest of the footage, for example, for color changes.
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    Matte paint: Digital painting technique and computer-generated images can deliver backgrounds and scenes that don’t exist in the real world, or are a replica of existing places which are otherwise unable for filming on location.
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    Compositing: The process of compositing comprises layering the individual elements of a shot, such as live-action footage, mattes, lighting, computer graphics and animation, and effects. The result of compositing is the final, photorealistic shot.

Brief history of technology and CGI in movies and animation

Computer-generated imagery dates back to the 1960s. The first time that CGI appeared in a film was with Alfred Hitchcock's Vertigo in 1958 and the use of patterns for a 2D animation. A Computer Animated Hand by Edwin Catmull and Fred Parke is a 1972 short film that introduced 3D computer graphics, digitizing a hand with 350 triangles and polygons. The first CGI in a feature film was Westworld in 1973 with its "Gunslinger" robot vision in 2D.

What followed were wire-frame models, as seen in Star Wars (1977), Alien (1979), and The Black Hole (1979). Visual effects pioneers such as Industrial Light & Might, founded by George Lucas in 1975, kept pushing the boundaries of VFX and CGI in the 1980s. That decade saw titles like Tron (1982), The Last Starfighter (1984), Young Sherlock Holmes (1985) and The Abyss (1989) make use of CGI technology.

In the 1990s, CGI masters used all their know-how to get the most out of the technology available at the time and released groundbreaking titles such as Terminator 2: Judgment Day (1991), Jurassic Park (1993), Toy Story (1995), and The Matrix (1995).

The new millennium saw CGI speeding up and with new software and hardware, possibilities increased, as Peter Jackson demonstrated with the Lord of the Rings trilogy. Gollum was the first CGI character to interact with real actors. Today, movies such as The Avengers or Guardians of the Galaxy use CGI for thousands of shots or 90 per cent of the movie.

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Examples of CGI in movies

The following compilation of movies that use CGI shows the evolution of the art and the possibilities of ‘new CGI,’ the various techniques filmmakers employ, and the stepping stones in the evolution of CGI movies.

Interstellar (2014)

Christopher Nolan's space travel exploration features a supermassive black hole and a tesseract, where Cooper encounters interlinked timelines to communicate with his daughter in the past. The VFX department used slit-scan photography (similar to 2001: A Space Odyssey) from which they created a digital version of the room to generate the extruded timelines.

Jurassic Park (1993)

Steven Spielberg not only laid the groundwork for a major motion picture franchise with the first Jurassic Park movie, but he also introduced viewers worldwide to realistic computer-generated images of a grand scale. The VFX crew realized many dinosaur shots with realistic movements, texture, and scale only with CGI.

Avatar (2009)

While viewers are still awaiting a sequel, the original Avatar by James Cameron is a CGI tour de force with fantasy creatures and an entire world created from scratch and realized with complex models, composites, and great detail.

The Matrix (1999)

Few movies can claim to have a special effect named after them, but The Matrix achieved that with “bullet time,” in which time slows down while the camera keeps moving at normal speed. The movie helped raise the bar for action movies and their use of computer-generated imagery.

The Irishman (2019)

Martin Scorsese's epic extends over three and a half hours and might not seem like a typical CGI movie (if such a thing exists). It's certainly not the only one making use of de-aging technology, but it's arguably one of the best, making Robert De Niro, Al Pacino, and Joe Pesci look younger naturally.

Titanic (1997)

James Cameron again, and at his best: Titanic is a great example of “good” CGI. The ship was literally too big to re-create entirely as a live-action model, so the film combined footage of the actors with digital backgrounds and models in very convincing composites.

The Lord of the Rings trilogy (2001–2003)

Peter Jackson’s Lord of the Rings trilogy uses a lot of CGI, but the character of Gollum stands out as one of the earliest examples of 3D motion capture. The VFX team recorded actor Andy Serkis three times: with a white suit, in a motion capture studio, and for his voice off camera, to match his facial expressions with a 3D CGI character.

Toy Story (1995)

The first Pixar movie pioneered 3D computer animation in a feature film. Today, 3D computer-animated characters in complex stories are the standard for animated films, and Pixar has proven the concept time and time again.

Terminator 2: Judgment Day (1991)

The T-1000 is mightier and scarier than the original Terminator, and to achieve that vision, James Cameron had to rely entirely on CGI to create the villain made of liquid metal with his unique abilities.

Transformers (2007)

Michael Bay’s movies might not be known for their outstanding plots, but Transformers shows the incredible detail that CGI can bring out: individual frames took up to 38 hours to render because the models comprised ten thousand individual parts. The transformations of the characters look stunning, and yet were only a step in the evolution of CGI, with the number of components in models soon quadrupling.

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