An Introduction to Computer-Generated Imagery: What Is CGI, and Can You Use It in Your Videos?

Computer-generated imagery has become such a staple of modern-day filmmaking that it’s difficult to know what is real and what’s been created in post-production. That’s definitely a telltale sign of great CGI technology. But with all the different terms floating around (between CGI, VFX and compositing, to name a few), it can be hard to distinguish exactly what effect you’re seeing on the screen. In this article, we’ll define what “CGI” means and then give a short historical overview, from the first movie with CGI all up until the latest examples. Finally, we’ll explore the ways you can incorporate CGI animation into your videos to allow you to use this evolving technology in your content.

What is CGI animation?

First, let’s cover a fundamental question: what is CGI, what does CGI mean, and what does CGI stand for? “CGI” stands for computer-generated imagery. This means that what you see on screen is fundamentally an animation intended to appear life-like or create a different visual representation than live-action filmmaking.

Computer-generated imagery can either be 2-D or 3-D. 2-D involves backgrounds, environments, objects and, typically, images that don’t move. The first movie with CGI used this perspective. After all, they’re not allowed to change perspective since that would add another dimension.

3-D, on the other hand, involves all the objects mentioned but is also unique in having actual figures. The key is a change in perspective and movement, and the images mirror 3-D live-action footage.

The key to both CGI types is the quality of the CGI in live-action movies depends on how well it blends with the live-action elements present in the film. However, in the case of an entirely CGI movie (such as a CGI animation film), the quality is graded by how well the image matches the viewer’s visual sense of the world. CGI that feels seamless, where the viewer can’t tell what is real or imaginary, is the hallmark of great CGI execution.

Basic CGI terms

3-D Modeling

This is the process of mapping a 3-dimensional representation using software to do just that. We’ll cover the available software applications to use below.

De-aging

This is the visual effect of making an actor look younger. This can be achieved via VFX editing or by using computer-generated imagery.

Compositing

A final layering step where you combine actual footage shot with the computer-generated image you’ve created.

Green screen

This is a CGI process where an actor (or group of actors) performs in front of a monochromatic screen that is later composited with computer-generated images. The screen itself is typically green or blue.

Keyframe

The markers in an editing timeline where an editor wants to begin or end the chosen effect. Keyframing is essential to making sure your CGI animation happens at the right moment.

Rotoscoping

This is the process of transferring computer-generated images onto live footage frame-by-frame. Although time-consuming, it can achieve superior and life-like effects.

VFX

Think about what VFX is like a giant umbrella. It covers the entire field of manipulating images outside live-action shooting. While CGI is included under this umbrella, so is traditional animation, special effects, matte painting, motion capture and much more.

The history of computer-generated imagery in films

You might wonder when CGI was invented. The first movie with CGI took place in 1973 with the film Westworld. Gunslinger, the character played by Yul Brynner, was an android turned to life. He walks along, and the audience gets a few moments to see through his vision. Created in 2-D fashion, this snippet was the first examples of CGI on the big screen. 

Later in the 70s and 80s, CGI started to become a staple of the sci-fi genre. Star Wars and Alien incorporated and broke ground on wire models. The famous holographic shot of Princess Leia speaking to Luke Skywalker was pioneering.

CGI continued making big strides into the 90s, especially with animation. Pixar changed the visual landscape with its life-like and 3-D models. Titanic is another box-office blockbuster that revolutionized CGI to match complex sequences on an epic scale.

Today, CGI has become so incorporated into filmmaking that it’s difficult to parse. Marvel films have extensively used CGI in creating images unseen 20 years ago. Epic shows like Game of Thrones have created whole characters (and armies) using CGI technology. Some CGI is so seamless it’s hard to tell which was shot and what was added later in post. For instance, directors can set dress a scene in post-production if they missed something during filmmaking. The next painting you see on a wall in some character’s living room might very well be a computer-generated image.

Below, we’ll go over some significant milestones in CGI technology.

Important Milestones in Computer-Generated Imagery

Tron (1982)

This film was the first of its kind to use extensive CGI throughout the film. Backlit animation was used in conjunction with live-action photography to cue the visual effect of taking place in a video game-like setting (due to the source material).

The Abyss (1989)

This James Cameron sci-fi used new effects to create the underwater monster. To create 75 seconds worth of footage, the post-production team needed 6 months of hard work. It paid off, as the film went on to win the Oscar for Best Visual Effects. 

Terminator 2: Judgment Day (1991)

The highest-budget film ever when produced, this film began the transition to CGI over live-action effects. The iconic scene of T-1000 walking through jail bars wowed audiences and required a team of 35 VFX artists to pull off. It, too, went on to win the Oscar for Best Visual Effects.

Jurassic Park (1993)

This film became one of the most successful CGI movies upon its release using live models up close and CGI animation for larger dinosaurs. The compositing and rendering of the dinosaurs took an enormous amount of time, but CGI was making big strides. This too was an Oscar winner for Best Visual Effects.

Toy Story (1995)

The first entirely computer-generated animated film, this film was burned into the cultural consciousness by having a story with heart and mesmerizing visuals. 400 computer models were used to create the characters, and animated design was later integrated to develop the varied features and movements of the characters. 

Avatar (2009)

James Cameron continued revolutionizing the form by creating a dreamscape in this CGI frenzy. Using a motion-capture stage allowed them to replicate the exact movements of actors and render them as the movements of the alien characters in the film. This film won both the Oscar and went on to be the highest-grossing film at the time.

Can you create CGI on your own?

Luckily in the age of digital filmmaking, creating your very own computer-generated images has never been easier. Adobe After Effects is a staple in the industry, and there are loads of resources to catch you up on how to use it. Alternatives to After Effects include Nuke, Hitfilm and Moovly. If you’re tight on a budget, Natron and Blender are free options. Whichever you choose, app developers are keen that CGI is only going to increase.

The future of CGI

CGI is only increasing in relevance, affordability and innovation. To ignore it would be to avoid the possibilities it affords filmmakers today. But that doesn’t mean bad CGI movies don’t exist. While not replacing the need for good storytelling, well-executed CGI has the potential to bolster stories in ways that directors of yesteryear only dreamed of. Having a good base of skills, accessible software and a clear vision are essential to utilizing CGI to its full potential. May you go forward and create the next great example of what CGI cinema can do.