What Is CGI?

What does CGI mean?

CGI means computer generated imagery. A camera records light that was already in the world. CGI works the other way round: you describe objects, materials, light and a camera inside software, and the computer calculates the picture.

That one definition covers very different jobs. A still render of a sneaker that is not manufactured yet is CGI. So is a dinosaur, a digital double of an actor, a cloth simulation and a full animated feature. What they share is that the image never existed in front of a lens. If you want the moving subset explained in more detail, see what computer animation is.

How is a CGI shot made?

In a fixed order, because each stage bakes in the decisions before it.

1. Previz. A rough animatic fixes camera, timing and staging.
2. Modelling. Geometry is built or cleaned up from CAD.
3. Look development. Materials and lighting are tested on stills. This is where realism is actually won.
4. Animation. Movement, weight and camera.
5. Simulation. Cloth, fluids, particles or destruction are computed by physics.
6. Rendering. The machine calculates the final frames.
7. Compositing and grade. Layers are merged with footage or graphics, colour is set.

Feedback is cheap at the start, expensive in the middle and cheap again in compositing. Most troubled projects are projects where notes about the middle arrived at the end. The same logic drives the price, which is broken down in what a CGI commercial costs.

What is the difference between CGI, VFX and animation?

They overlap, and people mix them up. This is the practical split.

Term	What it describes	Example
CGI	The method: images made by computer	A product render, a digital character
Animation	Movement over time	A shoe bouncing, a camera flying through a scene
VFX	The purpose: changing or adding to a shot	Adding smoke or a creature to filmed footage
Compositing	Merging layers into one image	CG hands over a graded background

A single film often uses all four. I work mostly where CGI, animation and simulation meet, which is Houdini FX and CGI commercials.

What are the three jobs CGI does in advertising?

Almost every CGI ad does one of these. This is the framework I use when a client asks whether a brief needs CGI at all.

1. Invent. The thing on screen does not exist, or does not exist yet. A product still in development, an impossible scale, a surreal idea.
2. Replace. A shot that could be filmed but would cost more, take longer or be unsafe. The product stays real in the viewer's mind, the camera work is not.
3. Extend. CG elements are added to real footage, so a filmed scene gets objects, effects or characters that were never there.

Which of the three a brief needs decides almost everything about scope. The decision against a shoot is covered in CGI vs live action product commercials.

What does CGI look like in real campaigns?

Here is what was real and what was computer generated in five projects I produced. This is the part generic explainers cannot give you.

Project	Job	What is CGI	What is not
Trainline Tap That App (via Wieden+Kennedy Amsterdam, 2025)	Invent	The hyperreal hands: modelling, sculpting, skin and nail look development, animation to the beat, lighting, rendering and compositing	Sound and final edit, handled by the agency's partners
adidas ZK 2K Boost (2020)	Invent	Three animated product videos with physics driven motion	Product design and brief came from the campaign
PUMA Be the Spark (2020)	Invent	Modelling, layout, dynamics and timing of a hollow head filled with footballs	Final compositing, done by Nuderobot
Samsung Galaxy Z Flip 7 (2025)	Extend	3D animation placed into real footage with camera tracking and matched lighting	The filmed environment
BASF Design Fabrics (2023)	Invent	Stylized material animations with look development and composition	Original music by David Marquardt

Notice the split: the CG is my part in every row, and what sits around it, sound, edit, final comp or live footage, is what changes. In the Samsung row the quality test is whether you can see the seam. The Trainline hands also ran large as digital out-of-home in UK stations, which is why hyperreal detail mattered: at that size anything nearly right looks wrong.

Why do people only notice bad CGI?

Because good CGI is invisible. Viewers register the failures: weightless motion, lighting that does not match the plate, surfaces that are too clean. When none of those show up, the shot reads as photographed, and nobody files it under CGI.

This is why photorealism is not the quality bar. The bar is how real it needs to look for the viewer to accept it. Stylized CGI such as the BASF fabrics is just as much CGI and much cheaper to get right. The gap between how real it should look and how real it needs to look is often the largest cost driver in a project.

When was CGI invented, and how did it develop?

No single person invented it. Computer graphics appeared in film in the 1970s, for example in Westworld in 1973. Toy Story in 1995 was the first feature made fully with computer animation. Since then the change that matters for advertising is not the look but the workflow: a scene built once now produces a wide cut, a vertical cut, stills and variants, instead of each needing a new shoot.

What does it take to commission CGI?

Four things, and they fit in an email: the goal and audience, visual reference, product data or CAD if there is a product, and every delivery format with the date it has to be live. The format list is the one people forget and the one that costs most later.

If you already know you need a person rather than a studio, hiring a freelance 3D artist explains what I need from you to start. For product films specifically, see 3D product animation.

Got a brief? Send it in a few lines and you will get a straight answer, including when the answer is that a shoot is the better choice.

Written by Marco Mori, 3D artist and creative director in Lindau at Lake Constance, Germany, working with brands and agencies worldwide.