The history
From a 1968 paper that fired imaginary rays at a drawing to film studios path tracing every frame and games doing it 60 times a second.
A computer picture is made by working out what colour every pixel should be. In the 1960s and 70s, researchers learned to hide the surfaces you cannot see, to shade curved shapes smoothly and to add shiny highlights. Then they started following rays of light as they bounce around a scene, which looks real but costs a huge amount of computing. For decades films needed rooms full of computers, called render farms, to finish one frame in hours. Today special chips and AI clean-up let games and film sets trace light in real time.
1968
Ray casting to shade a computer picture and find shadows (widely considered)
Arthur Appel, IBM, USA
1979–80
Recursive ray tracing (reflections and refraction)
Turner Whitted, Bell Labs, USA
1995
Entirely computer-animated feature film
Toy Story, Pixar, USA
2001
Oscar statuette for software (reported)
RenderMan: Catmull, Carpenter, Cook, USA
2006
Feature film rendered with a production path tracer (widely cited)
Monster House, Arnold at Sony Pictures Imageworks, USA and Spain
2016
Pixar feature rendered fully with path tracing
Finding Dory, Pixar, USA
2018
Consumer graphics chips with ray-tracing cores
Nvidia Turing (GeForce RTX), USA
1965 – 1981
Researchers, many of them at the University of Utah, invent the basic tricks: casting a ray per pixel, the z-buffer, and smooth, shiny shading.
1968
Appel described sending an imaginary ray from the eye through each point of the picture to find which surface it hits first. He then sent a second ray towards the light to check whether that spot sat in shadow. It is widely considered the first published work on ray casting for computer pictures.
Why it mattered. One ray per pixel is still the heart of every ray tracer today.
1971
Curved objects in a computer are built from many flat pieces, so early pictures looked like cut gems. Gouraud, a French student at Utah, worked out the brightness at the corners of each piece and blended it smoothly across. He published the method in his thesis and in a 1971 journal paper.
Why it mattered. Blending across flat pieces made curved shapes look curved, cheaply enough for early hardware.
1974
The z-buffer stores how far away the nearest surface is at every pixel. When a new surface is drawn, it only wins the pixel if it is closer. The idea is most often credited to Ed Catmull's 1974 thesis, but Wolfgang Straßer described it in his own thesis a few months earlier.
Why it mattered. It is how almost every graphics chip decides what is in front, even today.
1975
June 1975 (thesis 1973)
Phong, born in Hanoi, blended the direction each surface faces across every pixel, not just the brightness. He added a simple recipe for the bright spot you see on a shiny ball. His thesis came in 1973 and his famous paper in 1975, the year he died, aged 32.
Why it mattered. The Phong highlight is one of the first material models every graphics student learns.
1975
Newell needed a test object and modelled a Melitta teapot, typing its curved surfaces into the computer. Researchers everywhere copied the data to try out new shading ideas. The real teapot is now at the Computer History Museum in California.
Why it mattered. A shared test object let people compare their rendering methods fairly.
1980
June 1980 (shown 1979)
Whitted let a ray that hits a mirror or glass split into new rays, one reflected and one bent through the glass, and followed each of them in turn. The result was glass balls and mirrors that looked startlingly real. Each picture took the computers of the day a very long time to finish.
Why it mattered. Recursive ray tracing gave reflections, refraction and sharp shadows in one clean method.
1980 – 1990
Scientists describe how light really bounces, from coloured walls in a box to one grand equation, and Pixar writes the rules for film rendering.
1982
9 July 1982
Disney's Tron used about fifteen to twenty minutes of computer animation made by four graphics companies. Memory was so small that artists faded distant objects into black to save detail. Some complex frames reportedly took up to six hours each to render.
Why it mattered. It showed Hollywood that computers could make whole scenes, not just titles.
1984
July 1984
The Cornell team used a method called radiosity, borrowed from heat engineering, to work out how light bounces between dull surfaces. A red wall tints the floor next to it red, and their pictures showed it. They later built a real box with coloured walls so they could check the computer against photographs.
Why it mattered. It proved that light bouncing between surfaces, not just direct light, is what makes a room look real.
1984
July 1984
Instead of one perfect ray, they fired many slightly different rays for each pixel and averaged them. Spreading rays across time, a lens or a light gave motion blur, depth of field and soft shadows. It turned blurry, soft effects from a problem into a sampling job.
Why it mattered. Averaging many random samples is the idea behind every modern path tracer, and behind its noise.
1986
August 1986
Kajiya wrote down a single equation: the light leaving a point is the light it gives off plus all the light arriving from every direction and bouncing back out. He also showed how to estimate it by following random paths of light. A team from Cornell described the same idea at the same conference.
Why it mattered. Path tracing, used in films and games today, is a way of solving Kajiya's rendering equation.
1988
Pixar presented the RenderMan Interface, a common language for describing scenes, cameras and lights to a renderer. It included a shading language so artists could write their own materials. Pixar's renderer was built on the Reyes method, which chopped surfaces into tiny pieces smaller than a pixel.
Why it mattered. Programmable shaders let artists invent any material they could describe.
1989 – 2005
Computer-made water, liquid metal and dinosaurs win Oscars, Toy Story is rendered frame by frame on a farm of workstations, and graphics chips arrive in homes.
1989
9 August 1989
In The Abyss, a snake-like column of sea water explores an underwater base and copies the actors' faces. ILM built it on computers, and the team nicknamed it the water weenie. The film won the Oscar for visual effects.
Why it mattered. Making something clear, shiny and bending light proved computers could render tricky materials for film.
1991
3 July 1991
Terminator 2 featured the T-1000, a villain made of shiny liquid metal that could reshape itself. Its computer-made effects appeared in about 42 or 43 shots, alongside many practical effects. It won the Oscar for visual effects.
Why it mattered. A reflective chrome body had to mirror the real set around it, a hard rendering test.
1993
11 June 1993
Jurassic Park mixed life-size robot dinosaurs with computer-made ones for many of the running and chasing shots. Its computer imagery is widely seen as a turning point for visual effects. It won the Oscar for visual effects.
Why it mattered. It convinced film makers that computer-rendered creatures could look alive.
1995
22 November 1995
Toy Story was the first entirely computer-animated feature film. Its 114,240 frames took about 800,000 machine hours, on a farm of 117 Sun SPARCstation 20 computers running day and night. Pixar could finish less than 30 seconds of film a day.
Why it mattered. It showed that a whole feature could be rendered, if you had enough computers and patience.
1999
11 October 1999
Nvidia's GeForce 256 put the maths for moving and lighting triangles onto the graphics chip itself. Nvidia marketed it as the world's first GPU. It rasterised rather than ray traced, but it made real-time 3D fast and cheap.
Why it mattered. Graphics chips grew into the engines that now ray trace in real time.
2001
March 2001
The Academy gave the three an Oscar statuette for advances in film rendering shown in Pixar's RenderMan. It was reported as the first Oscar statuette for a piece of software. RenderMan had by then been used on films such as The Abyss, Jurassic Park and Titanic.
Why it mattered. Hollywood officially recognised that software could be as important as cameras.
2001
August 2001
Light does not just bounce off skin, milk or marble. It sinks in, scatters and comes out nearby, which makes them glow softly. Jensen, a Danish researcher, and colleagues found a fast way to render this, and three of them won a technical Oscar in 2004.
Why it mattered. Subsurface scattering is why computer faces stopped looking like plastic.
2004 – 2018
Studios stop faking light and start simulating it with path tracing. Frames take longer, farms grow huge, and much of the work moves to studios around the world, India among them.
2006
2006 (Academy honour 2017)
Fajardo, from Spain, wrote a renderer that traced random paths of light, as Kajiya had described. Sony Pictures Imageworks used it, named Arnold, on Monster House (2006) and Cloudy with a Chance of Meatballs (2009). In 2017 the Academy honoured Arnold, crediting it with leading a wide move to fully ray-traced film rendering.
Why it mattered. It proved brute-force path tracing could work for a whole film, and studios soon followed.
2013
21 June 2013
Monsters University is described as Pixar's first film to use global illumination, with light bouncing around scenes lit by hundreds of lamps. Pixar's Sanjay Bakshi said a frame took about 29 hours to render on a farm of 2,000 computers with over 24,000 cores. The whole film reportedly used over 100 million CPU hours.
Why it mattered. Simulating real light made lighting easier for artists but hugely more expensive to compute.
2014
June–July 2014
Prime Focus World, part of Mumbai's Prime Focus, merged with the London studio Double Negative, creating a company of about 4,500 people. Now called DNEG, it runs studios in many Indian cities. It has won Oscars for the visual effects of films including Interstellar, Tenet and both Dune films.
Why it mattered. Big film rendering became a global team effort, with India doing a large share of the work.
2014
November 2014
Disney built a new path tracer called Hyperion for Big Hero 6, with light bouncing many times through the city of San Fransokyo. It could show light shining through the robot Baymax's soft vinyl skin. Disney used a farm of over 2,300 computers in four data centres.
Why it mattered. A second big studio switched to path tracing for a whole animated film.
2016
June 2016
Finding Dory was Pixar's first feature to fully adopt RenderMan's new RIS system, a path tracer, replacing the Reyes method used since Toy Story. It also used a denoiser from Disney Research to clean up grainy frames. Lighters could fill fish tanks with dozens of physical lights.
Why it mattered. The studio that invented much of CGI rendering moved fully to simulating light.
2017 – today
Graphics chips gain ray-tracing hardware, AI removes the noise, and game engines light film sets and path trace games live.
2017
With only a few rays per pixel, a path-traced image looks grainy. Nvidia added an AI denoiser to its OptiX software, trained on tens of thousands of rendered images. The same year, a team from Disney, Pixar and university partners published a neural network that denoises film frames.
Why it mattered. Denoisers let renderers stop early, saving huge amounts of time.
2018
13 August 2018
Nvidia announced its Turing chips with RT cores, parts built just to test rays against triangles. Nvidia claimed up to 10 gigarays a second, and said a GeForce RTX 2080 Ti was roughly nine or ten times faster at ray tracing than the older GTX 1080 Ti. GeForce RTX cards reached gamers in September 2018.
Why it mattered. Ray tracing moved from render farms into ordinary home computers.
2019
November 2019
For The Mandalorian, ILM surrounded actors with a curved LED wall about 6 m tall and 270 degrees around. Unreal Engine rendered the background live and shifted it as the camera moved, so the scenery looked right through the lens. ILM says over half of season one was filmed this way.
Why it mattered. Real-time rendering moved from games onto film sets, replacing many green screens.
2022
April 2022
Unreal Engine 5 was released with Lumen, a system for global illumination and reflections that updates as lights and objects move. It can use ray-tracing hardware or software tricks. Bounced light, once a film-only luxury, became a standard feature of a widely used game engine.
Why it mattered. It put film-style bounced light in the hands of small game and film teams.
2022
March 2022
S. S. Rajamouli's RRR used visual effects from many studios, led by supervisor V. Srinivas Mohan. Makuta VFX, with a branch in Hyderabad, said it made around 740 shots, the most of any studio on the film. Makuta also worked on the Baahubali films.
Why it mattered. Indian blockbusters now use the same rendering methods as Hollywood, often made by Indian artists.
2023
11 April 2023
Cyberpunk 2077 added an Overdrive mode that replaced its separate shadow, reflection and lighting tricks with full path tracing. It needed a powerful graphics card plus AI upscaling to run smoothly. It was released as a technology preview.
Why it mattered. The method films adopted between about 2006 and 2016 started running live in a popular game.
2025
April 2025
The Academy honoured Disney's machine-learning denoiser, used since 2018 on over 100 films and shows including Toy Story 4. It also honoured Intel's Open Image Denoise, a free denoiser first released in 2019 and used in renderers such as Arnold. Cleaning up noise had become as important as tracing the rays.
Why it mattered. AI denoising is now a standard final step in path-traced rendering.
Did you know?
Toy Story has 114,240 frames and took about 800,000 machine hours to render; Pixar could finish less than 30 seconds of film a day.
A frame of Monsters University reportedly took about 29 hours to render. Pixar said the whole film would have taken about 10,000 years on a single processor.
The real Melitta teapot that became the famous Utah teapot sits in the Computer History Museum in California.
Ed Catmull, a pioneer of computer images, has aphantasia: he cannot picture images in his mind.
The Cornell box was built for real, so researchers could check their computer pictures against photographs.
The people
1942 – 1975 · Computer scientist · Vietnam, worked in France and the USA
Born in Hanoi, he gave computer graphics its shiny highlight and died aged 32, the year his famous paper came out.
born 1944 · Computer scientist · France, studied in the USA
His smooth shading made curved shapes built from flat pieces look round.
born 1945 · Computer scientist and Pixar co-founder · USA
Credited with the z-buffer and texture mapping, he co-founded Pixar and shared the 2019 Turing Award with Pat Hanrahan.
born 1934 · Professor of computer graphics · USA
His Cornell lab built the Cornell box and trained many people who later won technical Oscars.
1947 – 2025 · Computer graphics researcher · USA
Co-created distributed ray tracing and RenderMan, and shared the first Oscar statuette for software.
born 1955 · Computer scientist · USA
A key architect of RenderMan who later helped model light under the skin, and shared the 2019 Turing Award with Ed Catmull.
born 1969 · Computer graphics researcher · Denmark, worked in the USA
Invented photon mapping and helped computers render light glowing through skin, winning a technical Oscar in 2004.
active since the late 1990s · Software engineer, creator of Arnold · Spain
His Arnold renderer showed that brute-force path tracing could render whole films.
born 1976 · Visual effects businessman · India
Founder of Prime Focus, which merged with Double Negative to form DNEG, with many studios in India.
Where it happened
Sources
Dates marked “c.” are approximate, and historians sometimes disagree about who was first. If you spot a mistake, tell us.
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