A game engine is ready-made software for building video games. It draws a game's graphics, runs its physics, plays its sound and reads the player's controls, so that a studio does not have to build all of these itself. Unreal Engine and Unity are two of the best known. The same engines are now also used to draw backdrops for films, dashboards in cars and other moving pictures on screens.
An engine has two parts. The runtime is the code that runs inside the finished game, on the player's phone, PC or console. The editor is the tool that the studio's developers and artists work in. In the editor, they place characters, buildings and lights in each level. They write the game's rules in a programming language, or by joining visual blocks.
The runtime repeats one cycle many times every second. First, it reads the player's touch or button press. Next, it moves every object, using the physics system, which works out how objects fall, collide and bounce. Then it draws the whole scene as one picture, called a frame. A game that runs at 60 frames per second has about 16.7 milliseconds to do all of this, for every frame.
Imagine a three-person studio in Jaipur building an auto-rickshaw racing game for phones. Without an engine, the team would spend months just drawing 3D roads and making the rickshaws tip over on sharp turns. With an engine, the physics, the lighting and the sound already work. So the team spends its time on the tracks, the vehicles and the rules of the race. When the game is ready, the engine builds one version for Android phones and another for iPhones, from the same project.
How do engine makers earn? Some engines take a share of a game's revenue above a threshold. For example, one well-known engine charges 5% of a game's revenue above the first $1 million, which is roughly ₹8.5 crore. Others charge a yearly subscription for each developer. A few engines are free and open source.
Engines are used by console and PC games and by free-to-play mobile games alike. A user-generated games platform gives its players a simple engine of its own. Outside games, film crews use engines on a virtual production stage. There, huge LED screens show a computer-made background that moves as the camera moves. Car makers use engines to draw the instrument cluster behind the steering wheel. Marketers use them for augmented reality marketing.
In India, a studio in Pune is building a large cricket game on Unreal Engine.