What is real-time?

The term “real-time” is used frequently in creative industries, but is rarely clearly explained. The ability to work in a real-time environment is a major draw to Unity for creators across different industries — but what does real-time mean, and why is it valuable for creators? In this tutorial, we’ll define real-time and learn about the problems it solves.

The term real-time describes how quickly an image is rendered (or displayed) on the screen. The goal of real-time software is to render images so quickly that a person can freely interact with the project without any noticeable delay. When a project or application is real-time, the user never thinks about the fact that they’re just watching a series of constantly updating images — instead they focus on the content. For tool sets like Unity, real-time interaction occurs for both the creators as they build their projects, and for the end-users as they use them.

In the past, computers weren’t powerful enough to quickly render visually complex scenes with physically accurate lighting and effects. In fact, a single still image might take several minutes, hours, or even days to render. To get the look they wanted, creators had to wait a long time to see what they had created. Any errors or adjustments added a lot of time to the production timeline. Iterations were very costly, and experimentation was almost unheard of. New ideas that might improve the final product were often ignored for the sake of meeting the deadline.

This type of rendering, called offline rendering, was utilized for non-interactive media such as film, in which there is only one unchangeable set of images in the final product. Offline rendering can’t be used for interactive media such as video games, where the user expects to control what they see and do. Real-time rendering technology grew out of video games to meet the demand for interactivity. Early real-time renderers were able to sacrifice visual quality, animation complexity, and special effects. As computer processors have evolved, real-time rendering has increased in quality, yielding the real-time photorealistic images in today’s games.

Today, Unity has gone beyond approximating the real world, and is now capable of rendering physically correct materials and lights in the editor; it can also accurately represent physics. These days, if a project detours from real-world visual accuracy and interactions, it’s often a design decision rather than a limitation.

The gap between offline quality and real-time rendering is rapidly diminishing. It’s not 1:1 yet, but it will be — far sooner than most expect.

A still from The Heretic, a short film created in Unity using out-of-the-box features. You can watch the full short film here.

Unless a project specifically requires a quality level that can only be achieved with offline rendering, the benefits of switching to real-time are significant. Eliminating the need to wait for renders has changed the ways creators can work — in fact, creators who move their projects from offline rendering to real-time remove weeks or months from the production cycle, and give themselves more time to experiment with new ideas or polish what’s already been designed. With real-time tools such as Unity, creators can spend all of their production time on creating.

Real-time development is beneficial to both the creator and end user. With Unity, creators can create highly realistic physically accurate scenes for both passive and interactive media. In the next tutorial, you’ll learn more about what Unity does and how it came to be.