What Is Real-Time Rendering?

Alex Newth

Real-time rendering is a graphics rendering technique — almost exclusive to video games — that helps load graphics. With real-time rendering, frames are loaded instantaneously to create images that simulate actual movement; this also allows video game makers to create interactive worlds. For the rendering to be considered real-time, it must be 15 frames per second (FPS) or faster. The main piece of hardware taxed is the video card, and some older video cards may be unable to keep up with such rendering. In contrast to real-time rendering is pre-rendering, which is sometimes used in video games.

Graphics cards load and process real-time rendering graphics.
Graphics cards load and process real-time rendering graphics.

When someone plays a three-dimensional (3D) game, it should appear to the player that his or her character is running through an environment or performing some action fluidly. In reality, there is nothing fluid about the movements; the video game is just loading images so quickly that it appears fluid, like in animation. Aside from creating movements that are more realistic, this has another advantage: making games interactive. Pre-rendered games, which were made during the early days of video games, were only interactive to a point; some objects could be moved, but the video game’s world as a whole was static. Games that use real-time rendering can have very complex interactions.

Real time applications allow for an instantaneous flow of information.
Real time applications allow for an instantaneous flow of information.

Officially, real-time rendering speed must be 15 FPS or faster. If the graphics cannot load this quickly, then the user will notice obvious loading problems and the game will often lag. Aside from lagging, another problem that a player might notice is that certain images in the game, such as a character’s outfit or background elements, will load very slowly.

To play videos games with real-time rendering, the computer must have a powerful video card, because this is the main hardware taxed during rendering. The video card is responsible for loading and generating all the graphics in a computer, and it must work very hard to ensure the rendering loads quickly. A computer with a weak video card may be unable to generate the images properly, or the rendering may slow down to below real-time speeds.

The opposite of real-time rendering is pre-rendering; this means the video game’s environment is already rendered and placed in the game’s memory. While this technique was mostly used with older games, pre-rendering can be used to make movie segments in a game. While pre-rendering does not use the video card as much as real-time rendering does, the game itself requires more memory, which makes it difficult to create extensive video games that computers can efficiently play.

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