Portal rendering is a technique used in video games to limit the amount of pixels rendered at one time, improving performance by requiring less memory. The game world is divided into sections or portals, with only the visible section being rendered. This technique is commonly used with indoor rooms, but can also be used with outdoor landscapes if the user’s field of view is taken into account. While problems are minimal, unexpected user movement may cause loading issues.
Portal rendering is a computer graphics technique used in video games to limit the amount of pixels rendered at any one time. To achieve this, most games are made up of sections and the user can only see a certain area, such as a room. These sections are usually small and limited, because it’s easier to program, but portal rendering can also be used with outdoor landscapes if the programmer takes into account the user’s field of view. The primary reason for using this rendering technique is to improve performance by requiring less memory. While problems tend to be minimal and mostly affect older games, there may be loading issues if the user moves unexpectedly.
With portal rendering, the programmer will often divide the game world into many portals or sections. When someone is in a certain section, the programmer knows that the other sections will not be displayed and, therefore, will not need to be rendered. This is commonly done by creating rooms, with each room being used as a section.
To make rendering even easier, most sections are bordered by clearly visible walls. If limited space is used, portal rendering becomes easier, because the programmer has to make few assumptions about what the user will be able to see. Some games feature outdoor landscapes with no walls. In this case the programmer must take into account the user’s field of view, so that only the immediately visible landscape is rendered.
The main reason to use portal rendering is that it limits the amount of memory you need out of the box. For example, if the game map is unsliced, the game must render all pixels at the same time. This requires a lot of memory which means that the performance of the game will likely suffer from lag and other issues. The user is usually not close enough to see another section, so this delayed rendering usually doesn’t cause any problems.
While there are usually no problems with portal rendering, it is possible that some pixels may not load correctly if the user does not move as expected. For example, if the programmer assumes the user won’t go to the previous section and they do, the game might take a few seconds to load the section. There may be a wall or small area that appears black for a second, but this rarely affects game performance.
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