Historically, non-diegetic user interfaces have been the most common in the gaming industry. The key defining feature of them is that the components of the UI exist on a completely different plane than the actual 3D game space. Imagine here a heads-up display (HUD) as they are likely the most ubiquitous examples of non-diegetic user interfaces. A health bar, for example, does not exist within the 3D space that the game supposes nor can characters in-game interact with it. It is outside both the game’s narrative and space.
According to our survey, a surprisingly high 29% of games developers are primarily building their apps without a third party engine*. They have either written their own engines, or are building everything from scratch. Large games studios very often build their own engines and tools, or customise open source solutions to suit their own internal processes and workflow.