Character Controllers

• NVidia PhysX Character Controller documentation

  In the past, games did not use a 'real' physics engine like the PhysX SDK. But they still used a character controller to move a player in a level. These games, such as Quake or even Doom, had a dedicated, customized piece of code to implement collision detection and response, which was often the only piece of physics in the whole game. It actually had little physics, but a lot of carefully tweaked values to provide a good feeling while controlling the player. The particular behavior it implemented is often called the 'collide and slide' algorithm, and it has been 'tweaked for more than a decade'. The PhysX CCT module is an implementation of such an algorithm, providing a robust and well-known behavior for character control.

  To summarize, a lot of effort can be spent on tweaking and disabling the physics engine's features simply to emulate what is otherwise a much less complex piece of custom code. It is natural to instead keep using that simple piece of custom code.

• Celeste's Player controller source code and postmortem notes