Jumping

Jumping is meant here as adding an upwards impulse to the avatar by a user activity.

This can be achieved for a number of Source ports which implement jumping by using an input device key which can be bound to a dedicated jumping feature.

The original Doom engine, including Doom II, does not offer such a jumping feature. Therefore it was quite simple to keep the player from certain areas already by raising a sector by more than 24 height units, so the player is not able anymore to simply step up onto the higher sector while simply walking or running against its edge. A valuable goal (e.g. a power-up, key, or switch) visible behind a "ridiculously low wall" you just can't step over might be a hint of a secret area with a hidden access.

Usually there are other ways around such an obstacle designed into a map if a valuable goal is placed behind an obstacle you can't step on, e.g. a lift (raising the player over, or lowering the obstacle itself) or stairway, or even the requirement to run over a ledge. Using a jumping feature of a Source port may therefore be considered a Cheat. Doom 64 allows access to its jumping feature after finishing a secret level (MAP32: Hectic (Doom 64) / MAP38: Hectic (Doom 64 TC) in a quite challenging way that requires collecting all three keys.

But an additional engine feature is not the only way to add some upwards velocity to the avatar:


 * The player avatar, in contrast to most non-flying monsters, is able to step up even narrow stairs. This has been used in designing pseudo-ladders to implement a climbing-like behaviour for games which don't support special climbable walls. Running up stairs allows the player avatar to continue its movement in a ballistic curve beyond the top of the stairway, in a certain range (this effect is rather limited).
 * Especially some Deathmatch maps are designed to have areas you could use as ambush if you were able to jump up, which is in fact possible with a certain risk (preferably after collecting a higher amount of armor or powerups like Supercharge, Megasphere, or even Invulnerability) using a Rocket fired close to the own position and getting lifted by its splash damage, the so-called Rocket jumping. In games and source ports which support key jumping as well as looking downwards, optimal timing between jumping and firing a rocket below the avatar may raise it more than its own height.
 * Another risky way due to the received damage: Getting "successfully" attacked by an Arch-vile also raises the player avatar briefly; this is referred to as Arch-vile jump.