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.
When jumping is not possible, the maximum elevation that the player can step up is 24 map units, therefore allowing to create "ridiculously low walls" that must be lowered or otherwise worked around before the player can reach what lies in plain sight behind, for example a power-up, key, or switch. Therefore, when using a source port that allows jumping in Doom or Heretic, it can be considered a cheat that breaks the normal flow of the map; unless playing maps designed with jumping in mind. Because of this, some source ports allow to disable jumping on a per-map basis, with a keyword in MAPINFO. Doom 64 allows access to its jumping feature after completing a secret level (Hectic) "the hard way".
More limited methods of jumping include:
- 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 behavior 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).
- If looking up and down is allowed by the engine, firing a rocket at the ground and running over it to be lifted by the blast radius allows to perform the so-called rocket jumping. This is possible in vanilla Heretic (with the Phoenix Rod) and in all multiplayer-oriented source ports. Deathmatch maps are often designed with areas only available through rocket jumping.
- 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.