Sprinting/zh

疾跑是一个很重要的机制，它使玩家移动得更快，跳得更远.

触发
疾跑是通过疾跑键或双击前进（仅在地面）触发的.


 * It can also be activated with the help of the backward key. In any case, the activation timer is 7 ticks.
 * If the Forward key isn't held, the player stops sprinting.
 * The player stops sprinting after 30 seconds, unless the Sprint key is held.
 * Sprinting is incompatible with Sneaking (except in 1.14+).


 * Colliding with a wall causes the player to stop sprinting on the next tick.


 * Sprinting in air is delayed by one tick (activates and deactivates one tick late)
 * Sprinting cannot be activated when hungry, using an item, or being affected by Blindness.

Speed
Sprinting is 30% faster than walking, granting a base acceleration of 0.13. The asymptotic speed on ground is ~0.286 m/t.

Additionally, when the player jumps while sprinting, they accelerate by 0.2 towards their facing (regardless of whether the player is strafing)


 * This means the player accelerates quickly when sprint-jumping, making it the best way to build speed.
 * Sprint-jumping sideways is actually slower than forward, and goes off-track. But it does have applications:
 * Useful for Backward Momentum, in cases where a regular sprint-jump would give too much speed.
 * Used in the "Sidestep" technique for jumps that require turning. (example)

Code
The following snippets of code deal with how sprinting is activated.

Here is the simplified sequence of steps performed during a tick:
 * 1) Update sprinting status
 * 2) Calculate velocity and move the player
 * 3) Update  and   (multiplied by 1.3 if sprinting), which affect movement speed.

The reason air sprinting activation is delayed by one tick is because the game fetches  when applying air movement (which is updated after the player has already moved). In contrast, when the player is on ground, the game gets the multiplier directly from, which is updated before moving (applies modifier in method  ). is essentially useless in the case of Player entities.