Movement

From DDraceNetwork
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Movement is one of the core aspects of Teeworlds and DDrace.

Basics

Gravity

Every tick the acceleration of 0.5 is added to the y velocity (downwards) due to gravity.

Jumping

Ground jumping sets a tee's y velocity to -13.2, scaled by a value.

Air jumping (double-jump) sets a tee's y velocity to -12.0, scaled by a value.

Jumping will set the y velocity, cancelling out any previous upwards or downwards velocity. This is very useful in scenarios where you need to halt large vertical impulses.

TODO: Find the bps value or scaled coefficient for these values (same with the horizontal movement, these values are not in bps)

Horizontal Movement:

  • Pressing nothing:
    • Ground: Every tick velocity.x = velocity.x * 0.5
    • Air: Every tick velocity.x = velocity.x * 0.95
  • Pressing key in opposite direction:
    • Ground: Every tick the horizontal velocity decreases by 2 until 10 in the opposite direction is reached
    • Air: Every tick the horizontal velocity decreases by 1.5 until 5 in the opposite direction is reached
  • Horizontal speed up by pressing a or d:
    • Ground: Every tick the horizontal velocity increases by 2 until 10 is reached
    • Air: Every tick the horizontal velocity increases by 1.5 until 5 is reached\


Friction is ignored when holding down a key. So, at high velocities, pressing nothing will slow a tee down faster than moving in the opposite direction, as the friction will have an exponential slowdown compared to the a/d linear slowdown.

Advanced

Max Speed

Max speed: 6000 Sub-tiles/Tick (+speedup in one tick, e.g. gravity, jetpack, explosion).

src/game/gamecore.cpp (before calculating new position from velocity):

if(length(m_Vel) > 6000)
    m_Vel = normalize(m_Vel) * 6000;

This is the bottleneck in vertical movement. In horizontal movement a “ramp”-Value is multiplied to the horizontal speed. Causing the tee to slow down and stop when getting too fast. This is most commonly observed in speed ups.

The speed is rounded down to a precision of 1/256 every tick. This is causing the tee to stop moving horizontal when having too much speed.

TODO: * convert sub-tiles/tick into tiles/sec * find max vel und real max vel (from where would a constant function fit) * find speed, where the tee stops moving * write about ramp speed, and add diagram

Corner Skimming

A tee is considered on the ground only due to its position and distance to the ground - it does not require the tee to have downwards velocity. So, it is possible for a tee to be "grounded" while traveling upwards, as long as the tee skims the corner of a tile.

Corner skimming:

  • allows a tee to refresh its double-jump (useful when skipping maps such as Impetuous).
  • can apply ground acceleration and max speed to a tee for a short amount of time (assuming the tee's horizontal midair speed is less than the maximum ground speed prior to corner skimming)


Corner skimming is not often intentionally used in map parts (except for maps such as Short and Precise 7), but can be used in short speedruns as small optimizations.

TODO: add gif

Elevated Jump

A ground jump can be performed even if the tee is a few subunits above the ground.