UnitMotion pushing improvements
The main change is the introduction of a 'pushing pressure' counter on units. This counter increases when units get pushed around, and decreases over time. In essence, units under high pressure move slower & are harder to push around.
The major effect is that units can now get bogged down when very dense groups start colliding. This makes movement more realistic, makes unit movement more 'chokepointy', and generally improves the mathematical soundness of the system (lower values are easier to handle for our 200ms turns).
Other changes:
- The logic to detect units crossing each other's path has been reworked. Units that run towards each other should not more obviously avoid each other.
- New parameters: 'Spread' is a measure of how strong the pushing effect is based on distance. With the current settings, static-pushing is rather 'on/off', whereas moving-pushing is more gradual (and thus the max influence distance was increased when moving).
- Default values have been tweaked for lower overlap.
- Units only looked at other units within their grid region. This led to overlap near grid-borders. Units now look at neighboring grid elements, which largely removes this issue. While this may be slower, the performance of pushing was largely negligible before, so it is unlikely to become a main cause of lag (and overlap was generally disliked by players).
- Units no longer orient in the direction of pushing, but instead keep facing their target. This can look slightly odd under very heavy pushing forces, but vastly improves behaviour of very slow units such as rams (since they spend much less time turning around). As a side-effect, clean up angle code following rP25953 .
Engine changes:
- Add a debug rendering mode at compile-time to help understand what is happening.
- Make it possible to constexpr initialise fractional fixed numbers by using FromFraction
The 'pressure' change was inspired by alre's suggestion at https://wildfiregames.com/forum/topic/56436-for-a-better-unit-movement/#comment-461987
Refs #6127
Differential Revision: https://code.wildfiregames.com/D4439