Simulation Modelling

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X3 is a game that simulates a fictional universe comprised of sectors of space connected by gates, the X-universe.

As a concession to limited processor capabilities available to most home users, X3's simulation of the universe's processes are simplified when not in direct view. This leads to two modes of simulation known in the community colloquially as IS and OOS.

IS, either In-System or In-Sector, are things rendered within the same system or sector the player is in. Since the player can interact with them, they must be modeled as physical objects, subject to collisions. Time is evaluated in very fine chunks.

OOS, or Out-Of-Sector, are things that happen outside of the system the player is in. Since the player has no direct contact with these objects they can be simplified to statistical events, thus removing collision checking.

The difference in modelling causes some unexpected behavior in OOS mode, as the objects no longer have to obey physical constraints and as for further computational savings, time is evaluated in larger chunks. Furthermore, OOS events the player is not directly monitoring through the Trading Extension occur in larger time chunks than those that are being directly monitored.



  • Combat is modelled in real-time, accounting for projectiles, collisions, and orientation.
  • Movement takes into account obstacles and potential collisions, and ships must manoeuvre around obstacles.


  • Combat is simplified to a turn-based system considering the full installed weapon power of combatant ships.
  • There is no collision avoidance and it is perfectly legal for two ships to occupy the same position in space.

Combat Example: Out-of-Sector[edit]

Turns run 30 seconds, 5s if monitored via sector map.

50 Jaguars w/ 4 IREs & 2 1MJ shields costing about 70k credits each.
Python w/ lots of guns & 3 2GJ shields costing over 90M credits

4 IREs will cause 560 Hull/5.6 MJ Shield damage/sec, over 30s this is 16.8K/168MJ, for 50 this is 840K/8400MJ, on a 5s time-step this converts to 2.8K/28MJ per ship, and 140K/1400MJ for 50.

A Jaguar has 2MJ in shielding and 800 hull points.
If the Python is armed, it will do enough damage to kill a jaguar, unfortunately, OOS combat tends to not account for things like Area Effect weapons or permit targeting multiple ships like an M2 would ordinarily do against a fighter swarm.

A Python has 6GJ in shields and 400K hull points.

If you watch the fight on the sector map what will probably happen is the Python will kill 5 Jaguars while they pare down the shields and inflict a little hull damage. It will then kill another 4-5 while the survivors destroy the rest of the hull. It will probably fare worse if you don't watch the fight.

Result, Jaguars suffer approximately 20% casualties for complete destruction of the M2. This analysis neglects shield recharge which will tilt the outcome in the Python's favor, but not enough to win.

The results of an In-Sector battle will go completely differently, especially if the Python is armed with Flak weapons. A number of the M5s are quite likely to collide with the M2 and cripple or destroy themselves. The Python's weapons fire will generally miss the small and manoeuvrable M5s. M5 traffic control will reduce the number of attackers that can effectively attack at a single time. Fighter manoeuvres will reduce the time spent firing during each pass. It is most probable that the Jaguars will be completely annihilated without causing significant damage to the Python.