parameters.xml

libraries/parameters.xml is the per-class tuning + behaviour-tweaks file — the “constants of the universe”. It defines NPC role tags (which role plays which animation, what tag identifies a missionactor, etc.), ship/station defaults, friendly-fire tolerance per ship class, and many other engine-side knobs.

Vanilla parameters.xml is 2597 lines — second-largest config file after god.xml. Modders touching combat balance or NPC placement diff here.

File structure

<?xml version="1.0" encoding="utf-8"?>
<parameters xmlns:xsi="..."
    xsi:noNamespaceSchemaLocation="parameters.xsd">

  <playerflight>
    <!-- player-flight tuning -->
  </playerflight>

  <classes>
    <class id="ship">
      <!-- class-specific defaults -->
    </class>
    <class id="station">
      <!-- ... -->
    </class>
  </classes>

  <slots>
    <!-- NPC placement slot definitions -->
    <slot tag="npc_missionactor">
      <macros>
        <macro name="character_x_missionactor_macro"/>
      </macros>
    </slot>
  </slots>

</parameters>

Most-modded sections

<playerflight> — player ship physics

Key tag	Tunes
<turnratecap>	Max turn rate
<accelerationcap>	Max acceleration
<boostpenalty>	Boost shield-recharge penalty

<classes> — per-class defaults

Friendly-fire response, alert-level transitions, hull regen per ship class are defined here.

<slots> — NPC role-to-macro mapping

Maps NPC role tags (e.g. npc_missionactor, npc_aipilot) to character macros. Vanilla <slot tag="npc_missionactor"> defines what missionactor NPCs look like.

This is also where the two-layer entity icon distinction documented elsewhere applies: the character-head floater is set_entity_overrides icon=, but the ship-level marker is per-role here (e.g. missionactor → npc_missionactor).

Common patterns

”Soften friendly-fire response per ship class”

<replace
    sel="//classes/class[@id='ship_m']/friendlyfire/@reactiondelay">
    2.0
</replace>

<replace
    sel="//classes/class[@id='ship_m']/friendlyfire/@reactiondecay">
    2.0
</replace>

Pattern from mlog_friendly_fire_tweaks mod. Doubles delay and decay so NPCs don’t immediately turn hostile on accidental hits.

”Add a custom NPC slot”

<add sel="//slots">
    <slot tag="mlog_my_npc_type">
        <macros>
            <macro name="character_mlog_x_macro"/>
        </macros>
    </slot>
</add>

Adds a new NPC tag the mod can reference from MD.

”Override player-ship turn rate”

<replace sel="//playerflight/turnratecap">
    <turnratecap>5.0</turnratecap>
</replace>

For “faster turn for player ship” mod (rarely needed; usually balance-relevant).

Common gotchas

• ⚠ reactiondelay and reactiondecay are friendly-fire tunables. Default values trigger combat too aggressively on accidental hits. mlog_friendly_fire_tweaks doubled both for player-friendly response. (Memory: x4_mod_defaults_xml_ff_softening.)
• ⚠ NPC ship-marker icon is global per-role. Setting set_entity_overrides icon= on a specific NPC only changes the head floater. The ship marker comes from parameters.xml’s slot definition and is shared across all NPCs of that role.
• ⚠ <slot tag=> references engine-side tag definitions. Adding a new tag without engine awareness leaves the entries inert. Most NPC-content mods reuse existing tags.
• ⚠ Friendly-fire tuning is X4-version-specific. Vanilla balance evolves; mods tuning these need to retest each version.
• ⚠ Removing default macros from a <slot> can break NPC spawning. Engine needs at least one macro per slot. Test thoroughly after macro removals.
• ⚠ NPC_Placement_Manager assertions reference parameters.xml. If your MD spawns NPCs and they’re invisible, check that the role tag has a <slot> entry. (Memory: x4_md_npc_placement_manager_requires_slottags.)

Architectural context

• Loaded at game start. Like god.xml, parameters are baked into the running session.
• Mod compatibility: Different mods often touch the same <class> entries. Use precise <replace sel="..."> selectors to avoid stepping on each other.
• Balance mods diff parameters.xml heavily. Friendly-fire mods, combat-feel mods, and player-physics mods all live here.

Related

• Friendly-fire softening — mlog_friendly_fire_tweaks mod.
• NPC — <slot> entries map to NPC roles.
• Entity role — what <slot tag=> references.
• Ship — <class id="ship_*"> tunes ship-class behaviour.

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Pattern — engine tunables file

parameters.xml is the engine-tunables catalog — every number that drives combat / movement / NPC behaviour. Touching it lets you adjust balance without writing MD. But the file is huge and undocumented — always read surrounding context before modifying.