Horn of Calling

Adds a craftable Horn of Calling to the Workbench. Equip it and left click to sound a blast. Its volume is a slider on the Audio tab of the game's settings menu.

Status: in progress. The horn looks and sounds right, costs 1 Bronze + 1 Deer Hide at a level 1 Workbench, and is heard by other players out to 64 m. What is left is the behaviour: see Not done yet.

Plain BepInEx + Harmony, no extra runtime dependency — install HornOfCalling.dll into BepInEx/plugins/ and nothing else.

The mod adds an item and a recipe, so it needs to be on every client and on the dedicated server.

Building

dotnet build HornOfCalling/HornOfCalling.csproj -c Release

Defaults to the Linux Steam install (~/.local/share/Steam/steamapps/common/Valheim), falling back to the default Windows path. Override it by creating Directory.Build.user.props next to Directory.Build.props (gitignored):

<Project>
  <PropertyGroup>
    <ValheimPath>D:\Games\Valheim</ValheimPath>
  </PropertyGroup>
</Project>

A successful build copies the DLL straight into BepInEx/plugins/. There is no hot reload — restart the game after each build.

The build errors early with a named message if assembly_valheim.dll or BepInEx.dll can't be found, rather than emitting a wall of CS0246.

How it works

Three registration steps, all idempotent, driven from Harmony postfixes in src/Patches.cs:

Step	Where	Why there
Clone the prefab, add to ObjectDB.m_items	ObjectDB.Awake, ObjectDB.CopyOtherDB	ObjectDB is built twice — a stripped main-menu copy, then the real world one
Add the Recipe	any of the three patches	Needs the Workbench, which is a piece and may not exist at the first ObjectDB.Awake
Add to ZNetScene.m_prefabs / m_namedPrefabs	ZNetScene.Awake	Lets the item and its sound effect exist as networked objects

The item is cloned from the vanilla Horn of Celebration (prefab TankardAnniversary), which supplies the horn model, the icon and the hold pose without an AssetBundle.

The clone needs three things undone. Its m_ammoType is "mead" — vanilla, the horn drinks a mead from your inventory when you sound it, and refuses to sound at all without one — so that is cleared. Its inherited weapon stats (knockback, backstab, block, parry) are zeroed so the tooltip is just the flavour text. And its start effects, a mead splash and a burp, are replaced by the blast.

The blast is not played by a patch. The clip — a 16-bit PCM WAV embedded in the assembly, decoded in src/HornSound.cs — is hung off the item's m_startEffect, which the game fires once per attack after the stamina check. That also routes it through the SFX mixer group, so the player's volume slider applies.

The clip is peak-normalised to −0.3 dBFS, and that is the whole of the horn's loudness at 100%: Unity clamps AudioSource.volume at 1, so once the mod asks for full volume the only headroom left is inside the recording.

The volume row in src/VolumeSlider.cs is the vanilla SFX row cloned: the Slider sits on the row GameObject with its caption and percentage as children, so one Instantiate copies the whole thing. It is then retitled, spliced into the tab's navigation chain, and pointed at the config entry.

Settings

Settings → Audio → Horn of Calling, sitting under the three vanilla volume sliders. It moves live while you drag it, saves on OK and is discarded on Back, the same as the sliders above it.

The value is stored in BepInEx/config/com.greg.hornofcalling.cfg:

[Audio]
## How loud the horn blast is, as a fraction of the recorded level. [...]
# Setting type: Single
# Default value: 1
# Acceptable value range: From 0 to 1
BlastVolume = 1

Editing the file, or the F1 ConfigurationManager overlay if you have it, applies without a restart — the settings row is a front end for this entry, not a separate setting.

It multiplies Valheim's own sound-effects volume rather than replacing it, and it is per player: it changes every blast you hear, whoever sounded it, and never what anyone else hears. That is why it is not synced through MushroomSync — see docs/CONTEXT.md.

The horn sounds once as a preview when you stop moving the slider — on releasing the handle, or a third of a second after the last arrow-key or stick nudge — at the level you have just chosen, through the same mixer group as the real blast. Moving it again restarts the preview rather than layering a second copy over it, and closing the menu stops it.

Opened from the main menu the slider still works, but is silent: the blast prefab is built from the world's ObjectDB, so there is nothing to preview until a world is loaded.

Not done yet

From the design note, still open:

• 10 stamina per use — m_attack.m_attackStamina, currently 0.
• The roar emote instead of the inherited emote_drink.
• The viking should appear to hold nothing.
• Reaching other players beyond the audible falloff (64 m). Other players do hear the blast today, out to 64 m — see Range — but the design note asks for 200 m. Since Valheim 1.0.7 the zone grid delivers the blast further than the curve carries it (128 m at the default simulation distance), so part of that gap is now a curve-tuning change rather than networking work; the rest still needs a ZRoutedRpc broadcast.
• Hold left click to sustain the sound, release to stop. It is one-shot per click.

Range

Other players hear the horn. The effect prefab carries a ZNetView, so spawning it creates a ZDO that replicates to nearby peers, whose ZNetScene resolves it by hash and plays it locally — which is why the effect prefab is registered with ZNetScene alongside the item.

Two independent limits apply, and the smaller one wins:

Limit	Value	Set by
Audible falloff	64 m	the custom rolloff curve in src/HornSound.cs
ZDO replication	64 m guaranteed, 128 m at the default setting	the listener's simulation distance

The falloff is a plateau curve, tuned in the Falloff table:

Distance	Volume
0 – 15 m	100%
15 – 25 m	82%
25 – 35 m	64%
35 – 45 m	46%
45 – 64 m	28%

Replication is the listener's own Simulation distance graphics setting, clamped by the server's, not a fixed radius. Its lowest level (0) is the pre-1.0.7 one-ring square and reaches 64 m; the default level 2 reaches 128 m, and the levels above it further still. The falloff curve is tuned to 64 m because that is the floor — the only reach every listener is guaranteed to have.

So raising the audible range past a listener's replication radius does nothing: they never receive the object, and no volume setting reaches them. Raising it within that radius would work, and since 1.0.7 there is room to — see docs/CONTEXT.md for the mechanism and why the constant was left at the floor.

Local setup

BepInEx must be installed into the game folder before the plugin can load. On the native Linux build:

1. Extract BepInExPack_Valheim (5.4.2333) into the Valheim directory, then chmod u+x start_game_bepinex.sh.
2. Steam → Valheim → Properties → Compatibility: uncheck "Force the use of a specific Steam Play compatibility tool". Proton breaks doorstop injection on the native build.
3. Steam → Valheim → Properties → Launch Options: ./start_game_bepinex.sh %command%

BepInEx is up if BepInEx/LogOutput.log appears after a launch. If it never does, run start_game_bepinex.sh from a terminal — the Steam container runtime hides the error.

Testing

New world → F5 → devcommands → spawn HornOfCalling 1 1 p. Then stand at a Workbench and confirm the recipe appears for 1 Bronze + 1 Deer Hide. Equip the horn and left click — the blast is ~4.9 s.

spawn Bronze 1 and spawn DeerHide 1 put the materials in reach for a quick check.

For the volume slider: Esc → Settings → Audio, check the row reads "Horn of Calling" and shows a percentage, drag it, press OK, and confirm BlastVolume in the config file changed. Releasing the handle should sound the horn once at the new level, and dragging again should cut the previous preview off rather than stack on it. Walking the list with the arrow keys or a gamepad should stop on the row and preview a third of a second after you stop nudging — if the row is skipped entirely, the navigation splice is what to look at. Pressing Back after a drag should leave the config untouched and the next blast at the old level.

The prefab name is case-sensitive and is not the display name: spawn "Horn of Calling" will not work.

The log names each registration step as it happens, so a partial failure is visible:

grep -i hornofcalling "$VALHEIM/BepInEx/LogOutput.log"

Unity-side stack traces land in ~/.config/unity3d/IronGate/Valheim/Player.log.

Notes

See docs/CONTEXT.md for the API traps behind the design above.