Audio

The four events

ESDFAudioEvent:

Event	Emitted when
LightImpact	A valid hit below the profile’s heavy thresholds
HeavyImpact	A hit at or above HeavyImpactMinimumPower or HeavyImpactMinimumImpulse
Break	The object is destroyed
DebrisImpact	A spawned debris piece collides fast enough

Weighted variations

Each event reads an array of FSDFWeightedSound from the profile:

Property	Default	Meaning
Sound	none	Soft USoundBase reference
Weight	1.0	Relative selection weight
MinimumVolume	0.9	Lower bound of the volume multiplier
MaximumVolume	1.0	Upper bound
MinimumPitch	0.95	Lower bound of the pitch multiplier
MaximumPitch	1.05	Upper bound

Empty entries and zero-weight entries are ignored safely — an incomplete array never crashes and never plays silence.

SoundBase is the accepted type, so Sound Waves, Sound Cues and MetaSound sources all work. The profile can also carry an optional SoundAttenuation and SoundConcurrency asset applied to built-in playback.

Shipped break cues

The runtime profile templates generated by the authoring presets come with a break sound already assigned, from the plugin’s own demo audio:

Preset family	Break cue
Wood, Wooden Crate, Wooden Furniture, Wooden Coffin	SC_SDF_WoodenCrate_Break
Wooden Barrel (Semantic)	SC_SDF_WoodenBarrel_Break
Ceramic	SC_SDF_CeramicImpact
Stone	SC_SDF_StoneImpact
Glass, Glass Vessel	SC_SDF_GlassBreak
Generic	none — a neutral preset assumes no material

These are starting points on the generated profile, not hard-wired behaviour: replace them on your own profiles or preset templates like any other weighted variation.

Deterministic selection

SelectWeightedSoundVariation(Variations, RandomSeed, OutVolumeMultiplier, OutPitchMultiplier) is a pure, static, Blueprint-callable function. The same seed always selects the same variation with the same volume and pitch multipliers.

The framework uses it internally, and it is exposed so a middleware layer or a test can reproduce the exact selection the framework would have made.

Built-in playback versus delegates

Two independent switches on the profile:

Property	Effect
bEnableAudioRequests	Master switch: emit audio requests at all
bEnableBuiltInAudioPlayback	Also play the selected sound through UGameplayStatics

The request payload

FSDFDestructionAudioRequest:

Field	Meaning
Event	Which of the four events
SourceActor	The destructible
Location	World position
ImpactDirection	Direction of the causing hit
ImpactSpeed	Speed associated with the event
DestructionPower	Power of the causing hit
SelectedSound	The variation the framework picked
VolumeMultiplier	Resolved volume multiplier
PitchMultiplier	Resolved pitch multiplier
RandomSeed	Seed used for the selection
SelectedVariationIndex	Index into the profile array
bBuiltInPlaybackRequested	Built-in playback was configured
bBuiltInPlaybackAttempted	Built-in playback was actually attempted
bBuiltInPlaybackSuppressedByBudget	The per-frame built-in audio budget suppressed it

Where to listen

Scope	Delegate
One object	USDFDestructibleComponent::OnDestructionAudioRequested
Whole world	USDFDestructionSubsystem::OnDestructionAudioRequested

The component delegate fires before built-in playback is attempted, which makes it a genuine interception point. The subsystem delegate is the right hook for a global router — MetaSounds, Wwise, FMOD or your own pooled audio system.

Middleware integration pattern

1. Set bEnableAudioRequests = true and bEnableBuiltInAudioPlayback = false on your profiles.
2. Bind USDFDestructionSubsystem::OnDestructionAudioRequested once, at world start.
3. Map Event, DestructionPower and any gameplay tags from the causing hit to your own event names.
4. Post the event at Location, applying VolumeMultiplier and PitchMultiplier if you want the framework’s variation, or ignoring them and using your middleware’s own randomisation.

You can also leave the Sound arrays empty in that setup: the request is still emitted with SelectedVariationIndex = -1, which your router can treat as “no asset, use my own mapping”.

Debris impact audio

Debris collisions are throttled by three profile properties so a shattering pot does not produce thirty simultaneous clacks:

• MinimumDebrisImpactSpeed — slower collisions are silent;
• DebrisImpactCooldown — minimum seconds between debris sounds;
• MaximumDebrisImpactSoundsPerDebrisActor — hard cap per piece, default 1.

Audio budget

The world subsystem caps MaxBuiltInAudioEventsPerFrame (default 32). The cap applies only to built-in playback attempts. Requests always reach the delegates, so a middleware integration is never silently starved by the framework’s own budget.

Diagnostics through GetAudioStats return FSDFDestructionAudioStats:

Field	Meaning
TotalRequests	Requests emitted since the last reset
TotalBuiltInPlaybackAttempts	Built-in playbacks attempted
TotalBuiltInPlaybackSuppressed	Built-in playbacks suppressed by the budget
BuiltInPlaybackAttemptsThisFrame	Current frame counter

GetLastAudioRequest returns the most recent payload and ResetAudioStatistics clears the counters without touching active state.