Impact Main Page API Reference Change Logs
Impact Tags Impact Tag Library Using Impact Tags
Impact Manager Material Mapping
Impact Materials Impact Material Interaction Sets
Impact Interactions Audio Interactions Particle Interactions Decal Interactions
Impact Objects Impact Object Single Material Impact Object Rigidbody Rigidbodies With Multiple Materials Impact Terrain
Impact Triggers Physics Triggers Impact Collision Trigger Impact Slide and Roll Trigger Impact Simple Collision Trigger Impact Speculative Collision Trigger Impact Particle Collision Trigger Other Triggers Impact Raycast Trigger
Extending Impact Custom Impact Triggers Interaction Data Custom Impact Interactions Impact Interactions Interaction Results IInteractionResult IContinuousInteractionResult Custom Impact Objects Custom Impact Materials Custom Impact Tag Libraries
FMOD Integration Setup FMOD Audio Interaction FMOD Parameters Notes

FMOD Integration

Impact features an optional package for integrating with FMOD. This allows you to utilize FMOD for playing audio interactions, rather than using Unity's built-in audio clips and audio sources.


First, you will need make sure you have downloaded and set up the FMOD for Unity package. You can get this package from either the FMOD site or from the Asset Store.

Next, you will need to download and import the Impact FMOD Integration package, which you can downloaded here.

FMOD Audio Interaction

The Impact FMOD integration package is very lightweight and only introduces one new asset: the FMOD Audio Interaction. This is simply the FMOD-ified version of the default Audio Interaction. You can create a new FMOD Audio Interaction by going to Assets > Create > Impact > FMOD > FMOD Audio Interaction.

The FMOD Audio Interaction has the following properties that relate to FMOD:

  • Collision Event – The FMOD event to trigger when processing single-impact collisions. This event should consist of one-shot sounds.
  • Slide Event – The FMOD event to trigger when sliding. This event should have looping sound(s).
  • Roll Event – The FMOD event to trigger when rolling. This event should have looping sound(s).

FMOD Audio Interactions also share the following properties with the default Audio Interaction:

  • Velocity Range – Input velocities will be converted to a normalized (0 to 1) value based on this range and the Collision Normal Influence.
  • Collision Normal Influence – How much the input normal will effect the calculated intensity of the collision. This can be used so that grazing collisions will have a low volume even if they have a high velocity.

FMOD Parameters

Impact interactions send various parameters to FMOD to let you control your sounds:

  • Intensity – A 0 to 1 value representing the intensity of the collision. This is calculated by normalizing the collision velocity relative to the Velocity Range, and also takes into account the Collision Normal Influence.
  • Velocity – The real velocity of the collision, with no modifications.
  • CompositionValue – If using Material Composition, a 0 to 1 value representing the influence of the material at the contact point. If not using Material Composition, this will always be 1. You could use this value to scale the volume of your sounds, so that a higher composition yields a louder volume than a lower composition.
  • InteractionType – An integer number that represents the type of interaction. The built-in triggers use the following values:
    • 0 = Collision
    • 1 = Slide
    • 2 = Roll
    • 3 = Simple (i.e. no velocity or material data. Intensity will always be 1 and Velocity will always be 0.)


When using the Impact FMOD Integration, there are a few differences in how certain Impact properties affect the audio:

  • The Default Audio Pool Size property on the Impact Manager, as well as the Pool Size property on the Impact Audio Pool itself do not affect FMOD Audio Interactions. Instead, you should be using settings such as Max Instances and Cooldown on your events in FMOD Studio to limit the number of sounds played.
  • The Priority property on Impact Objects do not affect FMOD Audio Interactions. Instead, you should be controlling the priority using the Priority setting on your events in FMOD Studio. This is not to be confused with the High Priority property on Impact Triggers, which will still be in effect.