FMOD for Unreal, Occlusion returns only 0 or 1, is no intermediate values is expected behaviour?

FMOD Studio
1

Hi,
I’m testing the Occlusion system in FMOD for Unreal and I would like to confirm whether the current behavior is correct or if I’m missing something in the setup.

I followed the official documentation:

  • Created a continuous parameter in FMOD (0–1) named exactly as the “Occlusion Parameter” in the plugin settings.

  • Automated a low-pass filter in FMOD so that the parameter value controls frequency cutoff (0 = 20 kHz, 1 = 20 Hz).

  • Enabled Occlusion on the FMOD Audio Component in Unreal (Occlusion Trace Channel set to Visibility, tested also with complex collision).

  • The parameter is local (instance parameter).

The issue:
When moving the listener around a test map, the occlusion parameter only receives values 0 or 1.
There are no intermediate values such as 0.2, 0.5, 0.7 etc.
Even when the sound source is only partially obscured by geometry, the value jumps straight from 0 to 1.

I’ve tested multiple collision settings and trace channels, but the behavior is always binary.

My question:
Is this the intended design of FMOD for Unreal occlusion (single line trace → 0 or 1)?
Or should the FMOD integration provide continuous occlusion values by default?

I want to confirm whether the plugin is working correctly, or if continuous occlusion requires implementing a custom solution (e.g., multiple raycasts and setting the parameter manually).

Using FMOD Studio 2.03.10 and UE 5.4 Thanks in advance for clarification!

2

Hi,

Thank you for sharing the information!

Yes, the behaviour you are seeing (the parameter switching only between 0 and 1) is the intended design of the current FMOD Unreal plugin.

Your setup sounds correct to me.

If you require continuous occlusion values, you might need to implement a custom solution on the Unreal side.

For sound design ideas on enhancing the perception of occlusion, this related post may offer some general ideas: How to create illusion of source occlusion with reverb

Hope this helps!