# Does System::getGeometryOcclusion trace a single ray or does it to something more sophisticated?

**URL:** <https://qa.fmod.com/t/does-system-getgeometryocclusion-trace-a-single-ray-or-does-it-to-something-more-sophisticated/18469>\
**Category:** FMOD Engine\
**Created:** [March 5, 2022, 3:56am UTC](https://qa.fmod.com/t/does-system-getgeometryocclusion-trace-a-single-ray-or-does-it-to-something-more-sophisticated/18469 "2022-03-05T03:56:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Kaufel](https://avatars.discourse-cdn.com/v4/letter/k/958977/32.png) [@Kaufel](https://qa.fmod.com/u/Kaufel)\
**Post date:** [March 5, 2022, 3:56am UTC](https://qa.fmod.com/t/does-system-getgeometryocclusion-trace-a-single-ray-or-does-it-to-something-more-sophisticated/18469/1 "2022-03-05T03:56:18Z")

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The documentation about this is unclear.

FMOD\_Geometry\_SetPolygonAttributes allows to set directocclusion and reverbocclusion, and FMOD\_System\_GetGeometryOcclusion is also returning these.

What does it do internally?

Does it trace a single direct line between listener and viewer? If so does it return the properties of the first polygon hit (from the source). Does it integrate over all polygons in the path?

Or does it something more sophiticated outside of a direct line trace?

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**Author:** ![richard\_simms](https://yyz2.discourse-cdn.com/flex036/user_avatar/qa.fmod.com/richard_simms/32/261_2.png) [@richard\_simms](https://qa.fmod.com/u/richard_simms)\
**Post date:** [March 10, 2022, 2:40pm UTC](https://qa.fmod.com/t/does-system-getgeometryocclusion-trace-a-single-ray-or-does-it-to-something-more-sophisticated/18469/2 "2022-03-10T14:40:34Z")

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`getGeometryOcclusion` draws a line between listener and sound, not the viewer. It iterates through all polygons it goes through along the way, that’s why each polygon has a different level of occlusion and they can stack up.

It doesn’t work with FMOD Studio events, just Core API `channels` and `channelGroups`.

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<div class="post-metadata">

**Author:** ![Kaufel](https://avatars.discourse-cdn.com/v4/letter/k/958977/32.png) [@Kaufel](https://qa.fmod.com/u/Kaufel)\
**Post date:** [March 11, 2022, 3:38am UTC](https://qa.fmod.com/t/does-system-getgeometryocclusion-trace-a-single-ray-or-does-it-to-something-more-sophisticated/18469/3 "2022-03-11T03:38:41Z")

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Thank you for the answer!