# What are occluders, and do I need them ?

<span style="color: rgb(149, 165, 166);">Basically, occluders are invisible volumes in a scene that hide everything behind them.</span>

<span style="color: rgb(149, 165, 166);">They are used for occlusion culling, a rendering feature that hides occluded objects to save performance.</span>

<span style="color: rgb(149, 165, 166);">In Enfusion, you can meet occluders in 3 basic forms:</span>

1. ****Terrain Occlusion****  
    <span style="color: rgb(149, 165, 166);">This is the most important form of occlusion culling.</span>  
    <span style="color: rgb(149, 165, 166);">It ensures that all objects which are completely hidden by terrain (for example, because they are behind a big hill) do not have to be rendered by your GPU, resulting in an FPS increase.</span>  
    <span style="color: rgb(149, 165, 166);">Since Enfusion now has an automatic terrain occlusion system, you do not have to enable terrain occlusion yourself.</span>  
    <u><span style="color: rgb(149, 165, 166);">However, when creating a terrain, terrain occlusion can still be an important thing to consider:</span></u><span style="color: rgb(149, 165, 166); white-space: pre-wrap;"> A hilly landscape will usually be more performance friendly than a completely flat one, because hills will occlude many objects.</span>
2. ****Manual Occlusion****  
    <span style="color: rgb(149, 165, 166);">Before automatic terrain occlusion was a thing, we had to set up occluders manually using WorldOccluderEntities. These were volumes placed in the world, usually within hills, to achieve the same effect as described above.</span>  
    <span style="color: rgb(149, 165, 166);">Today, these are not just no longer necessary, but also broken and won’t do anything.</span>  
      
    update (november 2024)  
    seem that bohemia abandoned the manual occlusion object, for the model occlusion to be able to place down a manual oclusion you will need to create a ghost model (bacon help me to create one and have successfuly test it)  
      
    [![image.png](https://wiki.nabla.sh/uploads/images/gallery/2024-11/scaled-1680-/w8Zimage.png)](https://wiki.nabla.sh/uploads/images/gallery/2024-11/w8Zimage.png)

[![image.png](https://wiki.nabla.sh/uploads/images/gallery/2024-11/scaled-1680-/FtAimage.png)](https://wiki.nabla.sh/uploads/images/gallery/2024-11/FtAimage.png)

here the model from bacon:

[occluder\_1kx500mx10m.fbx](https://wiki.nabla.sh/attachments/1)1. ****Model Occlusion****  
    <span style="color: rgb(149, 165, 166);">When importing custom 3D models such as buildings from Blender into the Workbench, you can set up model occluders.</span>  
    <span style="color: rgb(149, 165, 166);">These are volumes placed e. g. within large, opaque walls of houses, resulting in occlusion of what is behind these walls.</span>  
    <span style="color: rgb(149, 165, 166);">This can help with performance especially in urban areas, which may lack other sources of occlusion.</span>  
    <span style="color: rgb(149, 165, 166); white-space: pre-wrap;">Instructions of how to create them can be found </span>[<u><span style="color: rgb(149, 165, 166);">here</span></u>](https://community.bistudio.com/wiki/Arma_Reforger:FBX_Import#Occluders)<span style="color: rgb(149, 165, 166);">. If you open up XOBs made by BI in the Workbench, you will also find some good examples.</span>

<span style="color: rgb(149, 165, 166); white-space: pre-wrap;">While not essential for practical application, if you want to improve your technical knowledge on occlusion culling, I highly recommend watching </span>[<u><span style="color: rgb(149, 165, 166);">this video</span></u>](https://youtu.be/CHYxjpYep_M)<span style="color: rgb(149, 165, 166);">.</span>