If I understand you correctly, you’ve already got the transparency part working and are now wondering how to get all walls in a certain radius around the player.
To get all objects in a certain radius around any position in the world, you can use the SphereOverlapsActors node.
You can then iterate over all Out Actors to turn them transparent.
The important part is the Object Types array you feed into the node. By default, all static meshes use the WorldStatic Collision ObjectType. You can edit this parameter in the viewport’s Details panel. You’ll need to change the CollisionPresets to Custom first to make it editable.
Seeing how you probably only want some of your static meshes to become transparent but want all of them to use the same collision, your best bet is probably to create a new Collision setting:
- Open the ProjectSettings
- Open the Collision tab, click New Object Channel and give it a name
- Back in the viewport, you can then pick your new object channel in the Collision category. If you have several objects selected at the same time, you can bulk-edit the property for all of them
Good luck!