Check out this small read on Occluders, what they are, and how they can be used in game development.
A Level Designer and LD Mentor Tommy Norberg has released a great read on Occluders and Frustum Culling that will definitely be helpful for aspiring and experienced Level Designers. For those unaware, an Occluder is a special in-engine feature that prevents the rendering of objects that are in front of the player but fully covered by another object, e.g. a wall, a closed door, etc. Frustum Culling is a similar feature that stops the rendering of objects outside of a player's view cone. As you may have already guessed, these features are needed for optimization.
With just 4 images, Tommy has managed to tell about types of occluders, how to place them while developing a level, and what things should be considered in terms of level design. You can check out Tommy's short guide on occluders here or in the tweet attached above.
The author also has a great blog where he shares information about level design and game development. So, if you want to learn more about these two topics, we highly recommend visiting Tommy's blog.