Last month, we tested Cities: Skylines 2 only to discover that it runs worse than path-traced games such as Cyberpunk 2077. Forget 4K, none of our GPUs could deliver a solid 60 FPS, even at 1080p. The GeForce RTX 4090 averages 21 FPS at 4K “High,” while the Radeon RX 7900 XTX collapses at 17 FPS. At 1440p, the two flagships barely hit 30 FPS, with the averages failing to exceed the low 40s at 1080p “High.”
So, what gives? Why is Cities: Skylines 2 so taxing despite looking the way it does? The game suffers from severe LOD (Level of Detail) issues. This includes the citizens, buildings, and anything you construct. The game renders the people with a full set of teeth, eyeballs, tongues, etc, at all times, even if they’re not visible. Usually, objects like these are culled by various filters early on in the pipeline. Here, however, the developers seem to have forgotten that part.
The high (and unnecessary) level of detail, that isn’t visible to the player, everything related to these unculled meshes and textures becomes bloated. We’re talking about shadows, ambient occlusion, and other shaders acting on the in-game objects. Luckily, with a few minor tweaks, you can get a very playable 50 FPS to 60 FPS, even at 4K. On our RTX 4090, we got an average of nearly 80 FPS.
First things first. Ambient occlusion and reflections (both screen space) have a subtle to negligible impact on image quality, especially in a game like this. However, they are performance-intensive. Turn them both off. Disable motion blur and depth of field. They look ugly. Volumetric lighting is another setting that subtly affects the image (at certain times of the day) but tanks the GPU. It’s better to turn it off.
Then we’ve got global illumination. As you can guess, it lights up the scenes. Without it, everything looks darker with a lot more shadows. I recommend keeping it at “Low.” Jumping to the root of the problem:
LOD or Level or Detail. You can cut the mesh detail instead of waiting for optimizations from the developers. This offers a lofty FPS boost, but the lower you go, the more SIM-y, the game will look.
Shadows is another problematic setting. When all the meshes are being rendered at full resolution (all the time), so are their shadows. Setting it to “Low” or “Medium” would be a wise choice. Clouds and Fog are mildly taxing and can be turned off without affecting your city’s graphics quality. And with that, you should have a solid 60+ FPS at your resolution of choice (one your GPU is suited to).
You’ll find a comparison of a few other graphics settings we disabled in this Google Drive link. Using our “Optimized” settings, we set the LOD and Volumetrics to “Low” and disabled Motion Blur and Depth of Field. Unless you have a high-end GPU, we recommend disabling or lowering the settings mentioned earlier.