OpenMW Experimental Graphics Optimizations

OpenMW Performance Override

Two experimental optimizations for OpenMW that can move you from ~50 FPS to ~100 FPS in heavy cities like Narsis and Old Ebonheart. Results vary by hardware, but on my integrated laptop I went from 30 to 50 FPS, and on my desktop from 50-60 to ~100.

Source code on GitHub

Quick Install

Note for advanced users: If you want to be minimal: copy openmw.exe and defaults.bin over your existing OpenMW install, but that install MUST be the latest OPENMW nightly. This is only for advanced users.

Linux: Use the full build.

MacOS: Use the full build.

Everyone:

1. Open settings.cfg in your Documents directory (NOT the directory with the exe). This will vary by operating system (linux/windows/mac).

2. Add these lines under the existing sections:

occlusion culling = true

shadow update interval = 2

That's it. Occlusion culling is the bigger of the two.

To remove: delete those settings, or read the Known Issues.

Configuration:

Occlusion Culling: Configuration can be done in the settings.cfg following github page's listing. It is not recommended to adjust these unless you encounter an issue and are following instructions from Known Issues.

Shadow: Configuration can (mostly) be done in game. See the Pictures tab.

BONUS

This already exists in openmw you just need to turn it on if it isn't already.

object paging active grid. It can give ~10 FPS alone:

distant terrain = true

object paging = true

object paging active grid = true

Further Recommended Pairings:

Dynamic FPS Optimization, Will adjust your view distance to keep you at your target FPS.

Jyggalagpuff's Optimizations are a good read. Miscellaneous optimizations.

What Does It Do?

The bottleneck in large cities is the scene graph — OpenMW is doing too much work figuring out what to draw and how to shadow it.

Software Occlusion Culling (MOC): Culls objects hidden behind other objects. If an NPC is behind a building, there's no reason to render them. In dense cities this can remove ~40% of the scene from the draw list, which directly translates to less work for the renderer.

Temporal Shadow Reuse: Shadows are mostly the same frame-to-frame. Instead of reca