Mount & Blade II: Best engine_config.txt for Siege Performance

The objective is to stabilize the Frame Pacing during the “Breach Phase,” where physics calculations for falling debris and arrow trajectories are at their peak.

Setup & File Navigation

1. Directory Path: Press Win + R, type %USERPROFILE%\Documents\Mount and Blade II Bannerlord\Configs\, and hit Enter.
2. The Target: Open engine_config.txt.
3. Critical Safety: Before editing, ensure you have disabled “Steam Cloud” for Bannerlord, as it may revert your manual .txt changes upon launch.

Optimized “Siege Breaker” Configuration Table

Parameter	Recommended Value	Technical Purpose
number_of_corpses	20	The CPU Savior. Reduces the active physics count in choke points.
shader_quality	1 (Medium)	Lowers the complexity of blood/dirt overlays on soldier armor.
texture_filtering	2 (Anisotropic 4x)	Balanced clarity without saturating the VRAM bus ($B_{vram}$).
antialiasing_technique	4 (DLSS/FSR)	Offloads edge-smoothing to dedicated AI cores.
lighting_quality	1 (Medium)	Reduces the load of dynamic torches and fire arrows in sieges.
num_sound_channels	64	Prevents the audio engine from hogging a primary CPU core.

HowTo: Engineering the Bannerlord Engine

Follow these GameEngineer.net technical steps to maintain 60+ FPS during massive castle assaults:

1. The “Ragdoll” Protocol: In engine_config.txt, find disable_ragdolls. While immersion-breaking, setting this to 1 during 1000-man sieges eliminates the physics calculations for every falling body ($P_{body}$). If you want to keep them, ensure number_of_ragdolls is no higher than 5.
2. Sound Channel Throttling: Sieges generate thousands of sound cues (screams, steel clashing, wood splintering). By setting num_sound_channels to 64 instead of 256, you prevent the Audio Thread from competing with the AI Pathfinding Thread ($T_{path}$).
3. Cloth Simulation Overload: Every soldier’s cape and tunic is a physics object. Search for cloth_simulation and set it to 0 or false. This is the most effective way to regain FPS when you are in the middle of a dense crowd on the battlements.
4. The “DLSS/FSR” Multiplier: If you are playing at 4K in 2026, ensure antialiasing_technique is set to utilize your hardware’s upscaler. This reduces the Pixel Fill Rate ($R_{fill}$) requirement, allowing your GPU to run cooler and maintain higher boost clocks during long battles.
5. Battle Size Scaling: If you experience “slow-motion” gameplay (high FPS but slow movement), your CPU is failing to keep up with the simulation. Lower the battle size in the in-game menu to 400 or 500. This reduces the Complexity of the $O(n^2)$ AI algorithms.

Technical Explanation: AI Pathfinding and Bottlenecks

During a siege, every soldier calculates the shortest path to their target. When a gate breaks, hundreds of NPCs update their $NavMesh$ simultaneously.

$$Total\_CPU\_Load = (Soldier\_Count \times Pathfinding\_Frequency) + Physics$$

By engineering the engine_config.txt to reduce corpses and cloth physics, you are effectively “thinning the herd” of data the CPU must manage. This reduces the Interrupt Latency ($L_{int}$), ensuring that your frame rate doesn’t tank the moment the battering ram reaches the doors.