CS2 Fog Of War (CS2FOW)

Server-Side Anti-Wallhack Occlusion Culling for Counter-Strike 2

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📌 Overview

CS2FOW is a specialized Metamod plugin designed for community-run and dedicated CS2 servers. Its primary goal is to combat wallhacking by implementing server-sided occlusion culling.

The Core Logic: If a player is completely obscured by the map's solid geometry, the server simply stops transmitting that player's entity data to the opponent's client. If the client never receives the coordinates, a cheat has no data to render on the screen.

🛠️ Deployment & Compatibility

• Installation: This is a server-side tool.
• Client-side installation required $\rightarrow$ Not required.
• Works on Valve Official Matchmaking $\rightarrow$ Impossible (unless Valve integrates this logic natively).
• Impact: It does not modify local files, inject code into the player's game, or require any user-end software.

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⚙️ How It Works

The plugin acts as a gatekeeper for entity data. Instead of the server broadcasting every player's position to everyone, it performs a visibility check.

📊 Data Filtering Matrix

The current preview version focuses specifically on living combatants.

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🔍 Technical Deep Dive

Spatial Analysis

CS2FOW doesn't rely on manually created maps. Instead, it utilizes the actual CS2 map physics resources.

1. The Baker extracts static collision triangles from the mounted map.
2. It constructs a BVH8 (Bounding Volume Hierarchy) acceleration structure.
3. At runtime, the server checks multiple points on the observer and target to determine visibility.

Preventing "Pop-in"

To ensure that players don't suddenly "teleport" into view the millisecond they round a corner, the plugin uses a predictive buffer. It reveals enemies slightly before they are mathematically visible.

The reveal window is calculated based on the recipient's network latency: $\text{Reveal Buffer} = \text{RTT (Ping)} + \text{Worker Update Interval}$

This ensures that higher-ping players still see enemies smoothly, though this is capped via configuration to prevent excessive data leakage.

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⚠️ Limitations & Nuances

It is important to understand that CS2FOW is a mitigation tool, not a total cure.

• What it DOES NOT stop:
  • Sound-based cheats (footsteps, gunfire).
  • Knowledge of "common prefire spots."
  • Information from teammates.
  • Last-known position tracking.
• Gameplay Integrity: Because hit registration, damage, and movement are handled server-side, shooting through walls/doors still works perfectly. The server processes the bullet regardless of whether the client "knew" the enemy was there.

Current Technical Gaps

• Dynamic Objects: Doors, breakables, and smokes are currently not used as occluders.
• Weapon Muzzles: Currently, the plugin checks points around the body. If a gun barrel pokes around a corner before the body does, the player might "pop in" slightly late.

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🚀 Future Roadmap

The development of CS2FOW is ongoing. The following items are targeted for future updates:

• Dropped Weapon Filtering: Prevent "clutch" leaks where a weapon appearing/disappearing reveals a rotation.
• Muzzle Visibility: Add sampling for weapon bounds to trigger reveals earlier.
• Smoke Approximation: Researching volume-based occlusion for active smokes without breaking game mechanics.
• Sound Filtering: (High Difficulty) Exploring ways to strip sound data without affecting legitimate players.

// Conceptual logic for future weapon filtering
if (entity->is_dropped_weapon()) {
    if (!is_visible(observer, entity)) {
        stop_transmission(observer, entity);
    }
}