RE4 Head Tracking

An unofficial head tracking mod for Resident Evil 4 that moves the camera with your head while your mouse or controller keeps aiming, driven by OpenTrack over UDP, with no VR headset required.

• Decoupled look and aim - head tracking moves the camera; aim stays on your mouse/controller
• 6DOF positional tracking - lean and peek with head position
• Works with any OpenTrack compatible tracker - free options available for PC, iOS and Android

• Resident Evil 4 Remake (Steam)
• OpenTrack or a compatible head tracking app (smartphone, webcam, or dedicated hardware)
• Windows 10/11 (64-bit)

Download Lopari, choose Resident Evil 4, and click Play with head tracking.

1. Download the installer ZIP from the Releases page
2. Extract the ZIP anywhere
3. Double-click install.cmd (it auto-detects your game and installs REFramework if needed)
4. Configure OpenTrack to output UDP to 127.0.0.1:4242
5. Launch the game; head tracking is enabled automatically

The installer automatically finds your game via Steam registry lookup. If it can't find the game:

• Set the RESIDENT_EVIL_4_PATH environment variable to your game folder, or
• Run from command prompt: install.cmd "D:\Games\RE4"

For placing files by hand (or installing the Nexus ZIP, which contains only the plugin files):

1. Install REFramework for RE4 (extract to game root)
2. Copy RE4HeadTracking.dll to <game>/reframework/plugins/. The mod creates CameraUnlock.ini beside it on first launch.

The mod listens for OpenTrack pose data on UDP port 4242, on every network interface. One datagram is six little-endian 64-bit floats in the order x, y, z, yaw, pitch, roll: position in centimetres, rotation in degrees, 48 bytes in total. Anything that sends that to that port drives the view. OpenTrack's UDP over network output sends exactly this, and the steps below set it up.

1. Install OpenTrack.
2. Pick a tracker under Input, using the notes below.
3. Set Output to UDP over network, host 127.0.0.1, port 4242.
4. Press Start. Tracking and the game can start in either order.

OpenTrack ships a neuralnet tracker input that reads a plain webcam. Select it under Input, pick your camera in its settings, and use the output settings above. How well it tracks depends on your camera and your lighting, so try it before buying anything.

A phone app can reach the mod directly, with no OpenTrack on the PC, if it sends the datagram described above. Point it at this PC's IP address (run ipconfig to find it) on port 4242. Not every phone tracker speaks this protocol, so check yours for an OpenTrack or UDP output option first. Headcam sends it, and I wrote it so decent tracking is free for anyone who already owns a phone.

Sending direct works when the app filters its own signal on the device. The mod's smoothing is sized to take the edge off a clean signal rather than to rescue a noisy one, so a raw feed sent direct will jitter. If it does, point the app at OpenTrack's UDP over network input on some other port, say 5252, and let OpenTrack's filters and curves clean it up before its output forwards to 127.0.0.1:4242.

Anything arriving from outside 127.0.0.0/8 counts as a remote connection and is smoothed with RemoteSmoothing rather than LocalSmoothing. That includes a tracker on this very PC that sends to the machine's own LAN address, because the mod reads the source address and not the machine.

If your device has an OpenTrack input driver, select it under Input and use the same output settings. OpenTrack's own Input list is the authority on what it can read; the mod only ever sees what OpenTrack sends.

Centring belongs to your tracker. The mod subtracts no centre of its own: it applies the pose it receives exactly as it arrives, so a stream of zeros holds the view where the game itself puts it. Press the centre control in your tracker (OpenTrack's Center bind, or the CENTER button in Headcam) and the tracker zeroes its own output, which leaves the view centred with the mod doing nothing.

That is why there is no centre hotkey here and nothing to re-centre in game. Two centres in series would drift apart, because each side re-centres at moments the other cannot see, and you would end up pressing twice to centre once. If the view sits off to one side, centre it in the tracker.

Two equivalent binding sets, use whichever your keyboard has. These are the defaults: each action's keys are a list under [Hotkeys] in CameraUnlock.ini, chords included, and any of them can be changed or removed.

Page Up / Ctrl+Shift+G turns positional (6DOF) tracking off and on. Head rotation keeps running either way.

The positional tracking choice and the yaw mode are saved to CameraUnlock.ini the moment you change them, so the next launch starts with the same choice. Toggling tracking on or off with End lasts for the session only: each launch starts with tracking on or off as EnableOnStartup says.

The mod reads its settings from reframework\plugins\CameraUnlock.ini in the game folder, and creates the file when it starts and finds none. Edit it with any text editor.

A setting set to default takes its value from Defaults.ini, which every head tracking mod that keeps its settings in CameraUnlock.ini reads. Head tracking mods that keep their settings in another file do not read it. Writing a value in place of default changes that setting for this game only. When the mod saves a setting that a hotkey changed in game, it writes the new value in place of default, so that setting no longer follows Defaults.ini in this game until you set it to default again.

Defaults.ini is %AppData%\CameraUnlock\Defaults.ini on Windows; $XDG_CONFIG_HOME/CameraUnlock/Defaults.ini on Linux, or ~/.config/CameraUnlock/Defaults.ini where XDG_CONFIG_HOME is not set, under Wine and Proton too; and ~/Library/Application Support/CameraUnlock/Defaults.ini on macOS. The mod's log, where it writes one, names the file it read.

When the mod starts and finds no Defaults.ini, it creates one holding the built-in values, unless Windows runs the game as a packaged app. The mod never changes Defaults.ini after that. Edit it with any text editor.

The built-in value of each setting set to default below:

• UdpPort=4242
• EnableOnStartup=true
• WorldSpaceYaw=true
• LocalSmoothing=0.0
• RemoteSmoothing=0.15
• PositionEnabled=true
• PositionLimitX=0.3
• PositionLimitY=0.2
• PositionLimitZ=0.4
• PositionLimitZBack=0.1
• ToggleKey=End, Ctrl+Shift+Y
• CycleTrackingModeKey=PageUp, Ctrl+Shift+G
• YawModeKey=PageDown, Ctrl+Shift+H

With every setting at its default, the file reads:

; Resident Evil 4 head tracking settings.
; Comments start with ; and go on their own line. Text after a value is part of the value.
; Hotkeys are key names such as End, PageUp or Ctrl+Shift+Y. Separate several with commas; leave empty for none.
; A setting set to default takes its value from Defaults.ini, which every head tracking mod
; that keeps its settings in CameraUnlock.ini reads: %AppData%\CameraUnlock\Defaults.ini on
; Windows, $XDG_CONFIG_HOME/CameraUnlock/Defaults.ini (normally ~/.config/CameraUnlock) on
; Linux, under Wine and Proton too, and ~/Library/Application Support/CameraUnlock/Defaults.ini
; on macOS. The log names the file it read. Write a value instead of default to change that
; setting for this game only.

[CameraUnlock]
; Written by the mod. Leave this section in place.
ConfigFormat=1

[Network]
; UDP port the mod receives tracker data on (OpenTrack protocol).
UdpPort=default

[General]
; true: head tracking is on when the game starts. ToggleKey turns it on and off.
EnableOnStartup=default
; true: yaw turns around the world's up axis. false: around the camera's own up axis.
WorldSpaceYaw=default

[Smoothing]
; Smoothing when the tracker runs on this PC. 0 is the least, 1 the most.
LocalSmoothing=default
; Smoothing when the tracker is another device on the network, such as a phone.
; 0 is the least, 1 the most.
RemoteSmoothing=default

[Position]
; true: moving your head moves the view.
; Tracking mode at startup. The mode hotkey turns it on and off and saves it here.
PositionEnabled=default
; How far, in metres, leaning left or right can move the view.
PositionLimitX=default
; How far, in metres, raising or lowering your head can move the view.
PositionLimitY=default
; How far, in metres, leaning forward can move the view.
PositionLimitZ=default
; How far, in metres, leaning back can move the view.
PositionLimitZBack=default

[Hotkeys]
; Turns head tracking on and off.
ToggleKey=default
; Changes the tracking mode: rotation and position, or rotation only.
CycleTrackingModeKey=default
; Switches yaw between the world's up axis and the camera's own (WorldSpaceYaw).
YawModeKey=default

The mod has no sensitivity, deadzone or axis inversion settings. It applies the pose your tracker sends, so set those in the tracker.

Sending a log:

• REFramework writes one log per game launch at <game>/re2_framework_log.txt. That generic name is used for every RE Engine title, so it is the right file for this game too. If the game folder is not writable it lands in %APPDATA%\REFramework\<exe name>\ instead.
• The file is truncated on every launch, so it only ever holds the current session. Attach it as-is to a bug report.
• This mod's lines are prefixed [RE4HT]. The startup sequence to look for is: Plugin loaded, Config Canonical: ..., UDP receiver started on port ..., Initialization complete, then First tracker pose received: ... once the tracker sends anything.

Mod not loading:

• Ensure REFramework is installed (dinput8.dll in game root)
• Check reframework/ folder exists with plugins/RE4HeadTracking.dll inside
• Try running the game as administrator once

No tracking response:

• Verify OpenTrack is running and outputting data
• Check UDP port matches (default 4242)
• Press End to enable tracking
• Check firewall isn't blocking UDP port 4242

View is off-centre:

• Centre in your tracker app: OpenTrack's Center bind, the CENTER button in a phone app, or SteamVR's own centring. The mod has no centre of its own, so the tracker is the only place to set one.

Jitter:

• Increase RemoteSmoothing (phone or other network tracker) or LocalSmoothing (tracker on this PC) in the [Smoothing] section of CameraUnlock.ini
• If using a phone app over WiFi, some jitter is expected - the built-in interpolation helps

Wrong rotation axis:

• The mod applies the pose your tracker sends. If an axis moves the wrong way, reverse it in your tracker's settings.

Yaw feels wrong when looking up or down at extreme angles:

• Try toggling between world-locked and camera-local yaw with Page Down. World-locked (default) is horizon-stable; camera-local follows the camera's current up-axis.

Download the new release and run install.cmd again. Your config is preserved.

Run uninstall.cmd from the release folder. This removes the mod DLLs. REFramework is only removed if it was originally installed by this mod. To force-remove REFramework:

uninstall.cmd /force

• CMake 3.20+
• Visual Studio 2022 with C++ desktop workload
• pixi task runner
• Resident Evil 4 Remake installed (for deployment only)

git clone --recurse-submodules https://github.com/itsloopyo/resident-evil-4-headtracking.git
cd resident-evil-4-headtracking

# Build and deploy to game (release)
pixi run install

# Build only (debug)
pixi run build

# Package for release
pixi run package

• Discord: Loop's Head Tracking Hangout - setup help, bug reports, and new-release announcements
• Lopari - free Windows launcher with one-click install and launch for the released head-tracking mods
• Headcam - free app that turns your iPhone or Android phone into the head tracker

MIT License - see LICENSE for details.

• Capcom - Resident Evil 4 Remake
• praydog - REFramework
• OpenTrack - Head tracking software
• CameraUnlock - Shared head tracking library

This mod is not affiliated with, endorsed by, or supported by Capcom. Use at your own risk.