add wivrn-lighthouse guide

content/docs/fossvr/wivrn/_index.md

@@ -16,3 +16,37 @@ It's very similar in purpose to [Monado](/docs/fossvr/monado/), but for standalo
 Current limitations are a fixed bitrate and network protocol streaming only, please ensure your headset is on a stable network or utilize an ethernet adapter to your headset to operate in a quasi-wired mode.
 
 Should you utilize [Envision](/docs/fossvr/envision/) for WiVRn setup, please ensure your APK and WiVRn server match as closely as possible. Check the WiVRn github [actions](https://github.com/WiVRn/WiVRn/actions) for an APK matching your server build to install to your headset.
+
+## WiVRn + Lighthouse driver
+
+This section covers using WiVRn with any lighthouse-tracked device: Index/Vive controllers, Vive/Tundra trackers, etc. Important steps are marked with 🔴.
+
+🔴 Have SteamVR installed (no need to run it).
+
+🔴 In Envision, set WiVRn Profile as such:
+- XR Service CMake Flags:
+  - `WIVRN_FEATURE_STEAMVR_LIGHTHOUSE=ON`
+- Environment Variables:
+  - `WIVRN_USE_STEAMVR_LH=1`
+  - `LH_DISCOVER_WAIT_MS=6000`
+
+🔴 Perform a **Clean Build** after changing these!
+
+If not using Envision, simply pass `-DWIVRN_FEATURE_STEAMVR_LIGHTHOUSE=ON` to cmake and export the env variables before starting `wivrn-server`.
+
+🔴 Grab [Motoc](/docs/fossvr/motoc/), this can calibrate the two tracking technologies to work together.
+
+Discovery happens only on first connection, so be sure to **have all lighthouse devices powered on and in line of sight of base stations before connecting the headset!**
+
+Once a device is discovered, it may be powered off and then back on later.
+
+🔴 Once video appears in the headset, check `motoc monitor` to make sure your devices all show up.
+
+If one or more devices are missing, try:
+- Spread the devices out more; lighthouse devices get discovered quicker if they're not piled up on each other. Simply strapping them on is good, too.
+- Increase `LH_DISCOVER_WAIT_MS`, though this delays the client on first connection.
+
+To re-discover devices, restart WiVRn server.
+
+At this point, your lighthouse devices will be randomly floating about somewhere. To calibrate them, follow the guide in the [Motoc README](https://github.com/galister/motoc/blob/main/README.md).
+