SRS Motion Compensation will remove a motion platform movements by changing the communicated position of a VR Headset before the VR image is rendered. This will allow the VR image to remain firmly in the seat or cockpit when racing or flying instead of being moved outside of the car or cockpit when the motion platform has a large amount of movement. This will increase the immersion and improve the actual feeling of motion while in VR.
This guide provides a central location for how to install, setup, and use Sim Racing Studio Motion Compensation. It is based on the initial Beta setup guidance, SRS Blog post, the OVRMC website, user experience, extensive testing, and information directly from Sim Racing Studio. Topics include:
Supported VR Headsets
Requirements
Setup Guide
Witmotion Sensor Installation
SteamVR Installation OVRMC Installation
Initial Sim Racing Studio Configuration
SteamVR Add-Ons and Overlays
Launching OVRMC
Configuring OVRMC Settings
Enabling Motion Compensation
Adjusting SRS Motion Compensation Settings
LPF Beta values and DEMA sample Settings
Keyboard Shortcuts
Tuning Motion Compensation
Pre-Launch Checklist <- IMPORTANT: Required every time SteamVR or OVRMC is restarted
Example Settings
Troubleshooting
No OVRMC window appears when launching from the Gear icon in SteamVR
Virtual Tracker not showing in the Steam Status Window
Gear Icon for OVRMC not showing / was showing but now gone
OVRMC or SRS Motion Compensation is Blocked
SteamVR Crashed and now the HMD only shows a gray screen
Numbers next to Bullseye in SENSOR are erratic (Witmotion Sensor Calibration)
"Swimming" or "Laggy" Image
A thin yellow cross with a green line appears in the VR image randomly
Note: SRS Motion Compensation will compensate platform movement on the Pitch, Roll, Sway(Roll), and Surge axis for actuator and non-actuator platforms. Yaw(Tracton Loss), Linear Sway(Double Traction Loss), and Heave are not compensated.
Supported VR Headsets
SRS Motion Compensation has been verified to work with the following Virtual Reality (VR) Head Mounted Displays (HMD). If your HMD is not listed, SRS Motion Compensation may still work.
Windows Mixed Reality (WMR) Headsets (G2, Odyssey+, etc)
Pimax 5K and 8KX
Oculus Quest 2 (with Oculus link in SteamVR)
Oculus Rift S and CV1
Valve Index (requires OVRMC 0.3.6)
Requirements
The following items are required to use SRS Motion Compensation:
SRS Premium Add-On Subscription for the SRS Base License
OpenVR Motion Compensation (OVRMC)
SteamVR (Non-Beta Version)
Witmotion WT901C (RS232) Sensor and Witmotion RS232 USB Cable
SRS Premium Add-On Subscription
A SRS Premium Add-On Subscription is required to enable Motion Compensation in Sim Racing Studio. A SRS Premium Add-On Subscription can be purchased here or from within SRS by going to SETUP > License and clicking the Premium purchase button. This add-on subscription enables SRS to continue development on new and experimental projects and provides additional features including:
Joystick Telemetry Maker
Premium Shaking Effects
Mobile Companion to access SRS from Phone or Tablet
Pro-Tune Profile Downloads
Cloud Tune Sharing and Importing
Intellitune WIzard for Motion Platforms
Cloud Backup and Restore
Note: A SRS Base License is also a requirement as the SRS Premium Add-On Subscription is just an add-on to the Base License. You can find more information about the differences here.
OpenVR Motion Compensation
OpenVR Motion Compensation (OVRMC) is an OpenVR driver that allows the ability enable motion compensation within SteamVR. Download the latest version, currently v0.3.6, from here. OVRMC works by utilizing its OpenVR driver which hooks into the HMD device driver and allows OVRMC to modify any pose/positional updates coming from the HMD before they reach the OpenVR runtime used by SteamVR. The full OpenVR Motion Compensation website can be found here for additional information.
OpenXR is not supported at this time.
IMPORTANT: Due to the nature of this solution, the OVRMC driver may break whenever Valve decides to update the driver-side OpenVR API. It is critical the motion simulator community, this means you, continues to request that Valve with OpenVR, future development of OpenXR, or any future VR API developers supports motion compensation APIs. Please make your voice heard!
Note: OVRMC is an open source software that is based on OpenVR Input Emulator and has been primarily created and maintained by a single individual, Dschadu. Please feel free to donate to Dschadu (aka Martin Klein) via his link here as a thank you for the ability to have motion compensation in VR games for motion platforms.
SteamVR
OVRMC requires SteamVR to work as it hooks into SteamVR's OpenVR API to adjust the positioning of the image seen in the VR HMD. OVRMC will not work without SteamVR. More information on SteamVR can be found here.
Note: The current SteamVR Beta can cause the OVRMC main menu to not appear. Use the normal SteamVR version instead. Instructions on how to uninstall the beta can be found in troubleshooting at the end of this guide.
Witmotion WT901C (RS232) Sensor and Witmotion RS232 USB Cable
The Witmotion WT901C sensor and its required Witmotion RS232 USB Cable are utilized by SRS to know the precise movements of the motion platform. The specific model Witmotion sensor and cable are the only ones officially tested and supported.
The Witmotion sensor can be purchased from the following locations:
Aliexpress link here. IMPORTANT: When purchasing from Aliexpress, different models will be available on the product detail page. Only the WT901C (RS232) + RS232 Cable have been verified to work with SRS Motion Compensation. Ensure you purchase the correct Witmotion sensor and cable. An image of the correct bundle that includes both the WT901C (RS232) sensor and RS232 Cable is below:
Amazon link for the Witmotion WT901C (RS232) sensor can be found here and the link for the Witmotion RS232 USB Cable can be found here. NOTE: If purchasing the Witmotion Sensor or Cable from different Amazon country websites (ie. amazon.ca, amazon.uk.co, amazon.de, etc), ensure the exact model of the Witmotion Sensor and Cable are purchased. Images of the correct WT901C (RS232) sensor and RS232 Cable are below:
DISCLAIMER: Sim Racing Studio Motion Compensation is an experimental feature and might stop working if there are updates to SteamVR or if OpenVR Motion Compensation (OVRMC) ends development. Sim Racing Studio is not responsible for any expenses you incurred related to the Sim Racing Studio Motion Compensation feature.
Setup Guide
SRS Motion Compensation should work with any VR HMD as long as you are using SteamVR for rendering the VR image. However, there can always be issues in compatibility with the various number of headset available and their proprietary software used to communicate with SteamVR.
NOTE: Sim Racing Studio is unable to guarantee support resolution for the experimental feature of motion compensation. If support is needed, join the Sim Racing Studio Motion Compensation Discord channel here. If additional support is required, please book an appointment with the Sim Racing Studio VIP Service here.
This Setup Guide will cover the following topics:
Witmotion Sensor Installation
SteamVR Installation
OVRMC Installation
Sim Racing Studio Initial Configuration
SteamVR Add-Ons and Overlays
Launching OVRMC
Configuring OVRMC Settings
Enabling Motion Compensation
Configuring SRS Motion Compensation Settings
LPF Beta values and DEMA sample Settings
Keyboard Shortcuts
Testing the SRS Motion Compensation
Witmotion Sensor Installation
1) Place the Witmotion Sensor on your platform and tightly secure it. It should be mounted firmly on the platform. If the sensor is slightly loose, it could result in poor motion compensation. If using aluminum extrusion, M5 bolts will work, but will be a tight fit.
The Witmotion Sensor can be installed anywhere on your platform. However, the settings in this guide is based on a HORIZONTAL installation and the RS232 USB Cable is FACING FORWARD (the same direction your eyes are looking at towards the front of your platform). It is HIGHLY recommended to install the Witmotion Sensor this way as it will require the least amount of configuration later.
The Witmotion Sensor can be installed vertically or in other locations on the platform; however, some settings might need to be reversed depending on how you position the Witmotion Sensor. Details on how to reverse settings will be covered in the Configuring SRS Motion Compensation Settings section below.
2) Next, connect the Witmotion Sensor via the RS232 USB Cable to your computer via a USB port. If successfully installed, you should see a new CH340 device in Windows Device Manager in the Ports (COM & LPT) section.
If you do not see a new CH340 device listed in Device Manager, install the necessary driver from here. Note: The COM port listed will vary depending on other devices installed on your PC.
SteamVR Installation
If you do not already have SteamVR, go here to install it. Click on the 'Play Game' button to begin the installation process. SteamVR works with Vive, Rift, Windows Mixed Reality, and other PC VR HMDs.
Note: SteamVR is required for OVRMC to work.
OVRMC Installation
The next step is to install OpenVR Motion Compensation (OVRMC).
Download the latest version of OVRMC from here (currently v0.3.6).
Run the Installer.
The installer will automatically install all the files needed for OVRMC to work with SRS Motion Compensation.
Note: When installing OVRMC, you might receive a Windows warning. Please proceed with the "Run Anyway" option.
Initial Sim Racing Studio Configuration
1. Ensure you have the latest version of Sim Racing Studio. You can download the latest version of Sim Racing Studio from the downloads page here.
2. Open Sim Racing Studio and go to SETUP > Motion Compensation
3. If SteamVR, OVRMC, and the SRS Virtual Tracker are all installed correctly, you will see the Installed message in the Health Check section. If not, click the Refresh button to enable SRS to check again.
If one of the items does not show Installed, repeat the install process in the previous sections or refer to the Troubleshooting section at the bottom of the guide.
4. To verify if the Witmotion Sensor is working properly in SRS, there should be values other than 0.0 next to Pitch, Roll, or Sway that change even when at a rest as seen in the image below:
5. To calibrate the sensor to the neutral position of the platform, click on the Bullseye icons for Pitch and Roll to calibrate and save the settings.
IMPORTANT: The Bullseye icons for Pitch and Roll will need to be calibrated every time while the platform is level before you launch OVRMC to avoid any misalignment for motion compensation.
6. Skip the SENSOR section as it will be adjusted in the Adjusting Sim Racing Studio Motion Compensation Settings below.
7. In the SETTINGS section, in the Seated Height (mm) field, enter the distance in millimeters from the bottom of your seat (under the pads) to your eye level. This helps in determining the offset of how high you are sitting and where the HMD will be located. If a measurement is unobtainable, utilize the default of 1000 since it will work in most instances. The value range can be from 1 to 1200.
8. In the Installation field, if you have mounted the Witmotion Sensor vertically instead of horizontally on your motion rig, click the field and change it to Vertical. If you have mounted the Witmotion Sensor horizontally, leave it on Horizontal.
9. (For actuator platforms with horizontal surge actuators only) If you have a horizontal surge actuator, insert the stroke in millimeters in the Surge Horizontal Actuator Stroke (mm) field.
IMPORTANT: When finished making changes, click SAVE at the top right in Sim Racing Studio.
SteamVR Add-Ons and Overlays
Now that the Witmotion Sensor and OVRMC is successfully installed, you must verify that OVRMC and Sim Racing Studio are active in the SteamVR Add-Ons and Startup Overlay Apps. You can do this now or later when you are about to Configure the OVRMC Settings below.
Open SteamVR
Go to Settings
Go to Startup / Shutdown
Select MANAGE ADD-ONS
Make sure 00vrmotioncompensation and simracingstudio are listed and shown as ON. Note: OVRMC in SteamVR shows up at 00vrmotioncompensation and SRS Motion Compensation shows as simracingstudo.
Next select CHOOSE STARTUP OVERLAY APPS
Ensure that VR Motion Compensation is turned On
If everything has been setup correctly, you should see a SRS Virtual Tracker (blue hexagon with a T) listed as a tracking device in the SteamVR window as shown below.
Launching OVRMC
There are two options on how to configure the settings within SteamVR for OVRMC:
Option 1) Utilize a VR controller while in SteamVR to make changes to OVRMC
Option 2) Utilize a startdesktopmode.bat file that will allow you to make adjustments to OVRMC on your desktop instead of in VR.
Both methods will still require you to wear your HMD to see the Virtual Tracker in VR. The choice only determines how you will interact with OVRMC when making the changes either with Option 1 by using a VR controller while in VR or with Option 2 by using your mouse and keyboard on your desktop while in VR.
Note: Due to the buggy nature of the startdesktopmode.bat file's tendency to crash SteamVR, its recommended to utilize Option 1 when possible.
Option 1:
1) Launch SteamVR and activate your VR controller
2) Use the menu button on your controller to access the SteamVR Dashboard
3) Select the GEAR icon in the bottom left to launch OVRMC
IMPORTANT: You will need to initially launch OVRMC like this EVERYTIME you want to use SRS Motion Compensation.
4) Proceed to Configuring OVRMC Settings
Option 2:
1) Go