SteamVR Tracking Component

Section 6. SteamVR Tracking Component

Unlike fixed tracking solutions, SteamVR does not require a complex calibration process to run. However, due to the fact that the volume itself can change every time it is moved, making use of SteamVR for virtual production means that positions in the virtual world are never reliably the same. Therefore, we require the use of a calibration point for the position data to remain consistent. From that basis, came the current form of how we calibrate a physical screen to the virtual.                        

Section 6.11 Detailed Settings.                            

This is the primary place to get tracking up and running on ARFX Cameras.

Section 6.12 Base Settings.  

• Get Serials - Will try to automatically find and assign both the hero and calibration serial numbers. Please check out Using the “Get Serials” Button for more information.

• Patch HMD Req - Allows you to disable the HMD requirement that SteamVR has by default. Please check out SteamVR Tracking Hardware for more information.

• Hero Serial Number - The primary tracker serial ID that will track your physical camera’s position in virtual space. It can be the same as the Calibration Serial Number.        

• Calibration Serial Number - The secondary tracker serial ID that is used for calibrating your physical screen’s position and orientation in virtual space. It can be the same as the Hero Serial Number.

• Samples - The amount of data that is used to calculate velocity thresholds within 256hz refresh rate.

• Tracking Frame Delay - The number of frames to delay your tracking data by. Note that this delay is based on the frame rate of the running scene.

• Use Raw Calibration Tracking - When enabled, any thresholds will be disabled only when trying to calibrate.

• Use Hero Tracker as Calibrator - A universal ARFX tracker component setting. This allows the hero tracker to act as a calibration tracker as well. In SteamVR, it is not necessary as you can simply assign the same tracker serial to both hero and calibration, but the option is here if you wish to ensure it is using only the hero tracker.

Section 6.13 Thresholds.  

These base settings have worked in most stage setups, but depending on your stage, these need to be increased.

These settings are important to the stability of your tracking. “Tracking jitter” is the term we use when we describe a particular problem that occurs when the tracking location and orientation tend to shake or vibrate even though the tracker is sitting perfectly still. This problem is most prominent with orientations as minute variations in this data are magnified significantly on whatever is attached to this data (particularly when using SteamVR on a normal green screen Virtual Camera, you will see the view shift randomly depending on your tracking environment).

The solution to this problem was to implement velocity thresholds, the minimum amount of movement the tracker needs to make to be considered usable. The data is super precise. Thus, the values you are actually changing are the amount of precision to use in its checks.

• Disable Velocity Thresholds - This completely disables all velocity thresholds. It is not recommended unless it is for troubleshooting.

• Velocity Power Threshold - Linear movement threshold. The amount of precision used to check the tracker’s velocity data against. The lower the value, the harder it will be to break the threshold.

• Angular Velocity  Power Threshold - Rotational movement threshold. The amount of precision used to check the tracker’s angular velocity data against. The lower the value, the harder it will be for the rotational speed to break the threshold.

Important

Power thresholds are actually the value a negative power. In other words, 10^-X. So by default, ARFX's SteamVR component uses 10^-14 or 0.00000000000001 as the threshold for movement!

Section 6.14 When to Change Your Thresholds.      

If you consistently see jitter or random movement when the hero tracker is sitting still, then you may want to investigate your thresholds. However, it is best to look to your tracking volume first for anything that can cause a disruption of your Base Station’s IR signal. Check out the Tracking RoomSetup section for information on major issues that can arise within your tracking volume.

If these issues do not pertain to your tracking volume, then you will have to use the above thresholds to help mitigate your tracking jitters. Lower the value one point at a time, checking to see if you still have full movement of your hero tracker. Stop when you’ve found a value that allows you to continue movement while mitigating or eliminating disruptive tracking jitter that you had before.

Alternatively, if you’re moving, the tracker does not fully register the movement, or it only registers movement when moving fast, then you will have to increase the value of the thresholds, making it easier for the speed of the tracker to be registered as an allowed movement.

Section 6.15 The Tracker Serials.

Once added to an ARFX Camera, the SteamVR Tracking Component is where you’ll go to set up its trackers. In the past you may have had to use 3rd party software to figure out the serial numbers that indicate each tracker, but today it is as easy as pressing a button.

Section 6.16 Using the “Get Serials” Button

This button makes it a breeze to figure out tracker serials, but it does have its limitations.

In order to use this button, you must have the following ready:

• SteamVR must be running

• Your ViveTrackers must be plugged in via USB

• Your trackers must be shown within SteamVR’s status window.

• You do not need your base stations for this.

Once you click on "Get Serials", both the hero and calibration serial numbers will be automatically populated with the first two trackers it finds. If only one tracker is found, both the hero and the calibrator will be assigned the same serial number.

Important.

On first press Unreal may pause for a few seconds before responding again. This especially happens when SteamVR is not running as Unreal is trying to use an application that is not ready to do so.

The message you’ll get when getting the serials fails.

If this button fails to find your tracker serials, then make sure that each tracker is connected directly into your PC’s USB ports (avoid USB hubs!). If you are using USB extension cables, be mindful of the limits on USB cable length. It is best to use active extension cables for lengths. You know your trackers are connected when in SteamVR your tracker’s icon is no longer gray.

Section 6.17 How to Manually Obtain Your Tracker Serials.        

If you cannot obtain the right serials or you are using more than two ViveTracker’s, then you may have no choice except to use third-party software to obtain your tracker’s serial number.        

Important

Required Software USBDeview  

Click on this link to download USBDeview.

USBDeview used to be bundled along with SteamVR and is no longer due to being 3rd party.

1. Once you have downloaded USBDeview, run it.      

2. Connect your Tracker to your PC via USB.

3. In USBDeview, click on Registry Time View 1 next to Serial Number to order the list of USB devices by the time they were last connected.

4. In USBDeview’s Serial Number column, find the tracker by looking for a value that starts with LHR-

5. Double-clicking that device will open a menu that you can use to copy and paste the LHR- serial number into the SteamVR Component (Example input: _LHR-D0D5F19C_ ).  

6. If you have another tracker, plug it in next. The new tracker should appear at the top of the list of newly connected USB devices.

7. Repeat the last two steps until you are done.

Important

It is recommended to label your trackers with their unique Serial Number for ease of identification on set. It is also recommended to label which wireless USB Dongle belongs to (Label them A, B, C, etc. for example).

Section 6.18 How to Calibrate ARFX Cameras with SteamVR.    

Although slightly different, both ARFX and Multiscreen Cameras use the same basic calibration steps.

To calibrate ARFX Cameras, you first use PlayInEditor to start the scene. Using the Tab or Left Face Button on your controller will bring up the calibration UI, as shown in the image above. If your tracking is working and set up correctly, the movement of your calibration tracker will be mirrored on the green wireframe indicator on the screen.      

The correct orientation to calibrate your screen with SteamVR.  

Place the calibration tracker flat against the screen, centered on the red crosshairs. For both 2.0 and 3.0 [ViveTracker], you orient the tracker with the USB port/cord facing up along the center crosshair, as shown in the image above.    

Press C or Right Face Button on the gamepad to calibrate the ARFX Camera.

Move the hero tracker around to test your calibration. If it looks wrong or is off-center, then try calibrating again.

When you are done, press Tab or Left Face Button on your controller again to turn off the Calibration UI.

Important

It is important to have a base station in view of your screen before calibrating. Make sure not to block the view of the tracker from this base station as this could break tracking of the tracker altogether. A good way to test if you still have tracking against the screen is to move the calibration tracker around just before touching the screen. The green wireframe indicator should still track your movement all the way to the screen itself.

Section 6.19 Using the Hero Tracker.  

Once calibrated, you are free to use the hero tracker. Try moving it forward and back, left and right to see how the ARFX perspective warp works. To better understand, try placing the tracker on or near our head to see first-hand what a physical camera will record. Just keep in mind that rotations of the tracker do not matter; only positions do. No matter if you are up close or far away or on either side of the screen, your perception of what lies beyond the screen should not break.

Section 6.2 Further Optimizing the Hero Tracker’s Position.  

ARFX assumes that the position of the Hero Tracker is also the position of your physical camera’s sensor. Since this is most likely not the case, you may want to optimize your tracking position further to fix this discrepancy. You can find information on how to do this by going to the ARFX Camera Components section, which details how to use the Offset Component.

Section 6.21 StreamVR Setup in the Options Menu.  

In prebuilt, individual scenes, the main way of setting up SteamVR tracking is via the options menu.

When using SteamVR tracking, this menu can be found by accessing the Options menu while in play with either Escape, Backslash, or Start on a gamepad. The initial section, Setup, contains a section dedicated to setting up SteamVR with much the same options as found within the ARFX Pro Plugin. Changes are reflected in real-time, so adjusting, such as thresholds, can be assessed immediately rather than one change at a time.

Important

It is not recommended to use the Options Menu within the Unreal Editor. Settings saved within this menu will override any changes made outside of it within the editor. If you have made a change and would like to remove the save settings, simply go to the  History section and use the Delete All Saves button found within.

Section 6.22 Available SteamVR Settings in the Options Menu.

• Patch SteamVR - Changes SteamVR's configuration to disable the requirement for an HMD. If it is already disabled, the button will disable itself and the indicator text will change to how it is shown above.

• Hero Tracker Serial - Serial number for the hero tracker. Pressing Auto will assign the first connected tracker found (if any).

• Calibration Tracker Serial - Serial number for the calibration tracker. Pressing Auto will assign the second connected tracker found (if any).

• Tracking Delay - The number of frames by which your tracking data will be delayed. Note that this delay is based on the frame rate of the running scene.

• Use Tracking Velocity Clamps - This disables all velocity thresholds completely. It is not recommended unless it is for troubleshooting.

• Bypass Clamps for Calibration - If enabled, the calibration tracker will always use unfiltered positions

• Threshold Sample Size - The amount of data that is used to calculate velocity thresholds within a 256hz refresh rate.

• Velocity Threshold - Linear movement threshold. The amount of precision used to check the tracker’s velocity data. The lower the value, the harder it will be to break the threshold.

• Angular Velocity Threshold - Rotational movement threshold. The amount of precision used to check the tracker’s angular velocity data against. The lower the value, the harder it will be for the rotational speed to break the threshold.              

Section 6.23 Additional Tracking Settings in the Options Menu.                  

These settings are universal to nearly all types of tracking used in ARFX. In SteamVR, none of these are usually used, but the options are here regardless.

• Use Hero Tracker as Calibrator - Allows the hero tracker to act as the calibration tracker as well. Use this if you only have one tracker on hand.

• Disable Tracking While Calibrating - When the Calibration UI is on screen, all tracking made by the hero tracker is disabled. Useful for optical CV style tracking systems such as with our ARFXApp Windows App.

• Lock Tracking Rotations - Forces all trackers to maintain 0 pitch, yaw, and roll. Used mainly in calibration and assumes that the screen is flat upon the ground (will need modifiers to rectify tracking re-routing such as with _XYZ to XZY_.