Building a Freetrack Rig

From Hoggit: DCS World Multiplayer
Jump to: navigation, search

FreeTrack is one of many Third Party Peripherals that will greatly improve the user's experience. Crispy has put together a great step by step guide with pictures here and is currently migrating that information here.

This section is currently under construction.

A completed FreeTrack 3 point model.


[edit] Required Components and Tools

  • Compatible webcam, a list can be found on the FreeTrack website
  • 3 Infrared LEDs, wide viewing angles are preferred. The SFH 485 P is highly recommended for this application.
  • Resistor sized to run the LEDs at approximately 75% max current
  • DC Power supply--battery clip holders, cell phone chargers, and USB ports are common sources
  • Infrared Pass Filter (See Building_a_Freetrack_Rig#IR_Pass_Filtering)
  • Hat
  • Soldering Iron
  • Wire strippers
  • Solder
  • Wire
  • Electrical Tape
  • Heavy Duty Paper Clips
  • FreeTrack Software

[edit] Modifying a Webcam

The infrared filter (red square) from a Microsoft VX-3000 webcam before removal.

The most expensive part of building your own FreeTrack system is the webcam. Naturally, it's going to be permanently modified in a voided-warranty type fashion. Done correctly, removing the IR filter will have little to no impact on the functionality of your webcam. It's recommended that you search Google and the FreeTrack forums for a guide specific to your webcam, the process below is generalized and may differ with each camera.

Removing the filter

First open the webcam's plastic housing by removing all screws, some screws may be hidden behind rubber plugs. Be careful opening the housing, as some cameras are held together by fragile snap clips that will break if forced. Once separated, locate the IR filter; it will appear to shimmer between red and blue with varying viewing angles. For some cameras, the filter is hidden inside the lens assembly, for others, it is readily accessible at this point. Be cautious if the lens assembly (pictured) needs to be removed to access the filter, as the camera's CCD is located underneath, and any dust or scratches would irreversibly damage the camera.

Once the filter has been located, remove with an X-ACTO knife or similar tool. Try to avoid breaking the glass filter as any shards or dust would have to be carefully removed. Once the filter is removed, reassemble the camera and test it to make sure it still works!

[edit] Creating the LED Point Model

Recommended 3 point cap model dimensions per FreeTrack forums.
This partially completed FreeTrack model will incorporate 3 LEDs in series with a resistor.

Building the point model will require basic soldering skills and electrical knowledge. This step will take approximately 60 minutes.

A completed FreeTrack 3 point model.

Wiring the LEDs is a simple process that will vary slightly depending on the power source. Cut and strip wires of appropriate lengths to match the hat you wish to use. You'll need 4 wires about 8 inches long each. It's better to have longer wires to allow for more flexibility in LED placement. Solder the wires and LEDs and test placement on the hat. The preferred model for a baseball cap has two LEDs at the forward edge of the bill and a single LED near the top.

LED placement is somewhat arbitrary as we'll measure the distances and input that information into the software during configuration. However, for optimal performance, ensure the top LED is farther back than it is tall relative to the two forward LEDs. Neglecting this will cause poor performance when looking down.

Note: It is generally considered poor practice to wire diodes in parallel.

Alternatively, folks with access to a 3D printer can utilize this cap model designed by Crispy in conjunction with the previously mentioned electronics for a high quality point model.

[edit] IR Pass Filtering

To isolate the infrared light from the LEDs, it is necessary to filter out all visible light. This is achieved by using an infrared pass filter, which appears transparent to infrared light while opaque to other wavelengths. The IR pass filter will be affixed to the front of the webcam such that no visible light can reach the lens.

Photography Filters

An infrared pass photography filter.

Infrared pass photography filters provide the best filtering available. These filters are designed for professional photography and clearly state their cutoff wavelength. Note: The listed cutoff wavelength must be less than the wavelength the LEDs are emitting i.e. 850nm infrared filter with 880nm LEDs will work. Approximate cost is $5-10 for a new filter on ebay or amazon.


The magnetic film inside a standard floppy disk can function as an infrared pass filter. Simply cut a circular piece of the film and tape over the lens.

Multiple layers of developed film may be necessary. Like the floppy disk film, circular cutouts should be stacked and taped to the front of the webcam and block all visible light.

[edit] Software Configuration

Configuring the FreeTrack software with DCS: World will take approximately 60 minutes. Future adjustments will likely be needed for optimal performance.

If you haven't already, download the FreeTrack software from their website here. Install the software, plug in your modified webcam, turn on your LED power source, and launch the application.

When first launched, the software is not connected to the camera. To initiate the connection, select the appropriate device in the "Source" dropdown menu, and click start. When your LEDs are pointed towards your camera, you should see three red dots in the view box, and the head model on the left should rotate as you move your LED model. Some other interesting parts of the CAM page is the current FPS and JPS "Jitters per second" near the bottom right. Higher JPS is bad since the software has difficulty tracking when the points are jittering.

Let's start configuring!

CAM Page

Click the camera button

Enable B/W Mode in the checkbox under extra control

Reduce Sharpness to 0

Set contrast to max

Play with brightness, gamma, and hue until you have a clear feed of your 3 LEDs on the black/red camera screen

Turn off autoexposure and/or reduce it to 0

Set camera to outdoor mode

Click Save/apply.

Play with the threshold slider just above the source dropdown menu between changes to find suitable settings.

Frame Rate tab

Recommended 30fps, additional frames takes more bandwidth without much performance gain.

Point Size tab

Change the minimum and maximum pixel size depending on the brightness of your LEDs. If you see three huge circles on the camera, you should increase the maximum pixel size. Don't set minimum pixel size below 5ish or you might start running into issues with stray light triggering as a tracking point.

Profile Page

Here you can set the sensitivities for each degree of freedom, starting out you'll want a fairly high amount of smoothing, with sensitivities set to 1. You'll want to refine this as you get used to your new headtracker. You can set a new default for DCS World and it'll load the profile when DCS World is launched.

Output Page

Make sure FreeTrack interface and TrackIR interface are both checked.

Curves Page

This will let you define non-linear motion curves for real fine tuning--leave this alone for now.

Controls Page

The most important thing in here is the hotkey for centering FreeTrack. I believe the default is shift F12.

Model Page

Last but certainly not least, the model tab. Here you'll need to input the dimensions of your point model into the program. All measurements are in mm. If you're not using the 3 point hat model, you can select the 3 point clip model in here. The model position is the measurement from the center of your head to the top LED on the cap model and the middle LED on the clip model.

You're not quite done yet, but you're close!

A few files need to be added to the DCS: World folder in order for it to utilize FreeTrack.

Until I have a moment to finish the writeup, reference this forum post:

[edit] External Links

FreeTrack website

SFW 485 P

FreeTrack Software

3D Printable Cap Point Model by Crispy001

Personal tools