Motion Platforms in VR/XR – Use Cases, Benefits, and Implementation
Motion platforms are used to simulate the ability to physically move in space and to create a realistic sense of motion. One well-known example of a motion platform application are professional flight simulators, but there are many other industries that can benefit from using them as well. But what kind of motion platforms are out there, how can they be used with mixed and virtual reality and what are the benefits of adopting them?
Understanding different kinds of motion platforms
There are several kinds of motion platforms that can be used with virtual and mixed reality. Although flight simulators used in pilot training are probably the best-known example, motion platforms are not limited to just pilot training. They can also be employed for use cases such as sim racing, professional driving simulators, ship simulators and other use cases where you need to convey a sense of rapid movement.
Motion platforms can have either three degrees of freedom (3DoF) or six degrees of freedom (6DoF). 3DoF platforms offer movement along three axes (up-down, left-right, forward-backward), whereas 6DoF motion platforms also add rotation around these axes (roll, pitch, yaw).
3DoF platforms are often used in sim racing and other kinds of driving simulators, as they provide movement on three axes, which is sufficient to simulate movement of a car and things like bumps on the road, but there is usually no need to add rotation. On the other hand, flight simulators require 6DoF platforms to enable rotation along with positional movement.
In addition to being split between three and six degrees of freedom, motion platforms can have very different price points and levels of complexity and quality. The prices of these systems typically range from four to six figures (in dollars) depending on the desired capabilities. For example, the simpler platforms only support fairly limited movements whereas the more expensive motion rigs allow the user to experience more extensive movements.
Motion platforms increase immersion and training effectiveness in VR and XR
The biggest benefit of using motion platforms in virtual and mixed reality scenarios is added immersion. This is because without a motion platform, a person typically moves around in a virtual training scenario virtually while remaining physically stationary. So while the trainee’s brain gets stimuli that the person is moving, their physical body is not registering that same sense of movement. A motion platform provides this sense of physical movement to the body as well, which considerably enhances the realism of the training exercise. It also has the added benefit of reducing motion sickness that is caused in some trainees by the discrepancy of the brain perceiving that the body is moving when it physically isn’t.
A motion platform also enhances the realness of the simulation by more accurately reflecting real-world conditions, making the training more effective. This is because when you physically move, your ability to operate a control stick or other kinds of control panels and instruments is going to be affected by the movement. For example, when a flight simulator physically tilts the trainee, they get a more realistic experience of controlling the aircraft than they would in a simulator that is always flat (which does not accurately represent real flight conditions).
What to take into account when adding a motion platform to a VR or XR scenario?
What kind of movement needs to be supported?
When adding a motion platform to a VR or XR scenario, the first thing to determine is what kind of movement you are trying to simulate. Will three degrees of freedom be enough – which works for most driving simulations – or will you need six degrees of freedom (common in flight and maritime training)?
Next, you need to determine what kind of complexity you need from the platform. For example, with driving simulators the cheapest solutions might only add a sense of vibrations, but you need more complex solutions if you also want to have positional movement. Similarly for flight simulation, the simpler platforms will have more limited angles for rotational movement, whereas more complex and expensive systems can support more complex movements.
What are the space and portability requirements?
You also need to take into account what kind of portability you need and what kind of physical space you have available. The more complex motions you want to simulate, the more the actual motion platform is going to weigh, and the more space it will take.
This means that a platform that supports very complex motions is also going to be far less portable, and will most likely require a larger space to operate in. For example, while acceleration and deceleration are quite hard to simulate with a motion rig, there are platforms that can do that to an extent, but they also take up more space.
How to integrate a Varjo VR/XR headset with a motion rig?
To use a Varjo headset with a motion platform, you need to take the movements of the rig into account and pass them to the headset. There are two options for this: you can have that tracking setup outside or inside the platform.
Phiaro’s modular mixed reality chassis uses ART optical tracking in conjunction with LP Research tracking
Tracking outside the platform
Setting up the headset tracking outside the motion platform is usually the easier option, as you can place base stations outside the motion rig and they can remain stationary while the platform moves. However, to accurately take the motion of the platform into account, so that the headset displays things correctly with this setup, motion compensation needs to be used.
Motion compensation can be achieved in two main ways. One option is to employ external trackers (such as HTC puck trackers that track the orientation of the platform) that provide the information about how the platform is moving and rotating, which can then be passed to the headset. The other option is to use IMUs (inertial measurement unit) that measure the motion which you can then utilize for motion compensation. IMU is an electronic sensor composed of accelerometers, gyroscopes and magnetometers that measures a device’s velocity, orientation and gravitational forces.
Passing the information from the application to the headset is usually done through APIs. Varjo provides a third-party tracking API, a sample code for Motion Compensation plugin in the SDK, and other guidance on how to develop your own plugin for motion compensation.
Tracking built-in to the platform
The second option is only available on some motion platforms. The more advanced platforms can precisely track their own movements and pass that data to an application that can then pass it to the headset.
In this scenario, there is typically no need for separate motion compensation since the tracker moves physically with the platform and headset. IMU units are built into some motion platforms. With this setup, the data of the movement travels from the platform directly to the application. For application and system developers at motion platform companies, Varjo offers a useful sample plugin in our native SDK.
Want to leverage a motion platform in your VR or XR scenario?
If you are interested in using a motion platform as part of your virtual or mixed reality application, but aren’t sure where to start, our team of experts is happy to help you find the right solution for your needs.
Get in touch so we can discuss your potential use case further:
Learn more about Varjo implementations utilizing motion platforms:
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