This is a follow-up to my previous article about reducing motion sickness in sim-racing titles. The topic of whether or not the view should be locked to the horizon in sim-racing titles was hotly debated when it was first introduced years ago and this sim-racing civil war has not in any way subsided. I wanted to write this follow-up to shed some more light on the subject and hopefully bring about a ceasefire. We'll first go a little more in-depth into the the science and then talk about the pros and cons of horizon locking as well as how each individual might want to use it.
What the horizon locking setting does is mimic the way a driver's brain would see things in real life when they are looking at the track. They will see the track as unmoving because of the vestibulo–ocular reflex. This causes the eyes to rotate and move in response to signals from the inner ear to keep the image stable. In short, your inner ear knows which way is up and this tells the eyes how to move to maintain this orientation. If the driver tilts their head, the eyes will rotate to keep the track and horizon level. If the car hits a bump and the driver's head is tilted to the side with the car, the eyes will rotate to keep the horizon level.
This system works so well that it is hard to tell it is happening, but this ability to maintain steady vision is a huge evolutionary advantage. Ancient man had a much better chance of survival if they could look around while at dead sprint and still be able to spot the subtle movement of a potential predator or prey. This system is not infallible however, and there are limits. The eyes can only compensate up to a certain extent as evidenced by the head shaking example in the last article. Certain racecars and karts with solidly mounted engines can cause so much vibration through the driver's body that the driver's vision can become blurred. The inner ear can also become confused as to which way is up by mistaking constant g-loads for gravity. A pilot in a continuous banked turn can become disoriented if the eyes have no easily viewable horizon as reference. When flying in darkness, a pilot must trust their instrumentation because their inner ear can fail them as it didn't evolve taking into account constant g-loads in flight.
This system works so well that it is hard to tell it is happening, but this ability to maintain steady vision is a huge evolutionary advantage. Ancient man had a much better chance of survival if they could look around while at dead sprint and still be able to spot the subtle movement of a potential predator or prey. This system is not infallible however, and there are limits. The eyes can only compensate up to a certain extent as evidenced by the head shaking example in the last article. Certain racecars and karts with solidly mounted engines can cause so much vibration through the driver's body that the driver's vision can become blurred. The inner ear can also become confused as to which way is up by mistaking constant g-loads for gravity. A pilot in a continuous banked turn can become disoriented if the eyes have no easily viewable horizon as reference. When flying in darkness, a pilot must trust their instrumentation because their inner ear can fail them as it didn't evolve taking into account constant g-loads in flight.
Pick Your Reference Frame
The problem when taking this amazing system into the realm of sim racing is that now a driver is sitting there unmoving while the computer simulates all of this movement that their inner ear does not experience. This gives a driver a choice. If they wish to experience a track the same as a driver would in real life, they can lock the view to the horizon so it becomes the unmoving reference frame. They will see the cockpit moving around in their peripheral vision while the track remains stationary. Although it might not always be intuitive, this is how a driver experiences driving in the real world. The tradeoff however, is that the cockpit view will not match their stationary wheel and chair sitting in front of their computer.
Alternatively the driver can lock the view to the car. The car then becomes the unmoving reference frame and the world will move around it. The upside of this is that the cockpit they see on screen will match their unmoving cockpit they are sitting in. So primarily the decision of which to use will come down to what a sim driver prefers. Do they wish the real and virtual cockpits to match or do they wish the view to match what they would experience in real life. Many sim racing titles use a hybrid of these by default. Often the view will be locked to the horizon for bumps, but locked to the car for larger track geometry changes such as banking and hills. This is a compromise many drivers prefer that causes the cockpit to move around slightly in the driver's view, but the pitch and roll angles will stay relatively small.
The problem when taking this amazing system into the realm of sim racing is that now a driver is sitting there unmoving while the computer simulates all of this movement that their inner ear does not experience. This gives a driver a choice. If they wish to experience a track the same as a driver would in real life, they can lock the view to the horizon so it becomes the unmoving reference frame. They will see the cockpit moving around in their peripheral vision while the track remains stationary. Although it might not always be intuitive, this is how a driver experiences driving in the real world. The tradeoff however, is that the cockpit view will not match their stationary wheel and chair sitting in front of their computer.
Alternatively the driver can lock the view to the car. The car then becomes the unmoving reference frame and the world will move around it. The upside of this is that the cockpit they see on screen will match their unmoving cockpit they are sitting in. So primarily the decision of which to use will come down to what a sim driver prefers. Do they wish the real and virtual cockpits to match or do they wish the view to match what they would experience in real life. Many sim racing titles use a hybrid of these by default. Often the view will be locked to the horizon for bumps, but locked to the car for larger track geometry changes such as banking and hills. This is a compromise many drivers prefer that causes the cockpit to move around slightly in the driver's view, but the pitch and roll angles will stay relatively small.
Which is right for me?
The best solution will be based on what each individual wants to experience in a sim and there are going to be trade-offs either way unless you want to really spend some money. Virtual reality provides amazing presence in the cockpit so if a driver wants to experience what it looks like to really be in the car, they will want to lock the view to the car or use the default options that will just filter out bumps. This will make their steering wheel and seat match their view on screen and they will always be able to look around in the cockpit and it will look correct. This is a very viable option even if you wish to be a serious sim-racer however. This is how all sim titles were done for years and the very best sim-racers in the world can turn near perfect laps using this method.
If a driver is more interested in the view looking the same as it would in real life, they will want to lock the view to the horizon. This is also generally the preferred method if someone is susceptible to VR sickness as it will mimic how they are used to experiencing the world. This will however, cause the cockpit to move around in your view and on steep inclines and bankings this can become distracting if you like to look around inside the car a lot. We recommend if you are prone to VR sickness to concentrate on the road and not look around inside the car. It can also be helpful to turn off the in-game steering wheel if you find the mismatched movement distracting. This method also provides a benefit in that the hills and bankings will appear the same as in real life whereas the locked-to-car view acts as if the track is on a giant gimbal that levels it out as you drive. Many driver's remark that they never realized how hilly a certain track was before using the locked horizon view. This is also the method we recommend for drivers if they intend on using sim-racing as a training tool for real tracks so that what they practice in the sim will look the same when they hit the track for real.
Many sim titles often allow a driver to choose a combination of these so each individual can tailor to their own preferences. We personally like iRacing's (non-default) horizon locked solution where the view is locked to the horizon up to 30 degrees at which point it becomes locked to the car. This allows the track to look correct for banking and hills, but a wreck that sends the car flipping down the track won't cause it to rotate on the screen. This is going to be more accurate to real life anyway as the vestibular system would not be able to keep up with the rapidly flipping car.
The best solution will be based on what each individual wants to experience in a sim and there are going to be trade-offs either way unless you want to really spend some money. Virtual reality provides amazing presence in the cockpit so if a driver wants to experience what it looks like to really be in the car, they will want to lock the view to the car or use the default options that will just filter out bumps. This will make their steering wheel and seat match their view on screen and they will always be able to look around in the cockpit and it will look correct. This is a very viable option even if you wish to be a serious sim-racer however. This is how all sim titles were done for years and the very best sim-racers in the world can turn near perfect laps using this method.
If a driver is more interested in the view looking the same as it would in real life, they will want to lock the view to the horizon. This is also generally the preferred method if someone is susceptible to VR sickness as it will mimic how they are used to experiencing the world. This will however, cause the cockpit to move around in your view and on steep inclines and bankings this can become distracting if you like to look around inside the car a lot. We recommend if you are prone to VR sickness to concentrate on the road and not look around inside the car. It can also be helpful to turn off the in-game steering wheel if you find the mismatched movement distracting. This method also provides a benefit in that the hills and bankings will appear the same as in real life whereas the locked-to-car view acts as if the track is on a giant gimbal that levels it out as you drive. Many driver's remark that they never realized how hilly a certain track was before using the locked horizon view. This is also the method we recommend for drivers if they intend on using sim-racing as a training tool for real tracks so that what they practice in the sim will look the same when they hit the track for real.
Many sim titles often allow a driver to choose a combination of these so each individual can tailor to their own preferences. We personally like iRacing's (non-default) horizon locked solution where the view is locked to the horizon up to 30 degrees at which point it becomes locked to the car. This allows the track to look correct for banking and hills, but a wreck that sends the car flipping down the track won't cause it to rotate on the screen. This is going to be more accurate to real life anyway as the vestibular system would not be able to keep up with the rapidly flipping car.
The Ultimate Solution
If you have the funds and space however, you can have the best of both worlds. While using the locked horizon view, a motion cockpit that mimics the movement of the car in pitch and roll will allow the movement of a home cockpit to match what is seen on screen while also still allowing an accurate visual representation. Very high-end solutions will even allow 360 degree rotation of the cockpit so it matches the yaw of the car. Combine this with a virtual reality headset and you would have the ultimate racing simulator and probably a whole bunch of new friends wanting to visit.
If you have the funds and space however, you can have the best of both worlds. While using the locked horizon view, a motion cockpit that mimics the movement of the car in pitch and roll will allow the movement of a home cockpit to match what is seen on screen while also still allowing an accurate visual representation. Very high-end solutions will even allow 360 degree rotation of the cockpit so it matches the yaw of the car. Combine this with a virtual reality headset and you would have the ultimate racing simulator and probably a whole bunch of new friends wanting to visit.
I hope you enjoyed this article. If you are interested in a complete guide to the physics of racing, we also offer The Science of Speed book series, available through our bookstore or at popular retailers such as Amazon.
by Adam Brouillard
by Adam Brouillard
