FS2 + VR + Motion "Blog"

[Spit40]

I’ve been so captivated flying FS2 with Oculus Rift that 2 months ago, in pursuit of even more of a sense of realism, I purchased a motion platform. I mentioned this on the Steam forum and promised I’d write a review after several people expressed interest in my experience. In fact FS2 has prompted so much interest in motion platforms on this and the IPACS forum that other simmers with many more flying hours than me have commented that they’ve never seen so much discussion on the subject. I think this reflects the addictive immersive quality of VR flight sim when powered by such convincing software.

This post is quite long. I've structured it as follows:

1. Have Flight Sim and Motion Platforms Come of Age?
   
2. Teething Problems
   
3. How can a motion platform possibly cope with flight sim?
   
4. So what’s it like? Is it Worth the Trouble ?
   
5. Tips and Advice (So Far)

So why is this post not titled “Review”? Quite simply because, 2 months later, I’m still not completely there. It has been quite a journey of discovery. Yet I have in the last week had some big steps forward so I thought it was time to share what I’ve learned with others who may be considering this option. I've called it a blog as I'm sure I'll have more to share in the coming weeks and months.

First here's a photo of my new platform[ndgrad.co.uk] The bits of wood and heavy metal weight are to do with me being tall and the centre of gravity issue mentioned later on.

Have Flight Sim and Motion Platforms Come of Age?

If you search YouTube for “flight sim motion platform” you’ll find quite a few interesting videos, but most of them show enormous wooden DIY creations occupying a whole room or expensive looking semi-professional simulators. In fact, when I started my research around October 2016 the entry level was pretty high and there was really no top end to what you could pay. In contrast motion platforms for serious amateur sim motor racers are a fairly well recognised upgrade path and quite a few consumer versions exist starting from around £3k. This was beyond my budget though.

Not only was it too expensive, but during my research I learned that the affordable (v. professional) simulators used by amateur racers are not ideal for flight sim. It comes down to degrees of freedom or DOF. We all understand pitch and roll. That’s two DOFs. There’s also yaw which we know and another three: surge (accelerating and braking), heave (being lifted up or down) and sway (shifting sideways). Here's an illustration I found online[www.calqlata.com]

With high speed frenetic motor racing a driver can have a lot of fun being thrown about with small aggressive amounts of roll (on a bend) and surge (accelerating and braking). Small amounts of pitch can actually feel like surge, as the seat is pressed into your back, and mechanically it’s quite a simple solution to produce a 2DOF pitch and roll simulator so that has become the norm. In flight sim, with large but gentler angles of movement and at least as much of a sense of yaw and heave as the other DOFs, I didn’t want to spend a lot of money and feel dissatisfied with the result. If you ask a motion platform expert what you need for flight sim, which I did, you’ll be told that ideally you need the full 6 DOFs, which will set you back an arm and a leg or several years of your life on a DIY project if you’re up to it, which I wasn’t.

Fortunately what I also found during my research was a lot of new entrants in the motion platform industry. Often they’re small businesses with kickstarter like approaches to getting going, and much of the impetus seems to be coming from VR. Not only that but the emphasis was no longer solely on racing, but also on flight or space sims. Sadly there are no cheap 6 DOFs to be had and also many of these new businesses are still at the promotional video stage, but it is nevertheless encouraging. Amongst the newcomers that appealed to me were RacingCube (still in development) and DOFReality who were actually shipping a 3DOF simulator.

Here’s the bottom line to this section - $999. The price of a top end GPU. Actually the 3DOF which I got is $1,499 but DOFReality.com do offer a $999 2DOF. Shipping costs a couple of hundred dollars or so more, but essentially I had found something in my price bracket.

Teething Problems

The main problem I’ve had since the platform arrived early February is the interface with FS2. DOFReality and many of the newcomers rely on a community developed motion simulation software application called SimTools – see www.xsimulator.net for more information. People write plugins for their hardware and other plugins to get telemetry data from the game. Unfortunately the telemetry plugin for FS2 broke around mid February and was only fixed a week ago. Will this happen with every FS2 update? Torsten (IPACS) explained to me what the problem was in the end and based on that I’m reasonably confident it will stay fixed.

There have been a few other teething problems I’ve been working through over the last couple of months. Some I have solved, while others are work in progress.

1. Centre of Gravity. A lot of racing simmers have heavy metal force feedback hardware and pedals which put weight forward on the platform. My VR setup is pretty light weight and as a result centre of gravity was fairly balanced. This created a problem with gearing slack, because any movement of the centre of gravity from front to back resulted in very noticeable shift as the weight switched from pressing down on a gear to lifting up off a gear. The DOFReality guys said they’d look at centre of gravity options for flight sim. I fixed the problem by adding weight to the front.
   
2. The gearing slack also affects my 3rd DOF, which is yaw. It shows up most on take off or landing with rudder applied. The yaw shift isn’t happening at the right time and is quite jerky. I’m working on taking up the slack by using springs to keep tension in one direction.
   
3. One aspect I’m slightly concerned about is the feeling of the gears turning as you bank or pitch. It isn’t noisy but also isn’t as smooth as I’d like it to be. It feels a bit crunchy and mechanical rather than the sense of moving freely in air. I went for the budget consumer version of the DOFReality platform. There is a pro version with higher quality motors for $500 more, so I’m trying to find out if I’d have been better with those. I can actually mask the feeling almost completely by adding bass transducers to the platform which are a great low cost addition anyway. They give a nice engine rumble vibration. You don’t need the branded ButtShaker. I looked up bass shaker on Amazon and picked 2 up for £20 each and spent another £20 on a basic 100watt amplifier. This is not a solution for you glider pilots I’m afraid.
   
4. The last snagging point is something I can’t do anything about yet. It’s to do with motion tracking. As a simple illustration consider a roll. The platform moves my head to the side which is detected by the Rift’s sensor and the headset accelerometer, but I haven’t moved my position in the cockpit, so how does the VR system know what is going on? No VR system properly handles this yet, although it is technically possible using motion cancellation algorithms. The Rift used to handle it quite well actually. The trick was to mount the sensor to the platform. Even though the headset’s internal accelerometers detected head movement, the tracking system gave priority to the sensor and it worked quite well. Rift updates have since stopped this working, so the best approach is now to mount the sensor off the platform – the only option for Vive anyway. The net effect is not ideal, but neither is it awful, unless you make a dramatic turn and then you can end up half way through the aircraft’s fuselage. With small movements its quite subtle and not quite irritating.

Here's another iccy of the platform showing the 3 motors and one of the bass shakers[ndgrad.co.uk]

How can a motion platform possibly cope with flight sim?

This has been an interesting area of learning and its one in which VR has made motion platforms more appealing for flight sim than they were pre-VR. The solution relies on the fact that the body is much more sensitive to movement forces than it is to detecting absolute angles, especially in VR. So if I start banking and then hold a bank angle of 20 degrees, I want to feel the initial force of banking but don’t need to be held at 20 degrees to believe that’s what’s happening. In fact that would be unrealistic anyway as a co-ordinated turn would impose no force after the initial sensation other than a stronger gravitational force.

It turns out (sorry for the pun) that this is implemented quite easily by capturing not absolute roll data but degrees/second rate of roll and mapping the platform’s roll to this rate. Once you’ve reached a steady bank angle, the platform gently returns to neutral. This of course solves the barrel roll problem which most people think is a show stopper for motion platforms. The same approach is needed for yaw, as even though I have a yaw DOF there is obviously a limit to how much I can turn. I’m actually still experimenting with what gives a nice feeling.

In terms of pitch I’ve experimented with absolute pitch and rate of pitch. I find absolute pitch works fine. It’s nice to feel pointed uphill or downhill a bit.

So what’s it like? Is it Worth the Trouble ?

I’ll tell you more later as I’m just now getting properly into platform tuning. Incidentally this is what the tuning screens look like[ndgrad.co.uk]. The first one shows how game data is captured. You can see how yaw varies between +/-180 degrees for example. Most numbers in fact will vary according to the aircraft used, especially something like rate of turn. The technique is to do a flight, capture the max/min values and then these become your 100% range of movement, which you then fine tune. You probably won't want all forces to produce 100% movement of an axis though (see later where I talk about heave) so you then decide how much movement you want each force to produce. See how this is done.[ndgrad.co.uk]

Although I’m not quite happy with the feel of yaw on the ground, I have over the last two days had some very enjoyable flights which have given me a convincing sensation of being in an airborne object. Cranking up the side wind is much more fun now and after pulling off a short field landing yesterday with a strong cross-wind I was just buzzing. There was a strong sense of wrestling with the wind and the combination of feeling the roll and yaw as I made corrections to line up with the airfield gave a convincing feeling of the lightness and physicality of the aircraft (C172).

One of my favourite parts of a flight now is touchdown. There really should be a penalty for a clumsy heavy landing and by tuning the platform right you can get that physical feedback. The trick is to carefully map the heave DOF to pitch movement on the platform so that as you touch down you get a sudden short movement of the seat pitching back which lifts the seat and so feels like a thump in the back side – in proportion to how heavily you land.

Tips and Advice (So Far)

Personally I’m very glad I went for the 3DOF platform with yaw as opposed to 2DOF. It would be nice to have a proper heave function as a 4th DOF and I’m trying to persuade the developer to make it as an add-on. Incidentally DOFReality.com do sell the yaw as an add-on to the basic 2DOF $999 platform. I would also recommend watching out for RacingCube releasing their 4DOF platform (see www.fasetech.com) as they claim it will be affordable. This platform also uses the SimTools software.

If you’re using SimTools with the AeroFly FS2 plugin, be aware that the roll DOF is actually broken. It doesn’t matter as the DOF called Extra2 (roll/sec) is the one you want anyway. This confusion cost me a lot of forum posts and lost time.

When tuning you need to fly in 2D with a monitor screen before you switch to VR. You need to be able to monitor how the movement axes (essentially the motors) are behaving (using the virtual axis output) while you fly as you simply can’t tell what’s happening in VR.

If you want to read more about SimTools, see https://www.xsimulator.net/ (search for aerofly to find the FS2 plugin thread)

That’s all for now. I’m probably at the Steam limit for a post anyway. I’ll add more as I fine tune the platform, and as the sensor tracking issues progress.

[james7347]

Great Post mate. Something I have been thinking about getting into, Thanks for the info.

[RocketMonkey]

Hi there, a very interesting post.

Regarding point 4 (the motion tracking): The makers of the Pagnian/Next Level Racing Motion Platform (Motionsystems.eu) have included something called "VR Headway" into their software - it effectively cancels the component of head movement caused by the platform movement.One has to enter the distance and offset of the VR headset vs the pivot point - and it works! In rolls the vantage point stays still, yet one can still move the head side to side like normal. One can even adjust the degree of compensation by changing the distance.
In my opinion the way to go is stationary tracking, and let the software handle motion compensation.

[Spit40]

@D3RG... that's good to know about NLM. I'm sure the SimTools community will do something similar even if Oculus don't build it in as standard. In SimTools discussions i was told the following.

"Palmer [Luckey] ruled out motion cancellation for the Oculus SDK very early in the game, which is a real shame. VectionVR created and released a modified Oculus runtime to allow for motion cancellation, but it never took off as it required devs to compile support for the mod.

There are still efforts being made to create a way to do generic motion cancellation: https://github.com/matzman666/OpenVR-InputEmulator/issues/4#issuecomment-297819958

The more VR grows for simulation the greater the need to develop a generic approach to motion cancellation."

[MarkCl]

I have read this with great interest. I was following aerofly since the early days but was put off by lack of support (and the known limitations of the early aerofly) from d-box motion platform developpers for aerofly. thanks for pointing to Simtools. your blog is a treasure of information.

[Spit40]

@david - much appreciated. This technology is a bit "bleeding edge" so I'm happy to share what I've learned the hard way with others.

[Fluke]

Great post. I am currently waiting for my 3 dof to arrive. I already have a rift and have been running various flight sims in my Obutto with a modified seat fitted with vibration motors. I am hoping the 3 dof will add more immersion and will be following the development of the add on 4th dof with great interest.

I believe Igor is working on a low cost 6 dof platform, but is some months away from a final design.

[Spit40]

@Fluke. Yes, that 6DOF looked amazing and even more so if priced affordably. Radioproffi hasn't been too encouraging yet on the prospect of a 4th, so in the meantime I'm going to take the lid off the control box and see if I can add one of my own, probably a G-Seat style heave.

[Spit40]

Motion Cancellation Update

Good news regarding VR motion cancellation for people with SimTools platforms. The xsimulator community are testing a motion cancellation plugin which seems to be working OK. It works by mounting a hand controller to the platform so that the cameras/sensors can determine exactly how the platform is moving and "subtract" that from how the head is moving.

Its for OpenVR (=SteamVR), so primarily for Vive, but Rift users can run FS2 in SteamVR mode, so that's something for me to try this weekend.

See: https://www.xsimulator.net/community/threads/vr-motion-cancellation-time-to-test.10241/

[Spit40]

Having fun now!

I've made a lot of progress with the teething problems that I listed in the opening post to this thread. In fact I'm really starting to enjoy this platform now. It certainly adds an extra dimension to VR, and I've been jumping in to some aircraft again that I don't normally fly just to more fully enjoy the different feel they have - like the Corsair for example.

The breakthroughs have come in 3 different areas: motion cancellation, simtools tuning and hardware tweaks.

Motion Cancellation
The software I referred to in the previous post works, well most of the time. This solves the problem of staying fixed in the cockpit when the platform moves. You do need a vive/oculus controller fixed to your seat which the cancellation software tracks the movement of. This allows the software to know whether you've deliberately moved your head to the side as opposed to the seat moving and you staying still. In my experience the tracker communication to the cancellation software can glitch now and again, in which case you'd see the cockpit move when you bank to the side. Its not often though and this is just v1 of the software plugin.

SimTools Tuning
SimTools is the open source software that takes the physics data from FS2 and decides how the motors driving the platform should move in response. It is very user configurable as it's used by lots of DIYers who've built their own platforms in different ways as well as a few commercially available platforms. Pitch is an easy one. Pitch up and you want the seat to tilt back. Pretty straightforward unless you want to do loop the loops, in which case you need a variation of the technique I'll describe for banking.

With banking what I was trying to achieve was that as I start to bank to the right say I feel the seat roll over to the right, but once I achieve say a 20 degree bank angle which I hold for a while I wanted the seat to imperceptibly return to neutral. I don't actually want to be keeled over at 20 degrees during the turn as its not what I'd feel in real life due to the g-force. By returning subtly to neutral it means I could then choose to bank more strongly to say 30 degrees and again feel the tilting force even though the platform was already maxed out at 20 degrees. I finally achieved this today after spending some time gaining a proper understanding of the washout gain/return functionality in SimTools. More info here if you're interested.[www.xsimulator.net]

By the way you don't notice the return to neutral in VR if its gentle as your eyes convince your brain that you are still banked.

Hardware
It turns out a lot of my ♥♥♥♥♥♥♥ to do with gearing slack and gritty movement were due to shipping damage which my platform experienced when I first received it. All the bits were there so I thought all was fine, but the motors/levers were jolted a bit too much. DOF Reality paid the return postage for me to send it back and they returned it much improved. Nice smooth movements without slack. Its not quite smooth as butter but then this is a $999 platform not something made by Boeing. The only remaining niggle I had (which apparently no-one else has raised with the suppliers) was an odd alignment thing whereby the SimTools software would say that the motors should only be at say 50% but in reality mine had moved 100%. In other words they were reaching max displacement twice as quick as they should. If anyone else gets this problem the suppliers now have a fix.

So where does this leave me now? Having a lot of fun and very happy with my purchase decision, but I must confess to being hooked and wanting more. I'm now looking to do a DIY project of my own and build a G-Seat which is able to give persistent sensations of g-force: being pressed into the seat on a turn and feeling the seat pushing into your back as you are thrust forward in a fast jet. Apparently the airforce[www.stirling-dynamics.com] use them a lot.

[RocketMonkey]

Glad to hear! Once you get used to it, there is no going back.

[timterimtimtim]

Hey Phil - thank's for your infos. I'm glad to read your thoughts about what to buy and what's worth it. I'm in the same situation now. Is there any update what you would suggest to buy?

I'm using P3D V4 and my biggest question (nobody can really answer) is: what about taxiways and runway-vibration or small movements from the wheels - can you feel these effects?

Or do I have to use a butt kicker for those effects anyway?

What would you recommend today for a constellation? FaseTech had some problems so they need more time to release their products.

Thank You!
Tim

[timterimtimtim]

@Fluke Do you have any updates? Are you happy with the 3DOF?

Originally posted by Fluke:

Great post. I am currently waiting for my 3 dof to arrive. I already have a rift and have been running various flight sims in my Obutto with a modified seat fitted with vibration motors. I am hoping the 3 dof will add more immersion and will be following the development of the add on 4th dof with great interest.

I believe Igor is working on a low cost 6 dof platform, but is some months away from a final design.

[Spit40]

Originally posted by timterimtimtim:

Hey Phil - thank's for your infos. I'm glad to read your thoughts about what to buy and what's worth it. I'm in the same situation now. Is there any update what you would suggest to buy?

I'm using P3D V4 and my biggest question (nobody can really answer) is: what about taxiways and runway-vibration or small movements from the wheels - can you feel these effects?

Or do I have to use a butt kicker for those effects anyway?

What would you recommend today for a constellation? FaseTech had some problems so they need more time to release their products.

Thank You!
Tim

Yes I'm on the mailing list for FaseTech. That thing keeps changing, getting bigger and looking more expensive every time I see it.

Right now I'm still not really using the 3DOF. The mechanical issues I had early on are sorted. It's now down to the SimTools software. I'm fairly sure there's a bug in the filter settings that presumably doesn't get noticed by the car drivers but matters for flying. With a platform that can only tilt/pitch/rotate by 10 degrees or so you rely on 'motion cues'. This is where the initial movement (the acceleration) is actioned by the platform, but once you settle at the new angle the platform slowly and imperceptibly levels off and the mind/eyes take over to convince you (which they do very well). This slow imperceptible thing is done by the washout filter and that's what is buggy. I've sent data to the developer to demonstrate the problem and he tells me he's working on it.

The other thing I've had trouble with is motion cancellation. You need to run in SteamVR and use an unmaintained 3rd party app to avoid your head moving in the cockpit when the platform moves. It was very unreliable for me, but since I relocated my buttkicker it's been better. The vibrations seemed to confuse the tracker - still it does cost me FPS to run in SteamVR, as I'm on Oculus. My 1080ti can't quite handle ultra everything and SteamVR.

As for runway vibrations these are more a job for a buttkicker, but you need something like SimVibe for the best experience rather than just bass frequencies from the normal game sound. SimVibe doesn't support FS2, but the SimTools people are about to release GameVibe which does the same job and I expect that will support FS2.

Right now, due to the filter and motion compensation issues I'm working on a G-Seat. This is what G-Seats are all about:

https://youtu.be/K1xlHlnU-hE

Below is my project. I'm trying to do it the simplest way possible, with the fewest components, rather than some over engineered victorian steam engine type thing. If anyone is interested, when I perfect it, I'll tidy up the design and document the build steps more clearly. Costwise it should come in at around £250.

https://www.xsimulator.net/community/threads/g-seat-ultra-compact-servo-based-part-1.10470

[timterimtimtim]

Okay - now installed my ButtKicker and found a software for P3D (OpusFSI) which controls runway, taxi & turbulence vibration. That really impressed me - so thanks for the BK-Tip.

The FaseTech - well, I checked their products. The new release looks great - modern and professional with black. But the inside looks the same as before: https://www.youtube.com/watch?v=bLQM-arAxdg SO - I can't see the price really. Is it better than DOFreality? Because of what - stronger motor? Even Software is the same. So I was wondering, why they sold a basic DOF-system for much more money.

Then I talked with Igor from DOFreality and he told me he's working on a 6-DOF-platform for professional flight simulation. That guy should cost around 4000$ - they aim to release around x-mas. But he asked me why I need 6 DOF - and I told him for flight simulation. His opinion is 3DOF is OK and will do its thing.
I'm flying just Airbus & Boeing aircrafts - and their motion is not that big, right? So I think a 3-DOF and (maybe) a second BK will really do it - what do you think?

4K $ is quite much - and there is another point: I don't have that much space in my room. Because it's also my office - and I have to move drums & piano to the livingroom (I'm prepared for discussion with the girlfriend). So all in all I think about 3DOF. 6DOF will need more space - also height.

But there is one thing - I really want to know, but can't test it: Can I program the SimTools, that while doing TakeOf the 3DOF-System will move UP and DOWN like this:

https://youtu.be/j9p5AORcY8o?t=12m11s (look at 12:11)

Do you have kind of metric dimension of this 3DOF-thing?

Thanks for your G-seat-link. I'm very interested how it goes on!
Tim

[timterimtimtim]

EDIT: Everyday there is a new thing you get to know about motion platforms :-) I retract my critical opinion against the Fasetech-construction. Because I saw, that DOFreality (2DOF with rotation-motor) is fixed with a center joint under the seat. THAT means, you can't really move UP and DOWN with heave, which you really should for TakeOff or flying in turbulences, right?

So I ordered a DOFreality 3DOF and refund it today by noticing the center joint - really now thinking about a DIY, or buying the FaceTech, when it's released - take a look at its heavenly heave:

https://youtu.be/VvBojB_RUBA?t=5s