DCS: speed perception, world scale, scaling at distance

So yes, after having DCS installed on my rig for a couple of years now during which I was buying modules but not really flying them :grin: I finally fired it up…
…boy is it cool! :+1: Especially in my Reverb :vr:

I am messing around just with the F-15 (yeah I know, don’t laugh at me :rofl:; I am sure I will progress to full fidelity modules one day!) and have a blast (still trying to figure out why I get a R-60 into my face from a MiG 23 dead ahead which is not picked by my radar but OK… there we go, I am still learning).

Now my question to you - more seasoned DCS pilots:

I got a bit surprised how easy it was to slip into formation with other F-15 and keep it. When trying again and again, I realized that even though my closing speed was about 50-60kts (so around 100kmh) the impression I got was approaching the other F-15 at rather a (very) slow speed :thinking:

I got a similar feeling when approaching the filed at some 180kts. When looking to the side and down it felt like flying in a C172 and approaching at roughly half the speed.

I know this has been discussed already but what is the general conclusion on this issue? ED claims on its forum that all is OK if I am not mistaken. Is there an issue with world scaling or perhaps scaling of models in distance? I mean… when in real life I am standing next to a road and get a truck passing by at speed of 100kmh the sensation of that truck approaching has nothing to see with the F-15 approaching another F-15 at approximately the same closing speed.

What is your feeling towards this issue?



PS: The force IPD in DCS is unchecked and I am aware of FOV (and lack of peripheral vision on my Reverb) and its impact on speed perception. However, that should not be an issue for me since the FOV is set spot on for my Reverb and the plane I am approaching is ahead of me.

Can’t say I’ve noticed any problems with this.
Of course judging speed at a distance is hard. Looking at an object far away makes it seem slower, that one passing nearby. Same with large objects.

I have never tried it myself, but is it possible to run DCS in slow motion? I know I made this error in IL-2, where I thought the 262 was very docile and slow. Turned out I was running the sim in slower speed…


Hmpf, sniped by Troll. Anyway, here is my opinion on the matter:

I tend to say that everything is OK.
However, there are several factors influencing that.

The sensation of speed is very different when you are not very close to the ground. You lack the reference points to the surroundings, that makes it different (it feels slower).

A 100kmh / 60knots speed difference between planes isn’t a lot when you have a mile or so to adjust for it. The distance is the key here.
In your excellent real life example the speed difference between you and the truck is the same 100kmh, but on a way shorter distance. If you watch cars going by at 100kmh, but from a mile away, then they look not so fast.
That’s sadly the reason why people die trying to cross motorways. The cars look not very fast from afar and you only have to cross, like, 12 meters of street. What could possibly happen?
Once they come closer you realize how fast they are.

The other point about that is the direction. If you are looking exactly into the same direction you and the target are moving, then you have no change of angles, the target just gets bigger. Humans are way less precise in judging size than they are in judging angles.
In traffic you can see that phenomenon as well, and it is known to cause highway accidents. The cars directly in front of you (like when approaching a traffic jam) may be 100kmh slower than you and you will notice that surprisingly late if you don’t pay attention properly.

In 2D it is harder than in real life.
In VR it is easier than in 2D (still not like in RL but closer) and makes rendezvous with other planes (like tankers or in your formation flying example) in DCS a lot easier.

If you start out at 60knots speed difference a mile (or even half a mile) away it is relatively easy to adjust that speed. If you had the same speed difference in a car at that distance it would be as easy.
When I drive 100kmh on a normal, straight road and there are traffic lights ~300m (one fifth of a mile) ahead of me that turn red (that happens on my way to work daily) I have no problems at all slowing down to 0 in my car and hit the point to stop precisely.


If you really want the sense of speed, you need panic!

I must also note that 60kn is not 60mph, but closer to 70mph (110kmh) and that ~15% counts!

The statute mile is 5280 feet, the nautical mile is about 6076 feet.

Aginor has all the points pretty much nailed down.

This is even quite apparent in cars - driving on the highway at 100km/h to 120km/h in my small Ford Fiesta feels much faster than in my dad’s GMC Acadia, which comes down to that small ride height differential. For me, moving from 100 to 120 is noticeable. In the Acadia, which I have driven from time to time it’s much less so (as such my Dad has got speeding tickets by incidentally creeping up in speed without noticing). This is car scale - a cockpit on a fighter is already even higher riding, even on the ground.

I once read that Humans are very much contrast based for our sense of sight. So that slow apparent size change from tail-on is very gradual - low contrast, until you are very close (relatively). The street crossing example is good at showing how you won’t catch on until the contrast (angular difference over time) increases with the vehicle being closer.


It is also way harder in the air since generally you don’t have the “banana for scale” items surrounding you. When you are driving you have all those 3D objects all around you that you are familiar with whizzing by, helping you judge your pace and place in space. In the sky, you don’t really have those inputs. Clouds don’t help…and scenery below generally doesn’t help. So you have one object (the other plane) that is where most of your data is being derived from.


One of my most evil fantasies is to build a banana model that is 50% larger or smaller than a normal banana but looking the same otherwise, and then include it in a lot of pictures. :smiley:


Make it more evil - 3d print a dozen of varying sizes (since it’s easy to scale) that are overall largest/smallest 50% larger and use them at random.


I’ve never done formation in a jet. But I have done a bunch in small planes where the initial closure is more like 30 knots or less. DCS seems spot on at those same relative speeds.


We are talking about size perception here…but given it is @BeachAV8R, I’m going to assume that this is not a phallic innuendo…

So, what is the “banana for scale” factor? :slightly_smiling_face:

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We ending up in another banana measuring contest? Tsk gsk, pilots :roll_eyes:


Thanks…an entirely new part of our modern culture that I never knew…and wish I still didn’t. :grimacing:

For reference, IMHO, a dollar bill (or any currency bill) is better since all of standard size… but that is just me.

This post is this big:

Or maybe this big…

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Einstein had stuff on this. To me however, in DCS, VR, the sense of speed isn’t as good as it used to be many versions back. I think it’s cuzz the trees are too big (and yeah, that topic really gets some peoples gyro’s spinning on the DCS forums).

I tried to mod it with no success. I seem to spend most of my time in the NTTR map. Last night I spent some time in the Persian Gulf map and the ‘clutter’ where I was flying had smaller trees/bushes/whatever it’s called, and it felt like I was going faster. Wish there was an option to scale these specific items.

There is a mod out that lets u change the resolution of the noise map. When I doubled it I seemed to feel faster on the deck; 500 knots felt closer to 500 knots, instead of 1/2 that. Haven’t reinstalled it on 2.5.6…lemme see what it’s called again…standby…


Seems that thread has sparked an interest from ED…
“Hey all, I asked ED to look at the adjustments made in the terrainoptions41.lua to see if atleast those could be used in some way, they will need to go through testing internally though to see how it performs on low-end machines, so we will see.” - NineLine

Well, it’s raining here so no golf. So I’m gonna put my geek hat on and try it again in 2.5.6. Thought about doing a video but I think it’s something you have to see ‘in the wild’.


I know…at first I thought I could see Blue Shift and Red Shift on fighters as they were coming towards me or away from me, respectfully. But then I discovered I had labels set to ON… :open_mouth: :wink:


Ah, happened to me with SAMs.
I was wondering why that little smoking dot was actually getting bigger… and then it hit me.



An hour later (is it taboo to reply to yourself?)

Ok, it worked on 2.5.6 – my computer didn’t explode.

This is one of those things you have to see for yourself; doesn’t translate too well in a captured 2D video so much, at least compared to VR. But, it does look sharper.

Assuming the params in the affected files do what I think they do, it should. And it does give me a better sense of speed down low, which me like .

I want to say it drops about 2 FPS for me but not real sure about that. This is all a S.W.A.G. It does appear, on my rig, to get about a 100 ms stutter every so often but by the time my brain goes, “hey”, it’s over and I keep going :slight_smile:

And since that one config file applies to both PG and NTTR it seems to help in NTTR. Haven’t tried the B-Sea map.

BTW, I have an i-6700k at 4.5ghz, nVidia 1080 8 gb, 32 gb RAM. So it’s not a top-of-the-line system…anymore :unamused: But neither am I…

Smooth rides, and check six

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It maybe something else. Your brain got used to “it”. To explain that here’s an example…
During pilot training in T-6 phase, initially I felt constantly behind the jet when in the pattern. Everything felt too fast. Few months later during end of T-6 phase, I felt that pattern…especially “speed” was sooo slow. It felt like everything was going in slow motion…

So…it maybe that you got used to the speed. Got ahead of your jet.
My 2c



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Wait till you progress to helicopters and your down low. Speed is very apparent then when dodging trees or buildings. I do however think you get a better perception of speed in Il2 BOS and I think that is one of the reasons dogfighting is more intense at least for me in il2 vDCS


A lot of the sense of speed comes from the FOV.
The narrower the FOV is, the slower your apparent speed is and vice versa.

There was a fantastic video of that taken from a train engine…