OT.. well on LFS :O)

That huge post of Todd.. About the feel of 'break away' being more related to the stop of force buildup and not a curve that drops.. Can I apply this to LFS for a moment?

There have been acceleration and braking tests in LFS and it was very hard to do better than a 'complete wheelspin' start or a 'locked tyres' stop. This might indicate, ever so perhaps, that the rise of the curves in LFS is on the steep side? I know the curves don't drop much in LFS, which is probably the main reason that its the best sim 'once it goes wrong' but the buildup seems very quick. Its easy to go from no wheelspin to loads of wheelspin in an instant, and in a turn, the difference between going through it smoothly and leaving skid marks is tiny.

Any thoughts on this?

I am watching that video daily and yes it DOES appear he's using slicks! That explains the wheelspin in all gears.. Surprisingly controllable though even with wheelspin!

The time it must've taken!

This one took 15 years though :O :O :O

http://www.youtube.com/watch?v=l3NVJ4pEFuY

to be fair its not 'RC' (imagine crashing it.. )

Georg, I have to redo the tests with a different setting. As the graphs show, using VSYNC often gives slightly slower response compared to running at high framerates.

It seems that if you use a program like Rivatuner, setting the 'max render ahead' frames to 0, you'll get the best performance, but I only tried that with rFactor. I'm quite sure this will affect RBR and NKpro but not sure how much LFS, N2003 and GPL will be affected.

I almost lost a partition a while ago. DR was lost and I haven't searched / tried to download it yet.. It was interesting as I talked about lag with Eero; I was lucky to be driving it before it went 'public', and he adressed the lag. Curious to see if 'render ahead' settings still affect DR..

I have no time soon to redo all the tests I'm afraid, some 'real life stuff' needs to be prioritized..

Xbit labs has a good article on it now too. Jumping to page seven:

http://www.xbitlabs.com/articl ... lay/lcd-parameters_7.html

you see that a newish 8ms rated samsung has a 47ms delay. With Rfactor at 230fps and 0 frames 'ahead' rendered, I get consistent results of 40ms lag. This is of course for the input, joystick processing, USB, game, then out to monitor again.

So one thing seems for sure, TFT lag is a factor, but new TFT's aren't nescessarily better than old ones in this respect.

Edit: and of course, any TFT running at 60hz will *start* the frame change after 1/60th second, disregarding 'other delays'. The pixel transitions will just be slower. Considering that many 'fast' TFT screens only reach their rated speed in certain situations like:

http://www.xbitlabs.com/images/other/19inch-4/10gr2.png

for a samsung 940B rated at 8ms.

Now if anything this means, unless my Philips is specced honestly (it is too old to find measurments of) that my 30ms screen is probably a lot slower than 30ms, yet I do find repeatable results of between 2 and 3 camera frames with rfactor at 230fps, 0 render ahead.

Edit2: Its a good article imo on Xbit:

Quote :

I’ve also read forum posts saying that it was just impossible to play games on a new monitor due to the input lag, but this had a very simple explanation. The user had changed the resolution from 1280x1024 to 1680x1050 but hadn’t thought that his old graphics card wouldn’t be as fast in the higher resolution. So, be careful when reading Web forums! You can’t know the level of technical competence of people who are posting on them and you can’t say beforehand if things that seem obvious to you are as obvious to them.

The input lag problem is also aggravated by two things common of all people. First, many people are inclined to search for complex explanations of simple things. They prefer to think that a light dot in the sky is a “flying saucer” rather than an ordinary weather balloon or that the strange shadows in the NASA photographs of the Moon are proof that men have never landed there rather than are indicative of the unevenness of the moonscape. Any person who’s ever taken an interest in the activities of UFO researchers and other folks of that kind will tell you that most of their alleged discoveries are the result of thinking out excessively complex theories instead just looking for simple, earthly explanations of phenomena.

Thankfully the 'techy' threads on the LFS forum about physics etc are proof that there is a lot of sanity as well but sometimes when I'm looking at overclock / pc hardware forums I don't know if I should laugh or cry..

Last edited by Niels Heusinkveld, Wed, 24 Jan 2007 10:02. Reason : more ramblings :)

Reading your first post gives me the impression that you're a rarity.. Working brains! Thats only witnessed by about 10% of teenagers! The ability to write is even rarer..

You're a few years ahead in some ways. I sort of had the same thing though at a later age (~18..19). I didn't fit in well with the first year uni students but made some good friends who where a few years older. I got far more socially adept but still I couldn't keep a conversation going with the average first year student. It can be tricky as the majority goes for 'quantity' (many parties, booze, shaggin around) and it sometimes seems that people don't have personalities.

Only much later, when I was about 24 did things change a bit and since then I match better with most people of my age. I do notice that I lack that sex/drugs/rock&roll teenage experience even today but at least I find that once people get in their mid twenties they actually come out with personalities that they've always had, probably, but kept hidden while living the 'standard' teenage life.

I think its a balance thing. If life is one big spring break party its no good but if you're too distant from those things it can hamper your social life, and social life is very important for us human creatures.

I finally found the full lap Montreal in the Wet, 1978. Depailler, thank you!

http://www.youtube.com/watch?v=KwVIa6vA4x4

It might just be me but I only had the last minute in lower quality.

Definitely worth getting the video using www.keepvid.com as fullscreen playing over VLC is smoother and uses 75% less CPU than fullscreen Youtube !

Speed drifting is a bit like speed walking (the olympic 'sport')

"Ok guys, this is the fastest way around most turns, but you may NOT do that!" errrr

That is an interesting question. One way you could say that when GPL runs 'maxed out' (i.e. 36fps with a bit of headroom) that I can't imagine that things like USB joystick 'transfers' are slower on a p3 450mhz. But that might be a wrong assumption..

I could use the TVout Shotglass but I doubt that such a 50hz monster is a good idea? Plus its not the absolute lag that I'm after, its more the relative lag between sims, and really I am quite sure the measurments are 'acceptable'. There is a consistent difference measurable between 0 render ahead, 2, 4 and 8.. Small differences show consistently.

There is another thing that puzzles me though. As mentioned and probably possible (I don't understand the inner workings of sims, physics / graphics loops etc ) is what's been said about the lag just being a visual thing. What I would think is the whole sim is a 'loop'.. sure the physics are done at a higher rate than the graphics but surely the lag measured as I did means you can't SEE what happens and the RESULT of the inputs some 0.xx seconds later. Then illepall that is exactly the same as delayed inputs. The only condition I can think off is indeed that the game doesn't use smoothing filters on the graphical wheel which could make it laggy. If there is no smoothing there, any visible delay IS "sim lag" (if not inputlag) that simply puts some time between what you do and what you see. So imo, whatever causes this and whereever it goes 'wrong', I don't see the difference. Lag = lag surely? I mean even if the physics react to the input after 0.000001 seconds, if I don't see it after 0.15, what's the difference?

Edit: Hyperactive, I do have a high-end USB controller chip, probably much more advanced than those used in the expensive wheels. My gut feeling is that there is likely to be not much of a difference and the main lag comes after the controller so to speak. It is dangerous to make assumptions though like I do now though

Last edited by Niels Heusinkveld, Tue, 23 Jan 2007 10:29.

Good nose and bad nose..

Changing the pre render limit down to 0 does have a pretty positive effect on Rfactor. Tripple buffering showed a 0.01 second improvement at high framerate and a 0.01 second loss at low framerate, i.e. that is clearly no difference at all..

The bad news is I have to re-test everything now with max prerender set to 0

I already had that RBR 'tweak' done btw, except removing that constant force multiplier line but I think that is of no use when not using FF anyway.

It will be interesting to see the effect of this: Will it make all sims 'quicker' or only the slow ones? Stay tuned... :o

I hope to test 'render ahead limit' of 0 and 5, as well as tripple buffering on / off tonight, although it went on til 5am last night so I might choose the bed for some good 8 hours of 'lag'.

I don't know about a fix like that? An URL is appreciated.

My feeling says that the 'frames rendered ahead' and 'tripple' buffer thing as often mentioned as a cure for lag is something that begs to be tested as well..

Again, this whole thing gave consistent results, it is not about absolute lag but lag comparing various sims on the same hardware running at various fps.

Btw, 0.05 seconds is very very fast, I can't witness it as visible lag I must say LFS with Vsync (so 0.1s) is still 'fast' and definitely not witnessed as a 'considerable lag'. It only clearly visible above that. That is mainly the reason why I did this test; it is hard to 'see' the difference as the more a wheel turns (like 720 in lfs) the faster it seems to turn etc.. This camera test is a fairly objective judgement.

It is pretty hard to do with wheels as you want to test the analog axis (not a button) and you'd need a 'step' response, i.e. considerable turning in an instant. I'd have to disconnect the potentiometer and connect another 'rig' that turns it very quickly.

It could be that some games do a filter for the graphical wheel however I used to have a very jittery gameport wheel which would make all sims except GP4 jitter. If the graphical wheel copies the jitter of the wheel, there is probably no filtering done. I don't know about Nkpro in this regard btw..

since monitor and input device where constant, this makes the results comparable. They might not be 'absolute' but can be compared relative to eachother.

The differences where very small and the results very consistent. I am quite sure that any trends that came up reflect actual situations. Until I read something that convinces me of the opposite..

Hi guys,

What did he do this time?
I made a pretty thorough analysis of input lag in the following sims:
- GPL
- LFS
- N2003
- Nkpro
- RBR
- Rfactor

How?
Using my Canon S3 IS digital camera to record, at the same time, the monitor image and a small joystick on a gamepad, engaged with a 'ghetto' spring loaded device. So I am recording the input (joystick) and the response (monitor) at 60 frames per second. I count the amount of frames it takes for the monitor image to respond to the joystick. I do this five times for each sim (at various framerates) and take the average.

Here is the 'plan' in a picture:


How accurate?
It is not highly academic. The monitor is a TFT running at 60Hz. So even with games running at 200fps, the monitor won't show all 200. Furthermore there will be some delay before the monitor responses. The camera at 60fps will probably not be in perfect sync with the TFT monitor. Still, roughly 1/60th of a second is a good accuracy and the results where consistent and there was enough difference between the sims and settings to give some interesting results!

What settings?
Various frame rate ranges (after tweaking graphics / underclocking PC to get the result within the range):
- Low framerates between 27 and 37
- Good framerates between 54 and 61fps
- Very high framerates between 90 and 140
- Insane framerates of about 230

System:
- AMD64 at 2.5ghz (3800+ abouts) underclocked for some of the low fps settings
- Nvidia GF6800GT 256MB Driver version 84.26, with AA / AF to reach target fps at times
- 1GB ddr at ~225mhz
- Windows XP sp2, full updates
- no 'usb overclocking' (standard 125hz speed. Can't yet be arsed to test this)
- Philips 20'' TFT rated at 30ms for what its worth
- Thrustmaster dual analog gamepad



Also:
- VSYNC on, 60 frames per second
- In LFS and NKpro, setting a max framerate in game (37Nkpro, 30 and 18 LFS)

Results
Compiled in Excel, the absolute delay (in seconds) versus the framerates, not limited by game limits or VSYNC are:


The relative lag, measured in simulation frames is:


How in game framerate limits (cap) and VSYNC affect the absolute input lag:


Conclusions
When not using VSYNC or in game frame rate limits, looking at the absolute lag:
- GPL makes a good show: The least amount of lag at the lowest framerate
- LFS is the best of the rest although it needs more than 100fps to get to GPL levels of response
- Rfactor is affected the most: at 27fps the lag is almost 0.25 seconds!
- RBR and NKpro aren't much better with terrible lag at lower framerates
- RBR and Rfactor need 200fps to be on a par with LFS at 100fps

When looking at how many of simulation frames the lag is:
- RFactor and RBR displays a linear ratio: double the framerate, halfs the input lag
- NKpro is unaffected, the lag is almost constant regardless of FPS
- LFS and N2003 do relatively better when the framerate is low
- GPL makes a great show again: it takes less frames AND it happens at a higher framerate (both have a positive influence on lag) to respond.

When using VSYNC or in game framerate caps:
- Vsync results are very close, between 0.1 and 0.115 seconds, except for GPL which is probably not working well with vsync as 60hz monitors and 36fps might not match..
- Framerate caps as selectable in LFS and NKpro work well
- NKpro 37fps, at 0.08 seconds is almost 2.5 times faster than when system performance limites the framerate at 37, with a whopping 0.19 seconds delay!
- LFS with a 30fps framerate cap comes in at close to 2.5 times less lag than running 'system limited' at 28fps.

Other things that struck me:
I have also looked at the number of video frames it took for the steering wheel to go from center to max lock. This was pretty constant at 3..4 video frames (making that 3.5 gives 3.5/60 = 0.058 seconds) Only N2003 was slightly slower at 4..5 frames.

In N2003 I seem to feel more lag than the numbers show. I do have a possible explanation. With all the other sims, as soon as the steering wheel moved, it showed a fair amount of movement. With N2003, very often, the first video frame showing wheel movement only showed very little movement. This seems to indicate that N2003 does not havea totally linear 'response speed'; as if there is some speed buildup.

What do I think?
Input lag is a bad thing. However, even you don't or barely see it, it is still there. The quicker a sim responds to your inputs, the more direct control you have over the car. In my opinion, there is NO reason that new games shouldn't be able to deliver the same quick response as GPL; a game from 1998!

I don't want to go deeply into a "when is it good enough?" debate. If technically a lag of 0.05 seconds is possible with a sim running at just 36fps, then this is the benchmark. A sim maker has no excuse when his sim has more lag at lower framerates. Anything has to be done to make simracing as 'immediate' as possible and reducing input lag should be very hign on the list.

Meanwhile, VSYNC doesn't help, which is sad as that looks so much nicer on TFT screens. It is obvious that, especially with Rfactor, RBR and NKpro, you are much better off sacrificing detail for speed.
Isn't it dubious that an 8 year old sim basically wins this? I can't call it a victory for RBR / Rfactor as they need to run at 6 times the framerate to beat GPL.. LFS is the best of the rest, especially at lower framerates.

Food for thought, and for the sim Devs out there! (hopefully)
Hope you enjoyed this

Niels

Last edited by Niels Heusinkveld, Mon, 22 Jan 2007 13:24. Reason : Added system specs and edited reason for editing :)

The good thing about not having a complete Xj220 is that there is no radio.. So it can't fall out of its 'socket' when accelerating (as Clarkson managed)

True.. In a good sim (shame the 79 mod runs on ISI physics) though, I would have fun

"Dear sorry tyres!" Tiff in the Z06 (wrong aspect ratio but still..)

http://www.youtube.com/watch?v=G9bByWD4Oxs

And, while great to watch, almost never do you get a 'fast' lap, let alone a 'mad qualifying' lap. I find the wet laps the most fun, Cheever at Detroit, Depailler at Montreal: laps where they really had some fun.

http://www.youtube.com/watch?v=s7Jm4jNUjzs < Cheever! Wheelspin, opposite lock, gimme that car and track combo with good physics and life is complete..

And when they DO floor it in those vids.. oh my!

Hi lads,

Would this work? I have one XP Pro license, but I would like a dual boot. Why:

- My 6800GT soft mods into a Quadro card, great for CAD
- My SBlive needs custom drivers for audio / music software, which doesn't work well with all games..

So having two installs would stop me from having to reinstall drivers all the time.

Technically I don't see a difference as XP is still installed on ONE machine and running (of course) on ONE machine at the time.

So can this be done or will MS send a SWAT team to my door?


Niels

Quote :

I have AA/AF on high and I get 70fps on a full grid.

So should we worship you now?

I call it "not being very good at it" I'm going to invest in something like racing shoes. Socks + 20kg brake force = not comfortable for long periods.

And about the telemetry, even if that is available, the longitudinal G force will also be affected by brake temperature, engine braking etc so when the relationship between pedal pressure and G force isn't 1:1 we'd still not know for sure what causes it.

oh the porn!

http://www.youtube.com/watch?v=hg7LDUMmB1A

Thanks JB, good post.. Basically then it is not up to the hardware (pedals) to cause this effect but it should be in the sim, as each car might be different. But we still have no numbers.

I'll gladly believe that I'm just 'crap' at heel & toe but surely not everybody who does it for real can be so crap at it that it hinders their braking?

I have seen some simmers videos where they don't heel & toe but just press both pedals at the same time.. Sure you can keep a constant brake force but its sooooo hard to keep 20kg on the pedal, move or tilt the side / heel of the foot and roll / press the accelerator. That probably gives me at least a 5kg 'wobble'.

Edit: the father of a friend of mine races and I saw he used MOTEC.. G sensors definitely, and perhaps brake system pressure.. I'll ask if he can have a look! Its an old group C car, dunno if he heel & toes but there is a good chance..

Last edited by Niels Heusinkveld, Tue, 16 Jan 2007 00:38.

It is 2007 and standards should be much higher than doing a half decent GP4 conversion imho. Then again NKpro should be a lot better than it is so perhaps that 'matches' :-)

LFS might only be dx7 but on most tracks things just look pretty good, not too saturated. Beyond acceptable and better than any 'shader using' sim (should say "sim") currently available.

Odd isn't it! I much rather look at LFS and even GPL than Nkpro / ISI dx9 stuff. I suppose the less there is, the less there is to f%#k up...

Yeah I was thinking.. Perhaps LFS does do quick changing surface temps but doesn't show it to us