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Force Feedback improvement - bumps feel through wheel
1
(39 posts, started )
Force Feedback improvement - bumps feel through wheel
I have always liked LFS force feedback, but after having tested for 1 month iRacing i have to say that imho lfs one is no more the best.

iRacing FF make the car feels much more realistic because it let the driver feels all the bumps located on track surface.
For the other things, it is pratically the same lfs FF one.

Feeling ALL the bumps increase a lot the "sense of driving a racing car", its feels quite "scary" at start, but it is a lot more fun after a bit of driving.

Actually lfs let feels only the biggest bumps on tracks, all the little ones are pratically uneffective on FF, even if can be clearly seen through suspension movements.

In my opinion lfs FF should let feel all the bumps like iR FF is actually doing

Driving LFS after iRacing seems like driving a car on a bowling pavement, it feels really flat. :/


P.S: i am using a G25, and i have used a DFP too, so it's not a problem with crappy steering wheels
#2 - ajp71
LFS FF is quite smoothed and I like it in a way. The problem with iRacing is I have to turn the FF strength down because the bumps were literally vibrating my wheel apart, between each 20 minute Legends race I was disassembling my wheel and tightening the screws on the back of my Frex boss to stop it falling apart.

If there was a way of getting mild bumps with otherwise stronger FF then I'd be all for it, maybe a separate fast and slow FF system than just smoothing the output.
in iR i used 20% force and it feels like 50% lfs force, but it had bumps too.

Try iR with 20
#4 - Juls
I noticed that IRL, I can feel bumps even if my wheel is centered.

Do not know where it comes from physically, but bumps do pull the wheel in one direction even on straight line where wheel is centered. It seems that when road is not symetric (for example a bump under left wheel and flat under right wheel) it has a strong effect on steering force.

In LFS you can almost not feel bumps when the wheel is close from center. Or bumps impact on steering force is too small to be noticed at 50% FFB. Or maybe tracks do not have enough bumps. There is something to improve there.

I suppose iRacing does not try to keep all the bumps in the track mesh. It seems to me track mesh is rather simple, and surface information is kept somewhere else....so that they can keep very detailed track normal map without needing a very detailed track mesh. It seems to me the best way to keep very detailed info from the laser scan without killing the framerate.
#5 - bbman
Quote from ajp71 :LFS FF is quite smoothed and I like it in a way.

I think that's down to the soft springs everyone is setting in LfS... Try to set a very stiff suspension in one of the cars (GTRs or OW maybe)... Then again, it could be that the graphical reaction to bumps may have just exaggerated the forces I actually felt through the wheel...

Quote from Juls :I noticed that IRL, I can feel bumps even if my wheel is centered.

Do not know where it comes from physically, but bumps do pull the wheel in one direction even on straight line where wheel is centered. It seems that when road is not symetric (for example a bump under left wheel and flat under right wheel) it has a strong effect on steering force.

Of course, that's down to the load of the tyre and its traction due to tyre load sensitivity...
#6 - Juls
Quote from bbman :
Of course, that's down to the load of the tyre and its traction due to tyre load sensitivity...

I do not think it is so easy. When steering wheel is centered and left tyre meets a bump while right tyre stays on flat surface, there is a stronger force applied to the left wheel. OK.

But remember steering wheel is centered...so tyre contact patch is almost centered too...and the force coming from the bump should not give a steering force because pneumatic trail and mechanical trail are aligned with the force and there is no torque resulting. It was stated here several times that you almost do not feel bumps in LFS when steering wheel is centered because forces applied on wheels give almost no resulting streering torque in such conditions. But from RL it seems something is missing...I can clearly feel bumps with my road car, soft tyres and soft springs, and sure it can not be explained by camber.

The steering force you feel on a bump when steering wheel is centered can only be explained if there is a rather strong change of the tyre contact patch shape on the bump.
Quote from Juls :I suppose iRacing does not try to keep all the bumps in the track mesh. It seems to me track mesh is rather simple, and surface information is kept somewhere else....so that they can keep very detailed track normal map without needing a very detailed track mesh. It seems to me the best way to keep very detailed info from the laser scan without killing the framerate.

This is the same in LFS. The displayed mesh has nothing to do with what we actually drive on. For example the curbs in LFS are rendered completely flat, but they obviously aren't when you drive over them. Or in some sand pits or grass areas you sink into the ground or in a few cases even drive above it.
Quote from Juls :...

To be honest, I'm not sure if pneumatic trail is even modelled in LFS, meaning I don't think the rubber actually twists while steering. I have no hard evidence for this, but to me it seems all forces come from camber and scrub radius. It's quite clear that the rubber bends due to tyre deformation, but that's probably only in lateral direction - so no longitudinal bending or rotational twisting.

Obviously it's hard to know for sure, since Scawen rarely talks about such details
#9 - Juls
Quote from AndroidXP :To be honest, I'm not sure if pneumatic trail is even modelled in LFS, meaning I don't think the rubber actually twists while steering. I have no hard evidence for this, but to me it seems all forces come from camber and scrub radius. It's quite clear that the rubber bends due to tyre deformation, but that's probably only in lateral direction - so no longitudinal bending or rotational twisting.

Obviously it's hard to know for sure, since Scawen rarely talks about such details

It would explain a lot if pneumatic trail is missing. I suppose tyre patch does not twist (or only at very low speed), but takes a trapezoid shape every time the track normal changes from vertical (on bumps or slopes), and is no more symetrical->steering torque.

I read somewhere nkPro was modeling pneumatic trail, and maybe that is why you can feel a lot more the bumps in nkPro.
Very well explained here: http://www.lfsforum.net/showthread.php?p=539489#post539489
Quote from Juls :I read somewhere nkPro was modeling pneumatic trail, and maybe that is why you can feel a lot more the bumps in nkPro.

My impression with the nKP demo is that they only use the pneumatic trail curve for FF generation, or a combination of camber induced forces with exaggerated pneumatic trail forces. The reason for this is because the force goes back to 0 (wheel goes limp), maybe even a bit negative when understeering, which is exactly how a pneumatic trail curve (self aligning torque curve) looks, which is however only a "small" part of the force that you should feel.
I'm happy to see that the thread has started an interesting discussion
Unluckily im not able to go so deep into details like you guys, but i hope devs will take a look there
#12 - Juls
In fact I can feel bumps in LFS too when the wheel is centered, but it is a bit weak when the FFB is at 50%. At 200% it is a lot better but then the self aligning torque is too strong for my wheel

I was thinking about something else...not only one should feel the bumps more, but bumps should have an impact on car trajectory and require correction.

In LFS when I take a strong bump only on one side (cutting a chicane), with the steering wheel centered, I can feel it a bit, but it does not seem the car trajectory changes. Or if the car trajectory changes it is too little, because I do not need to correct at all.

I do not have iRacing to test, but I suppose you feel bumps very strong and bumps change car trajectory too, and that's why users say they have to correct their line all the time. Is it right SpaceMarineITA ?
Juls: in comparison - LFS has NOTHING in the way of bumps compared to iRacing. It's a totally different style of driving actually, iR you need to correct for bumps pretty frequently into and out of corners, yet LFS it's for the most point turn in, apex, turn out, not much else.
#14 - Juls
Quote from dawesdust_12 :Juls: in comparison - LFS has NOTHING in the way of bumps compared to iRacing. It's a totally different style of driving actually, iR you need to correct for bumps pretty frequently into and out of corners, yet LFS it's for the most point turn in, apex, turn out, not much else.

Yes I understood that What would be interesting is to analyse what are exactly the differences, it may be interesting information.
LFS tracks lack bumps, and maybe this could be added easily (it seems the engine supports quite detailed road surface). But I suppose this is not the only difference.

I have a few questions for iRacers:
- when you are on a track with a strong slope, like an oval, and you keep your wheel centered...does the car follow a bit the slope or continues perfectly straight?

- when you are on a bumpy track, with your wheel centered, does your steering wheel move with the bumps?

- when you have one wheel on the track and the other on the concrete stuff they put inside/outside corners(forgot how to say in english), can you feel your steering wheel is pulling in one direction?
1) if I keep my wheel centered on an oval, it'll fight against me to turn left, and if I stay solid, I'll hit the wall, and depending on my velocity it will follow the trajectory of the oval a bit (not go directly off, but curve a bit). Higher velocity = less effect banking has = straighter trajectory into the wall.

2) centered steering wheel down Lime Rock Park - beautiful FFB of the bumps by agitating the wheel, but not enough for loss of control (while going straight atleast).

3) When you get 2 tyres on the kerbs (apex kerbing mostly), the car will pull to the kerb, along with the sound of the kerbing, and the bumps if you're going parallel to the kerb (while being on it).
Well, Dawes answered for me (dunno why im no more receiving mail notification from that topic o_O)

Like he said, in iR u have to care A LOT about bumps on track, it require pratically a completely different driving style.

However i dont think that lfs tracks are flat, i use Y axis head movements in lfs and sometimes even in straight these are really pronounced.

The problem is that even if the head is shaking a lot FF still feels flat

I know that patch Z is imminent (see Y31 thread) but i hope that at least in S2 final devs will improve that aspect.
Until now lfs had to care about sims of same year (ISI gmotor2 and pmotor2 are there since 2005, like S2), but now a FF "iR like" should really be the standard for 2008 and future years sims.
#17 - Juls
Only one person knows what is missing in LFS for the moment concerning bumps

What I can see, is that car trajectory is almost not changed in LFS when the car is on a banked road or receives lateral wind. And wheel is not pulling in such conditions.

I suppose this is somehow related to this lack of feel on bumps. Banking, lateral wind, bumps...all these things give some additional lateral forces on the tyre:
- on banked road the gravity is no more vertical (from driver point of view) and pulls laterally the car->suspension->tyre. Lateral wind does the same thing.
- when one wheel is on a bump, the road surface is no more flat under this wheel and pushes the wheel laterally.

It looks like in LFS tyres react "too well" to such lateral forces. They counter these lateral forces without needing any help, and as a result no steering torque is transmitted to the wheel, and car trajectory keeps almost straight and no correction is needed. IRL, such forces twist the tyre, and change the contact patch shape. As a result, you can feel a steering torque, and the car is not moving anymore in the same direction than rims, but slightly sideways. We all know how feels a strong lateral wind on a highway...

There are many bumps in SO tracks, my favorite ones. Very detailed road surface, with details like sewer...tramway rails. Maybe some more narrow bumps (affecting only one wheel) would be nice, but there is already everything needed to give a very good "bump experience" if FFB is updated.

I think new sims like iRacing are a very good thing...they push the envelope and force other sims to reach higher accuracy. I can bet next sims to be released will make a lot of efforts to better render bumps
#18 - Juls
I was wrong, wheel is pulling exactly as it should on banked tracks in LFS.
For example, the oval turn is banked 18 degrees, and the car receives 0.3 lateral G....the wheel pulls exactly as much as on the skid pad when you reach 0.3 lateral G.

LFS models FFB through caster (unlike ISI engine based sims) and that should be enough to feel very well the bumps. Maybe the problems comes when LFS engine has to estimate what lateral forces are caused by the bumps.

When I watch this vid, bumps give very strong lateral force (the bump in t1):
http://de.youtube.com/watch?v= ... _b&lang=deu&id=20

And this lateral force, through caster, should give far enough FFB. I really would like to know how LFS feels with a track covered with narrow, strong bumps like IRL.
one of the problems is that the virtual drivers arms are a very spongy and soft spring
it most noticeable when youre driving with a mouse in a car with strong steering torque... and i dont think the virtaul wheel movement that happens without your input has any effect on ffb
#20 - Juls
Every time I scroll down a thread, I see only your ugly avatars
This one is a bit less visible...but definitely the worst haha
Very intriguing to hear from the nKP front that the physics and FF have been massively improved in the latest 1.0.3 version so far. Can't wait to try that out, maybe the FF1600 feedback isn't as fake/off when over the limit then.

(Though it kinda puts the old physics/FF into perspective if a massive improvement was possible )
#22 - Juls
Yes, and he writes he got rid of Pacejka model. There are not too many ways to model a tyre in a PC sim. It's rather a Pacejka or a model which divides the tyre in several parts and check how these parts grip or slide or stretch...like LFS.

So maybe now nkPro has a very close tyre model from what LFS uses. At least in concept.
Well while playing I notice that if my wheel is at the straight ahead position, and I run over a curb, I'll feel that I've done just that.

However with the wheel even at 25 degrees either way, it will stop, it's quite awkward, especially under severe braking into corners.
#24 - Juls
Quote from S14 DRIFT :Well while playing I notice that if my wheel is at the straight ahead position, and I run over a curb, I'll feel that I've done just that.

I am still thinking again about it, and doing various experiments

I can clearly feel in LFS how the ground normal is changing below each tyre. When I run over a curb with the left wheel, the track normal is no more vertical under this wheel (assuming the car is horizontal). As a result, the tyre receives a lateral force, and I can feel this lateral force through caster and scrub radius. This is perfectly OK.
Similar thing when track is banked. The wheels receive lateral forces, and the steering wheel pulls.

But something is missing. When the tyre runs over a track irregularity like a bump, the wheel is losing a lot of energy and is braking because it is in fact like a little collision. And this is perfectly modelled visually in LFS, as we can see how the tyre deforms on a bump. This deformation shows that the bump is strongly braking the wheel, and we should feel this braking force through scrub radius. It should even turn the car slightly.
Scrub radius is modelled in LFS, tyre deformation too. But I do not feel at all the longitudinal braking force corresponding to this tyre deformation on track irregularities.
Problem is that almost all bumps are going over the whole stretch of the track, so you'll hit them with both wheels at the same time... And I've never felt longitudinal force through a wheel, neither in RL nor otherwise... That you'll only feel with your body...
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Force Feedback improvement - bumps feel through wheel
(39 posts, started )
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