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View Full Version : What is FFB Clipping?



Helmethead1031
15-06-2015, 01:41
Excuse my stupidity, but what exactly is FFB clipping? I've read multiple threads that refer to it. I also thought I read somewhere you can see if your wheel is "clipping" in the telementry. Sorry if this has been previously answered.....I did search before posting.

jason
15-06-2015, 01:49
http://www.racedepartment.com/threads/like-your-ffb-strong-think-again.30763/


Niels_at_home




Reiza Studios




Heyas,

I've been around this simracing scene now forever and it seems the vast majority of folks like to run very high force feedback settings. Then you often read claims how great it feels and how they can even feel the effect of flies building up on the windscreen through these FFB settings (sarcasm = on). Some even feel when the coffee is done in the kitchen (sarcasm = still on)..

Force Feedback talk
Good sims will use complex physics engines to calculate the force feedback. Part of the feel is the tires, part is the suspension geometry, and this all changes with steering angle and things like how much weight (load) is on the tires.

If you'd only feel the tire part of the force feedback, the forces would be near ZERO by the time you've applied the optimum steering angle to get maximum grip. Thats just how tire physics (pneumatic trail) works, give or take some margins. Counter intuitive eh, but its often near true!

Suspension geometry usually adds a chunk of force, but still it is higly likely that the force you feel in a racing car drops off after a certain amount of steering and by the time you've applied the optimum steering angle for max grip, force through the steering wheel might be about half of the maximum.

That means when the steering goes light in a racing car, you might not be understeering at all, you might be right at the maximum grip levels!

Problems with sims
Even when your favourite sim has good tire and suspension physics, that doesn't mean your wheel (G25, Fanatec, Thrustmaster etc) will behave properly. The physics engine will just calculate a torque or a steering rack force, perhaps during a lap this value is between 0 and 5000 Newtons.

At some point the sim will have to tell your FFB steering wheel what force it has to apply. You can imagine there is some scaling required. Ideally the 0 .. 5000Newton that occur on the track should be the range where your FFB wheel responds between 0% and 100% of its capable force.

This scaling is NOT DONE AUTOMATICALLY by iracing / LFS / rFactor&Realfeel !! You have to scale this yourself. In iRacing and LFS its the force feedback strength in the menu, with rFactor&Realfeel there is the realfeelplugin.ini 'Max Force' entry to adjust.

When you scale the forces down too much, you get weak force feedback. When you don't scale them down enough, you're asking more from your wheel than it can do, so at some point the forces will be trimmed. This is called 'clipping'. If your wheel has a maximum of 100, you can't make it do 200. So anything you ask from it above 100, you won't feel a difference.

First chart: Scaling the force feedback

[​IMG]
The blue line is how a good simulator might calculate the force feedback strength versus your steering wheel angle. It is what it *wants* your FFB wheel to do.

Lets say proper scaling means you have to run the ingame FFB strength at 20% which is not uncommon at all. In this example, 20% strength matches the maximum occuring force feedback of the physics engine to the maximum feedback your wheel can put out.

If you'd use 100% ingame FFB strength, you would only have a small part of the desired curve fit below that line. That is bad.


Second chart: Results
[​IMG]

This chart is the results; what YOU feel on your wheel. You can see that running 100% FFB strength tries to make your wheel 5x stronger than it really is. It just can't do it, so you feel the red line. Apply steering, forces max out *very* quickly, and as you steer more, the force stays maxed out. It hasn't got the power to follow the desired dotted line. This is what many simracers do probably without knowing it. The force feedback isn't detailed at all, its almost on/off.

The green line is what you get with proper scaling. It follows the desired shape exactly, but now with the maximum occuring force nicely matched to your wheels maximum deliverable force.

Now why does 100% still feel stronger than 20%, despite the maximum force being the same? At 100% you have to grip the wheel like mad because any slight bump or minimal steering will result in maximum force. Once you're steering, the forces are mostly constant, but going near straight you feel strong jolts left/right as micro bumps / steering inputs cause these forces. Wheels setup like this are often unstable and will oscillate when you let go of the wheel on the straight. For some reason lots of folks think this feels good.

So how do I set this up correctly then?
Thats the hard part. Even on the same car if you change the car setup (caster, downforce) the numbers will change. On a flat street circuit the values will be different than in a fast banked oval.

Realfeel with rFactor is the easiest, you can drive the car on a track, look at the telemetry, and the 'Steering Arm Force' that you see in a hard corner is your desired Realfeel.ini "MaxForce" entry. Don't look at short spikes of force, go for a sort of average force you see in a fast bend.

With other sims its a matter of getting a feel for what your wheel can do. Once you know what its maximum strength feels like, lower the ingame FFB strength until you clearly are below this maximum force. Then add force slowly until you get to the point where it seems saturation occurs. I can't help much, the FFB strength will typically be between 1% and 100% :S. Try the maximum force in a steady corner, because on a straight, the sudden left/right jolts of too strong force feedback will make it feel subjectively stronger than it is.

Conclusions?
Current wheels like the G27 are fairly weak; they can't really deliver a strong force. It is very easy to try and ask too much from the wheel. It might also lead to overheating and faster wear!

I've tried to show you what force feedback scaling does and how running too strong force feedback settings can numb down the detail you feel, even when it *seems* like the effects are nice and strong.

Everybody is free of course to use whatever setting they like, but at least this shows that people running very high FFB strengths claiming they get lots of detail and a good feel for the car, are wrong from an objective point of view.

Helmethead1031
15-06-2015, 02:25
Thanks for the quick reply......my head just exploded! :)

clean as i cwn
08-10-2017, 08:45
Lol my head too could you please convert all this into thick man terms

John Hargreaves
08-10-2017, 15:27
Put the gain at 100%, scroll through the telemetry until the FFB graph appears, then adjust the volume until the graph line hits the top but doesn't get cut off. You then have maximum FFB without losing any detail.

Clipping is shown when the line on that graph gets cut off and goes flat. A little bit of this is ok, just on the really big FFB forces, but too much and the FFB just feels heavy and mushy.

Also experiment with tone and FX until it feels good. Some cars and/or tracks benefit from a bit of tweaking but it's a bit of a personal preference thing past a certain point.