FFB Guide
Input Signals
The four front tire input signals are the component parts of the whole tire induced torque coming
through the rack. So if these are all scaled to the same thing (by convention 1.0), this is the
same as straight rack torque.
The two rear tire signals are to enable the Seats of Pants concept. Neither of these go through
rack geometry though, as there is no rear rack and steering wheel. These just go straight to the
seat.
Finally, the G force signal is to enable the Gut physical simulation concept.
Tire Force
This is simply an overall multiplier on all of the input tire forces. Note that G forces, the input to Gut, are not
scaled with this parameter. Note that the other FFB parameter in the Controller section is the
same as the scaling in the driver. Reducing that does not help saturation, it simply reduces
force.
Spindle
SpindleMasterScale
This is a multiplier on all of the front tire forces. This was added to allow the following four scale
to default to 1, and be more intuitively like “weights”.
SpindleFxScale
SpindleFyScale
SpindleFzScale
SpindleMzScale
Individual scales on the components going through the spindle/rack. To get pure rack forces,
leave these all at the same value. 1.0 is a convenient value for this, and use SpindleMasterScale
to dial overall spindle force.
SpindleFxLoPass
SpindleFyLoPass
SpindleFzLoPass
SpindleMzLoPass
Individual smoothing on the components going through the spindle/rack. Typically Fx requires
more smoothing than the others. 0.0 is no smoothing. 1.0 is normalized to “really smooth but
still some useful signal”. Values above 1.0 are valid.
SpindleArm
SpindleArm is the angle, in degrees, of the attachment of the tie rod to the spindle. Zero degrees
means the tie rod is attached directly aft of the axis. That particular distance, how far aft, is not
critical, because that just amounts to scale, which we adjust based on squeezing into the device
range anyway. The angle though matters a lot in how the forces feel when the steering wheel is
not straight.
90 degrees is then with the tie rod directly inboard of the axis, which physically would result in the
inability to steer. Realistic values I'd guess are between 0 and 45..
Seat of Pants
The basic idea of “Seat of Pants” is to present information from what is happening at the rear of
the car through force feedback. There are two physical forces that are used. The rear side
loads and the rear vertical loads.
SoPScale
Overall scaling of Seat of Pants
SoPLateral
Scaling of the rear side load effect.
SoPDifferential
Scaling of the rear vertical load effect, which is actually the difference between right and left
vertical loads.
SoPLoPass
Smoothing of the Seat of Pants signal. 0.0 is no smoothing. 1.0 is normalized to “really smooth
but still some useful signal”. Values above 1.0 are valid.
Relative Torque Adjust
The idea here is to present torque to the wheel based
on the change in torque through time instead of as absolute torque. This means that with
reasonable parameters, the wheel will never fully saturate. But unlike soft clipping (which can
also prevent saturation), the high end torques do not get as heavily squeezed.
There is one side effect to tune out though, and that is the wheel losing center over time. If all
torque was completely via “Relative Torque Adjust”, centered torque would move around as the
wheel goes through previously saturating torques. To prevent this, we use the bleed value to
“bleed” absolute torque back into the mix.
RelativeGain
This is the scaling on the amount of calculated torque change that is applied. 1.0 is the intuitively
correct value. 0.0 turns this component off.
RelativeBleed
This is a time value for bleeding absolute torque back in. 1.0s is a good starting point.
RelativeClamp
This is the force to wheel value (so in the 0.0 to 1.0 range) where the non absolute running
magnitude is clamped. This does not clamp the overall value, and torques can still go above
this, but it does exert a strong clamping effect. 1.0 is a good starting point for this. Values
greater than 1.0 can make sense if soft clipping is also used. Values less than 1.0 makes sense
to give some headroom for spikes to be a little more symmetrical around the clamp.
Note that with this component on, and with clamp at 1.0 or less, and not too much bleed, there is
no full saturation. What this means is that what was too much force before now becomes more
force effects felt near full force. But this too can become too much, as that can start to
overpower the more subtle unsaturated force range. So you still need to dial overall force (via
Tire Force and the scales), but that scaling can become an interesting control, not just
something to avoid saturation with.
Gut Simulation
This is a simulation of the G forces on the body of the driver. Basically, G forces move the body
around via a physical simulation, and the result of that simulation is translated to force feedback.
GutScale
Magnitude of the gut simulation in FFB. 1.0 is normalized to “significant but not overpowering”.
GutLongScale
Magnitude of longitudinal effect applied. This is a scaling of the baseline lateral effect. At 0.0, the
gut effect will be all based on lateral G’s. With non zero GutLongScale, under braking G’s, the
lateral effect will increase, and under acceleration G’s the lateral effect will decrease.
GutMass
This is the mass of the simulated “gut”, which should not be the whole human body. It should be
some lesser portion, roughly being the effective amount of mass not “locked down” rigid by the
seat and seatbelts. This is a very fuzzy concept, so the number is really just a very rough
ballpark number. This is fine, because the simulation is not overly sensitive to this number. It
matters, but it is not extremely critical.
The default is 50 kg.
Arm Simulation
The arm simulation simulates that the wheel is driven by a non rigid linkage, namely the driver’s
arms, as well as play and mass in the linkages themselves.. However, this is done purely with
force feedback. The position of the the controller still directly dictates the location of the
simulation wheel.
This simulation also serves as the main global smoothing stage.
ArmScale
Ratio of incoming signal to pass through the arm simulation. 0.0 if off. 1.0 is application of all
incoming signal.
ArmMass
Mass of “arms”, with respect to simulation. This does not necessarily mean the average mass
of two human arms. This is the effective mass with respect to the degree of freedom that is the
wheel/controller.
ArmStiffness
Spring*like stiffness of the “arms”. Stiffer settings will pass through higher frequency
information. Softer settings will smooth more.
ArmDamping
This is a multiplier on critical damping of whatever mass and stiffness is set. Therefore, 1.0
means exactly critically damped.
Soft Clipping
This compresses all force within range of the wheel, although the stronger the force, the more it
is squeezed into the higher force range. In some ways this is like Log Scaling, but Soft Clipping
guarantees all signal will squeeze into the range, however compressed. On the other hand,
approaching linear behavior is not implicit with soft clipping, as it can be with log scaling.
SoftClip
The “half signal” for setting the soft clipper. The value set here is the input signal that will
become 0.5 as an output signal. Setting this to 0.0 turns the soft clipping off. Setting this to 0.5
is maybe the closest approximation to linear while on, but is not linear. Setting this to 1.0 will
match the derivative/slope of the output at zero input (so if you want the lowest forces to feel
similar, and compress everything else). Therefore, less than 1.0 will amplify some lower force,
and reduce larger forces. Greater than 1.0 will reduce all forces.
SoftClipUnity
Straight soft clipping will never reach full 1.0 magnitude, which means for lots of soft clipping
scenarios, the full force of the wheel is never quite used, possibly to a noticeable level.
SoftClipUnity sets the expected maximum force that will hit the soft clipper, and rescales such
that that force outputs at 1.0 (full force of wheel). This means saturation may be reintroduced if
this is set too low, but it is useful to fine tune output, especially when the soft clipper is used
more for non*linear response than for anti*saturation. Setting this to 0.0 turns the unity re*scaling
off.
Scoop
This is a new component, and is directly in response to some devices going flat in
response at higher force levels. This is somewhat the opposite non*linear tool as the soft
clipper, but is shaped differently, to better fit the nature of devices (and be easier to control).
So what scoop does is reduce lower forces more and high forces less, thereby increasing the
slope of force where some devices reduce the slope of force. Since devices seem to do this in
two more or less linear regimes, with a knee in between, this is how this component works (in
the opposite direction).
ScoopKnee
The input force level where the knee is at. If this is 0.0, this component is turned off.
ScoopReduction
The input force reduction below the knee. Above the knee, the force slope is increased such that
at 1.0 input force, the output force is 1.0.
Tighten Center
Note that the name of this can be confusing. This has nothing to do with tightening the wheel
about geometric top center. The “center” for this component means “zero force”, and has
nothing to do with wheel position.
The primary purpose of this is to remove wheel deadzones, but it can also be a shaping tool.
TightenCenterRange
This is the input force below which the output force is increased to remove a deadzone. Put
more simply, this is the size of the deadzone you are trying to remove.
TightenCenterFalloff
This controls how sharply the output force approaches zero force as the input force goes below
TightenCenterRange.
Damping
One use of damping can be to counter inherent drag in a device by using negative BaseDrag.
However, often devices do not have linear inherent drag, so setting BaseDrag such that there is
little to no device resistance at slow wheel speed will result in accelerating forces at higher wheel
speeds. This can be fixed by also having some positive BaseDragSqr.
A technique to set damping to cancel most device drag is to turn off ALL forces, Slow
Speed Force, and TireForce) and adjust BaseDrag and BaseDragSqr such that the wheel stays
the same speed or slows down ever so slightly (until it hits a stop) when you give it a good push
at different rates. It seems better to have a tiny bit of drag left than to have the wheel accelerate
on its own at any speed.
BaseDrag
This is resistance on the wheel as a function of wheel angular velocity.
BaseDragSqr
This is resistance on the wheel as a function of wheel angular velocity squared.
BaseDragLoPass
This is smoothing of the angular velocity for drag calculations. Raw position data on some
devices can be noisy. Note that increasing smoothing can have a secondary apparent effect of
increasing the effect of drag.
@Lazarou I expect you to get this perfect now lololololol
Input Signals
The four front tire input signals are the component parts of the whole tire induced torque coming
through the rack. So if these are all scaled to the same thing (by convention 1.0), this is the
same as straight rack torque.
The two rear tire signals are to enable the Seats of Pants concept. Neither of these go through
rack geometry though, as there is no rear rack and steering wheel. These just go straight to the
seat.
Finally, the G force signal is to enable the Gut physical simulation concept.
Tire Force
This is simply an overall multiplier on all of the input tire forces. Note that G forces, the input to Gut, are not
scaled with this parameter. Note that the other FFB parameter in the Controller section is the
same as the scaling in the driver. Reducing that does not help saturation, it simply reduces
force.
Spindle
SpindleMasterScale
This is a multiplier on all of the front tire forces. This was added to allow the following four scale
to default to 1, and be more intuitively like “weights”.
SpindleFxScale
SpindleFyScale
SpindleFzScale
SpindleMzScale
Individual scales on the components going through the spindle/rack. To get pure rack forces,
leave these all at the same value. 1.0 is a convenient value for this, and use SpindleMasterScale
to dial overall spindle force.
SpindleFxLoPass
SpindleFyLoPass
SpindleFzLoPass
SpindleMzLoPass
Individual smoothing on the components going through the spindle/rack. Typically Fx requires
more smoothing than the others. 0.0 is no smoothing. 1.0 is normalized to “really smooth but
still some useful signal”. Values above 1.0 are valid.
SpindleArm
SpindleArm is the angle, in degrees, of the attachment of the tie rod to the spindle. Zero degrees
means the tie rod is attached directly aft of the axis. That particular distance, how far aft, is not
critical, because that just amounts to scale, which we adjust based on squeezing into the device
range anyway. The angle though matters a lot in how the forces feel when the steering wheel is
not straight.
90 degrees is then with the tie rod directly inboard of the axis, which physically would result in the
inability to steer. Realistic values I'd guess are between 0 and 45..
Seat of Pants
The basic idea of “Seat of Pants” is to present information from what is happening at the rear of
the car through force feedback. There are two physical forces that are used. The rear side
loads and the rear vertical loads.
SoPScale
Overall scaling of Seat of Pants
SoPLateral
Scaling of the rear side load effect.
SoPDifferential
Scaling of the rear vertical load effect, which is actually the difference between right and left
vertical loads.
SoPLoPass
Smoothing of the Seat of Pants signal. 0.0 is no smoothing. 1.0 is normalized to “really smooth
but still some useful signal”. Values above 1.0 are valid.
Relative Torque Adjust
The idea here is to present torque to the wheel based
on the change in torque through time instead of as absolute torque. This means that with
reasonable parameters, the wheel will never fully saturate. But unlike soft clipping (which can
also prevent saturation), the high end torques do not get as heavily squeezed.
There is one side effect to tune out though, and that is the wheel losing center over time. If all
torque was completely via “Relative Torque Adjust”, centered torque would move around as the
wheel goes through previously saturating torques. To prevent this, we use the bleed value to
“bleed” absolute torque back into the mix.
RelativeGain
This is the scaling on the amount of calculated torque change that is applied. 1.0 is the intuitively
correct value. 0.0 turns this component off.
RelativeBleed
This is a time value for bleeding absolute torque back in. 1.0s is a good starting point.
RelativeClamp
This is the force to wheel value (so in the 0.0 to 1.0 range) where the non absolute running
magnitude is clamped. This does not clamp the overall value, and torques can still go above
this, but it does exert a strong clamping effect. 1.0 is a good starting point for this. Values
greater than 1.0 can make sense if soft clipping is also used. Values less than 1.0 makes sense
to give some headroom for spikes to be a little more symmetrical around the clamp.
Note that with this component on, and with clamp at 1.0 or less, and not too much bleed, there is
no full saturation. What this means is that what was too much force before now becomes more
force effects felt near full force. But this too can become too much, as that can start to
overpower the more subtle unsaturated force range. So you still need to dial overall force (via
Tire Force and the scales), but that scaling can become an interesting control, not just
something to avoid saturation with.
Gut Simulation
This is a simulation of the G forces on the body of the driver. Basically, G forces move the body
around via a physical simulation, and the result of that simulation is translated to force feedback.
GutScale
Magnitude of the gut simulation in FFB. 1.0 is normalized to “significant but not overpowering”.
GutLongScale
Magnitude of longitudinal effect applied. This is a scaling of the baseline lateral effect. At 0.0, the
gut effect will be all based on lateral G’s. With non zero GutLongScale, under braking G’s, the
lateral effect will increase, and under acceleration G’s the lateral effect will decrease.
GutMass
This is the mass of the simulated “gut”, which should not be the whole human body. It should be
some lesser portion, roughly being the effective amount of mass not “locked down” rigid by the
seat and seatbelts. This is a very fuzzy concept, so the number is really just a very rough
ballpark number. This is fine, because the simulation is not overly sensitive to this number. It
matters, but it is not extremely critical.
The default is 50 kg.
Arm Simulation
The arm simulation simulates that the wheel is driven by a non rigid linkage, namely the driver’s
arms, as well as play and mass in the linkages themselves.. However, this is done purely with
force feedback. The position of the the controller still directly dictates the location of the
simulation wheel.
This simulation also serves as the main global smoothing stage.
ArmScale
Ratio of incoming signal to pass through the arm simulation. 0.0 if off. 1.0 is application of all
incoming signal.
ArmMass
Mass of “arms”, with respect to simulation. This does not necessarily mean the average mass
of two human arms. This is the effective mass with respect to the degree of freedom that is the
wheel/controller.
ArmStiffness
Spring*like stiffness of the “arms”. Stiffer settings will pass through higher frequency
information. Softer settings will smooth more.
ArmDamping
This is a multiplier on critical damping of whatever mass and stiffness is set. Therefore, 1.0
means exactly critically damped.
Soft Clipping
This compresses all force within range of the wheel, although the stronger the force, the more it
is squeezed into the higher force range. In some ways this is like Log Scaling, but Soft Clipping
guarantees all signal will squeeze into the range, however compressed. On the other hand,
approaching linear behavior is not implicit with soft clipping, as it can be with log scaling.
SoftClip
The “half signal” for setting the soft clipper. The value set here is the input signal that will
become 0.5 as an output signal. Setting this to 0.0 turns the soft clipping off. Setting this to 0.5
is maybe the closest approximation to linear while on, but is not linear. Setting this to 1.0 will
match the derivative/slope of the output at zero input (so if you want the lowest forces to feel
similar, and compress everything else). Therefore, less than 1.0 will amplify some lower force,
and reduce larger forces. Greater than 1.0 will reduce all forces.
SoftClipUnity
Straight soft clipping will never reach full 1.0 magnitude, which means for lots of soft clipping
scenarios, the full force of the wheel is never quite used, possibly to a noticeable level.
SoftClipUnity sets the expected maximum force that will hit the soft clipper, and rescales such
that that force outputs at 1.0 (full force of wheel). This means saturation may be reintroduced if
this is set too low, but it is useful to fine tune output, especially when the soft clipper is used
more for non*linear response than for anti*saturation. Setting this to 0.0 turns the unity re*scaling
off.
Scoop
This is a new component, and is directly in response to some devices going flat in
response at higher force levels. This is somewhat the opposite non*linear tool as the soft
clipper, but is shaped differently, to better fit the nature of devices (and be easier to control).
So what scoop does is reduce lower forces more and high forces less, thereby increasing the
slope of force where some devices reduce the slope of force. Since devices seem to do this in
two more or less linear regimes, with a knee in between, this is how this component works (in
the opposite direction).
ScoopKnee
The input force level where the knee is at. If this is 0.0, this component is turned off.
ScoopReduction
The input force reduction below the knee. Above the knee, the force slope is increased such that
at 1.0 input force, the output force is 1.0.
Tighten Center
Note that the name of this can be confusing. This has nothing to do with tightening the wheel
about geometric top center. The “center” for this component means “zero force”, and has
nothing to do with wheel position.
The primary purpose of this is to remove wheel deadzones, but it can also be a shaping tool.
TightenCenterRange
This is the input force below which the output force is increased to remove a deadzone. Put
more simply, this is the size of the deadzone you are trying to remove.
TightenCenterFalloff
This controls how sharply the output force approaches zero force as the input force goes below
TightenCenterRange.
Damping
One use of damping can be to counter inherent drag in a device by using negative BaseDrag.
However, often devices do not have linear inherent drag, so setting BaseDrag such that there is
little to no device resistance at slow wheel speed will result in accelerating forces at higher wheel
speeds. This can be fixed by also having some positive BaseDragSqr.
A technique to set damping to cancel most device drag is to turn off ALL forces, Slow
Speed Force, and TireForce) and adjust BaseDrag and BaseDragSqr such that the wheel stays
the same speed or slows down ever so slightly (until it hits a stop) when you give it a good push
at different rates. It seems better to have a tiny bit of drag left than to have the wheel accelerate
on its own at any speed.
BaseDrag
This is resistance on the wheel as a function of wheel angular velocity.
BaseDragSqr
This is resistance on the wheel as a function of wheel angular velocity squared.
BaseDragLoPass
This is smoothing of the angular velocity for drag calculations. Raw position data on some
devices can be noisy. Note that increasing smoothing can have a secondary apparent effect of
increasing the effect of drag.
@Lazarou I expect you to get this perfect now lololololol
