Horizon physics research thread

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571
Czech Republic
Czech Republic
Hi, I would like to start research thread about Horizon series. I always have too many questions and not enough answers and I am not alone I guess. We could find anything interesting about physics and handling here. Many things need a lot of testing and more people is necessary.

TOPICS:

What do you thing about gravity in Horizon? Is it real, lower, higher and why?

Do you think cars are much lighter in Horizon than Motorsport? Looks like it to me.

What about front grip while steering on a controller? I think the front grip is too high and it destabilize the whole car like in no other game.

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Gravity was definitely the real value on the 360 games at least - can't remember if it was listed in the tunable settings or the database though.
 
571
Czech Republic
Czech Republic
That's possible, no crazy jumps there :D I am not sure, gravity looks lower. But I don't know how normal car jumps over the huge bumps.
 
571
Czech Republic
Czech Republic
How can we reasearch it without telemetry?
It's easy. Take all possible games on the market and compare it. Trust more true sims than others. And you have eyes too I guess so you can see if a car behaves strangely.

I played Forzas the most so I have most questions there because they have many strange stuff I want to research :D Horizon is more interesting because we need to find all differences from "real" Motorsport physics.

If you don't like it's OK, I like to know everything about games I play.
 
The only real difference between the Motorsport and Horizon games, at least initially, is the tyres. FM4's tyre data in FH1 drives more or less like FM4 does.
 
571
Czech Republic
Czech Republic
The only real difference between the Motorsport and Horizon games, at least initially, is the tyres. FM4's tyre data in FH1 drives more or less like FM4 does.
Sounds good, I will test it. I always had a feeling, H1 is very good. Physics is still the same but in H4 cars must be lighter I guess.
 
7,622
Denmark
Denmark
It's easy. Take all possible games on the market and compare it. Trust more true sims than others. And you have eyes too I guess so you can see if a car behaves strangely.

I played Forzas the most so I have most questions there because they have many strange stuff I want to research :D Horizon is more interesting because we need to find all differences from "real" Motorsport physics.

If you don't like it's OK, I like to know everything about games I play.

It's not that I don't like it. Some clarification on what to expect just seemed necessary.

I've noticed some things.
  • FM7 has more suspension travel than FH4, and I actually think it feels exaggerated in FM7 to the point where FH4 feels more natural.
  • Cars appear to turn more easily in FH4 compared to FM7.
  • Friction between tires and surface feels more pronounced in FH4 compared to FM7.
  • Snow grip on FH3 Blizzard Mountain was really unforgiving compared to FH4 winter season.
 
571
Czech Republic
Czech Republic
It's not that I don't like it. Some clarification on what to expect just seemed necessary.

I've noticed some things.
  • FM7 has more suspension travel than FH4, and I actually think it feels exaggerated in FM7 to the point where FH4 feels more natural.
  • Cars appear to turn more easily in FH4 compared to FM7.
  • Friction between tires and surface feels more pronounced in FH4 compared to FM7.
  • Snow grip on FH3 Blizzard Mountain was really unforgiving compared to FH4 winter season.

Wow, that's exactly it! Because I don't have enough time and everybody can see something else it's important to have more researchers.
  • Suspension travel could be because of lighter cars? Because if H4 has lighter cars and lower gravity, it should be lower.
  • Exactly, lighter cars should be better for turning and higher grip helps too.
  • Yes, higher grip in H, I think so too.
  • Yes.
 
1,207
United Kingdom
United Kingdom
breeminator
breeminator
What about front grip while steering on a controller? I think the front grip is too high and it destabilize the whole car like in no other game.
This depends on the tune, you can make a car have less front grip than rear grip if you want. But because the meta, in S2 at least, is to have higher front downforce than rear downforce, the balance between front and rear grip changes with speed, so if you maximise turning ability at lower speeds it will inevitably be a bit oversteery at higher speeds.
 
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571
Czech Republic
Czech Republic
This depends on the tune, you can make a car have less front grip than rear grip if you want. But because the meta, in S2 at least, is to have higher front downforce than rear downforce, the balance between front and rear grip changes with speed, so if you maximise turning ability at lower speeds it will inevitably be a bit oversteery at higher speeds.
I use mostly stock cars and it's for every Forza. I am not sure, maybe I am wrong but it feels like you have some artificial grip helper on front. It's like counter steering, you can do it even without possible grip, it's just waiting for you there. It's probably for gamepad only.

Strange thing is I can't replicate Forza behavior in Project cars 1 or Assetto Corsa. It looks like you have a bit better grip on front wheels. I hope because of a gamepad but maybe it's different physics/handling. Or maybe I am just wrong, hard to say.
 
8,814
United States
Marin County
I've noticed a tendency for cars to exhibit unrealistic amounts of high-speed oversteer (with a gamepad, never played a Forza title with a wheel) since FM2. I remember first noticing it taking the kink at Road America in a stock Shelby GT500 and on every lap, the back end would step out at 130+mph. I've never seen a car in real life do something like this unless somebody purposefully was feinting the car into a corner to drift or historic race cars doing 4 wheel drifts around the track, but that's not really oversteer.. Here's an example:

go to 1:25

Maybe the gamepad allows for the steering to do things not normally possible in real life and that is a contributing factor. But high speed stability in cars without aero has always felt wrong to me in Forza games. I do think that the Forza engine, under the hood, boosts front end grip when certain limits are exceeded, even with simulation steering. Something like this: If velocity > 100mph & front steering angle > 20 degrees than boost front grip by X% kind of buff (obviously, I'd guess its a proportional formula, not a series of steps). I would guess that if this does exist, it would be so that gamepad players are not constantly overdriving the front end of the car with too-aggressive inputs. If you play a game like Project Cars, NFS Shift, or even Mafia Remastered, with simulation steering on a pad, it is incredibly easy to exceed the front end grip completely (with just steering angle) and plow off the road. It's basically impossible in Forza, you never truly lose the front end unless you disable ABS and lock up the front tires. Yes, understeer happens but it's not the "terminal" variety, merely the "hey, back off a little" type.

I think the other part to factor in is the assisted steering mode in Forza. We all know that it uses some sort of inertia buff to help control oversteer. To me it feels pretty unnatural, like driving in 90 weight motor oil. But what would feel even more unnatural is if it reduced understeer instead - you would literally see the front end of the car pivot in a corner. So I think the developers have set up the core physics and the individual car setups to be either neutral or oversteery and then count on better players being able to manage it and unskilled players to use the assists to keep it under control.

The weird thing is that from what I've seen, even when using a wheel, there is still some amount of artifice going on with the controls.

All of the above is why I almost cannot stand driving anything faster than A class cars. Cars in Forza feel less and less realistic (not to mention less fun) the faster you go, IMO.
 
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571
Czech Republic
Czech Republic
@Eunos_Cosmo Exactly, oversteer is the result of it.

Normal Forza has gamepad helper to not to exceed front angle by guarding your outer tire grip. That's fine but still front tire grip is somehow boosted (probably). So you don't exceed max grip and has some added. Losing front grip is very rare which is very strange to me.

If you think about Horizon, there is high stabilization so if you lose something, probably your rear-end because your front turned the whole car, stabilization kicks in. And front grip is still crazy high so you can do very strange stuff then. That could be your oversteer buff.

To me, it looks like sim physics with some strange helpers. You should lose your front more often I guess. On the other hand Gran turismo has understeer tendency for everything because it doesn't allow you to steer enough AND stabilization is there the same as in Horizon but even higher. So it depends what is the real problem.

That's true, steering in Forza is a bit tricky because of it because you need to know exact speed BEFORE. In normal sims you have speed which could work but you accommodate to a car behavior. In Forza, you try and lose your front outer tire and then the whole back and you can only countersteer. In Horizon, counter steering is highly automated, in Motorsport simulation steering has it real but front grip buff is there and it's crazy high. I think counter steering mode has higher buff than steering.
 
571
Czech Republic
Czech Republic
According to telemetry in Horizon, if you lose front grip, you are still able to turn relatively good and maybe that's the problem. But currently I am not sure how good front wheels without grip should be. Maybe it's fine.
 
13,878
United States
Los Angeles, CA
lImaRobotl
It's easy. Take all possible games on the market and compare it. Trust more true sims than others. And you have eyes too I guess so you can see if a car behaves strangely.

I played Forzas the most so I have most questions there because they have many strange stuff I want to research :D Horizon is more interesting because we need to find all differences from "real" Motorsport physics.

If you don't like it's OK, I like to know everything about games I play.
Why would you compare it to other games, rather than real life?
 
571
Czech Republic
Czech Republic
Why would you compare it to other games, rather than real life?
It's clear I guess. You can compare games but can't reality. I don't care how reality works if I can switch controller and play different game and feel it. It's like sim racing guys. They usually can't agree on anything. Who cares then. It's about comparison, not real life. I met many people who thought unreal physics is real physics. It's useless comparison for games.
 
8,814
United States
Marin County
One thing I noticed recently is that there doesn't appear to be any or at least very little aerodynamic drag when you are in the air. Hit a large jump at 200mph and see how slowly the speed reduces while in the air. This could be part of the reason the "gravity" seems wrong. Then take the same car and accelerate to 200mph on the highway, and then let off. The speed reduces far more rapidly. I appreciate that rolling resistance exists, but it's very marginal compared to aerodynamic drag. I don't think the Forza engine is capable of simulating free-body physics so when cars leave the road it's all very approximate. How would you even calculate the rate of deceleration if aerodynamic drag is not an actual parameter of simulation but rather, I suspect, a preset force-vector multiplier that only really works when the car is on the ground.
 
571
Czech Republic
Czech Republic
Air physics should be some magic. I am not sure about the gravity but cars fly a lot. The car momentum is sure thing to me, it's very small. Maybe they build some magic around it. You can't fly too much with small momentum so maybe they help a bit.

But ground and air physics as separate things makes sense a lot. On a ground you have full Motorsport but in the air it's pure fantasy. You can use aerodynamic parts in the air to navigate the car so there must be something.

Last time I played I had a feeling like countersteering moves the whole car without checking tires at all but I am not sure. It was interesting, I did countersteer and the whole car turned crazy fast.
 
571
Czech Republic
Czech Republic
Today I fired up Horizon 4 for few mins but the front grip was too high. I don't know what is wrong with every Forza but every car in stock tuning has very high front grip. Is it tuning? Maybe, I will try it next time. It's so hard to control any car after playing simulations only. Something is wrong there :D But it could be stock tuning. It's strange then for what it is there.

911 are most visible but it's almost in any car.
 
8,814
United States
Marin County
Today I fired up Horizon 4 for few mins but the front grip was too high. I don't know what is wrong with every Forza but every car in stock tuning has very high front grip. Is it tuning? Maybe, I will try it next time. It's so hard to control any car after playing simulations only. Something is wrong there :D But it could be stock tuning. It's strange then for what it is there.

911 are most visible but it's almost in any car.

After a lot of testing, I've found that increasing front rollbar stiffness a lot with no other changes seems to help. I don't think rollbar stiffness is adequately/accurately pre-set on most cars. That combined with ...whatever the engine is doing under the hood to make the game user friendly on a gamepad (namely some sort of grip-threshold-limited steering angle modifier and maybe a grip modifier too) makes the cars feel like they rotate around the front axle.
 

AOS-

Premium
28,705
Canada
'Sauga, ON
I don't have much to contribute on here, but if anything, I think race tyres should really perform a lot worse than it currently does on partly-snowed roads. I question why the off road wheels sometimes perform worse than it at times.
 

Wolfe

Physics Critic
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13,399
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Wisconsin
Wolfe2x7
After a lot of testing, I've found that increasing front rollbar stiffness a lot with no other changes seems to help. I don't think rollbar stiffness is adequately/accurately pre-set on most cars. That combined with ...whatever the engine is doing under the hood to make the game user friendly on a gamepad (namely some sort of grip-threshold-limited steering angle modifier and maybe a grip modifier too) makes the cars feel like they rotate around the front axle.
The way I describe the phenomenon is that in Forza games, it's as if every car sends some torque to the front wheels. The way the front wheels dig in and pull you out of oversteer makes for truly impossible recoveries...and it can really, really screw with your head if you are accustomed to more realistic drift trajectories. Now that I have a decent PC with a W10 partition, Forza's wonky oversteer control is a leading reason why I'm still not interested. I wouldn't mind the games being forgiving as much if I didn't have to un-learn my driving technique to play. :boggled:

I'm curious what they may have in store with the physics while they've been doing this "pause" on the franchise.
 
571
Czech Republic
Czech Republic
After a lot of testing, I've found that increasing front rollbar stiffness a lot with no other changes seems to help. I don't think rollbar stiffness is adequately/accurately pre-set on most cars. That combined with ...whatever the engine is doing under the hood to make the game user friendly on a gamepad (namely some sort of grip-threshold-limited steering angle modifier and maybe a grip modifier too) makes the cars feel like they rotate around the front axle.
OK, I will test it. What I remember, I increased rear grip and it was much better. Need to retest it.

Grip modifier is a question to me because it looks there is some kind of tarmac magnet on front wheels. What I think, it's not that easy to hold full grip on front all the time but in Forza you have it almost always ready for you. It's hard to separate helpers and physics then.

I don't have much to contribute on here, but if anything, I think race tyres should really perform a lot worse than it currently does on partly-snowed roads. I question why the off road wheels sometimes perform worse than it at times.
Snow is not real at all. The problem is Forza has only tarmac physics, everything else is fake. And Horizon should be accessible so they chose brutal high grip on snow. Which is not bad, but doesn't feel real. What I saw in adventure, offroad tires are unbetable on famous GT40.

The way I describe the phenomenon is that in Forza games, it's as if every car sends some torque to the front wheels. The way the front wheels dig in and pull you out of oversteer makes for truly impossible recoveries...and it can really, really screw with your head if you are accustomed to more realistic drift trajectories. Now that I have a decent PC with a W10 partition, Forza's wonky oversteer control is a leading reason why I'm still not interested. I wouldn't mind the games being forgiving as much if I didn't have to un-learn my driving technique to play. :boggled:

I'm curious what they may have in store with the physics while they've been doing this "pause" on the franchise.
Yeah, it's possible :D Counter-steering is strange because Forza uses faster steering for it. And the grip doesn't feel right too. You can't normally counter-steer as you wish because you need to have some grip on front. What I saw in Horizon (high counter helper), the car turns on it's own when you counter. But I am not completely sure.

Exactly, I can drive, for instance, PC1, PC2, AC, ACC, AMS1 and AMS2 easily and then switch to Forza and I can't drive :D
 
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8,814
United States
Marin County
The way I describe the phenomenon is that in Forza games, it's as if every car sends some torque to the front wheels. The way the front wheels dig in and pull you out of oversteer makes for truly impossible recoveries...and it can really, really screw with your head if you are accustomed to more realistic drift trajectories. Now that I have a decent PC with a W10 partition, Forza's wonky oversteer control is a leading reason why I'm still not interested. I wouldn't mind the games being forgiving as much if I didn't have to un-learn my driving technique to play. :boggled:

I'm curious what they may have in store with the physics while they've been doing this "pause" on the franchise.

Today I went in search of understeer...and I couldn't find it. I thought...well lets test some cars that should be prone to understeer

Audi RS2 Avant - Big heavy turbo straight 5 mounted in front of the front wheels. To be fair, I would expect turn in bite and then just miles of plowing. You get it up to speed and it's just ass-out oversteer

VW Corrado - FWD version of the same above and same result

1931 Bentley 8 Liter - This car has 175-width front tires and it's 90 years old. But somehow, it still refuses to push on turn-in. The ass just comes out immediately. I put the widest tires I could on the back and maximized front ARB stiffness. That made it slightly understeery on turn in, but not dramatically so.

VW Notchback - Ok so if the car with the most weight over the front oversteers, maybe the opposite configuration won't. Nope. Still loses its ass on turn in. I have to say the axis of rotation feels different though. It's like the pendulum is flipped around and the center of rotate is at the back...but it still oversteers on turn in.

I feel like it's something inherent with the Forza physics model. It's like the front tires have only parameters for static side-to-side grip levels and momentum/inertia has no effect on how they behave when you turn in. So whether you turn in at 35mph or 150mph you get the same bite from the front end. I think this particularly impacts cars with very fast steering. Inertia clearly acts on the overall physical body of the car though, so once you get that unrealistic amount of turn-in input, the ass just naturally comes around. I've noticed at lower speeds, all of the above cars handle somewhat rationally and it would explain (at least in my eyes) why cars feel so much worse the faster you go. Whenever I have to drive my silly Mosler to get a seasonal speed trap/zone the behavior of that car at high speeds just seems like pure fantasy - it's not especially hard to drive, it just feels so strange.

All of this would explain why my 996 GT3 is such a bear to drive. It's fast enough to reach speeds where the physics engine kind of comes undone, it's has incredibly fast steering, it has poor aero balance, and it's rear engined. So I think this is what is happening. At 140mph on the highway, I initiate a slightly steering input (lets say to change lanes) but the steering is very fast so it gives maybe more angle than I really want. Then because the tires don't really lose any horizontal/x-axis grip due to forward inertia, the front end of the car immediately bites and turns in like it's doing 40mph. The inertia of the car almost immediately starts to rotate around those front wheels. Then the rearward bias combined with too little rear downforce exaggerates the motion and the car. Any correction/counter-steer basically pushes the whole carnival ride the other way into an uncontrollable tank slapper. At least that's my theory. :lol:
 

eran0004

Premium
9,724
Sweden
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eran0004
Here is one experiments you can do without telemetry:

Lateral grip:
1. Find a roundabout (or some other well defined circle).
2. Drive around it slowly at a constant speed to measure the radius (r = v*t/(2*pi), where v is the speed of the car and t is the time to complete a full circle).
3. See how fast you can go around the roundabout.
4. Calculate the centripetal force (F = mv^2/r, where m is the mass of the car).
 
571
Czech Republic
Czech Republic
Today I went in search of understeer...and I couldn't find it. I thought...well lets test some cars that should be prone to understeer
That's exactly my problem with Forza and gamepad. It's strange nobody cares. It's almost in every car and rear heavy cars are the worst. Need to think about it more but your observations are exactly like mine.

I think it could be different on a wheel.
 
8,814
United States
Marin County
I am curious...who here actually plays Horizon with a wheel? I think it would actually help a lot. The fundamental problem (ie too much front grip, for whatever reason) isn't going to go away, but having precise control over the steering angle would seemingly make it a mute point.

*I want to clarify my previous post. Cars like the Audi RS2 and VW Corrado do understeer but only after they have settled into a corner. Every car I've driven, unless modified, has a tendency to oversteer at turn-in and the problem gets worse the faster you go. It's less of a problem for actually cornering (it's more of annoyance) and more a problem for making minor/slight turns at high speeds. I did find that adjusting the deadzone range for the steering to 30-40 helps a lot because at least the majority of the thumstick range is given to the initial 40% of the actual steering range. I wish there was an option to slow steering input globally or at least have a speed sensitive steering slider.
 
571
Czech Republic
Czech Republic
@breeminator is Horizon wheel expert. My guess is this front grip is something for gamepad only. Maybe it works better with assists? But then there is Motorsport and it's completely the same.

I was able to drive cars very good but it's very annoying. Currently I play simulations only and Forza steering is so strange after. I never liked Motorsport because of it, it's rahter funny. Horizon has lighter cars and stabilization assist so it's a bit better. Motorsport is not unplayable to me but it's very boring and I don't want to play it at all.

Currently I play the most Automobilista 2 and every time I play it it's so good. You really enjoy normal driving. Connection with the car is almost perfect. Or PC1 on gamepad is amazing. Forza is rather boring but sometimes fun.