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V2 Physics Discussion


griev0r

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I experience significant rear steer in the Sierra when under full power in a 'straight line'
From my limited experience driving on loose surfaces being perfectly straight when accelerating or braking is pretty rare and this was with a low powered RWD car compared to the Sierra. I would liken it to taking a low powered RWD car on snow, when the rear loses traction it rarely goes dead straight. I am not suggesting DIRT Rally is perfect in this respect but I would expect the rear end to be pretty wayward on anything remotely slippery.
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This video shows both how wrong the V1 behaves on tarmac, but also V2. The car is def not as planted on the road as the V1 cars, but at the same time it's not as "slidy" as the V2's. Somewhere in between I would say. :)

https://www.youtube.com/watch?v=cPaoNEip2H0
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I just took the Escort out on a Wales stage using the Rift and it was the most fun experience I have had rally driving on a computer and I have tried pretty much every title since Lombard RAC Rally in '89.

I enjoyed RBR and the recent mods (and the Rift update) but this has captured my imagination more somehow. It was one of those experiences where I don't really care how fast I was, I just enjoyed the drive!

For me at least I love how this is developing, great job so far!
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bogani said:
I experience significant rear steer in the Sierra when under full power in a 'straight line'
Not sure if serious? Ofc the car will step sideways on full power. Especially the Sierra where all the juice come when the turbo kicks in. :)
So yeah, serious but not in the way you think; it crazily steps out, not in the expected way, like I'm barely ever on full throttle, I have to play more though.
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bogani said:
This video shows both how wrong the V1 behaves on tarmac, but also V2. The car is def not as planted on the road as the V1 cars, but at the same time it's not as "slidy" as the V2's. Somewhere in between I would say. :)

https://www.youtube.com/watch?v=cPaoNEip2H0
You can clearly see the 'crabbing effect' in action in actual real life there. Colin only uses steering to initiate turn in to a corner.  Quite often, he's either straight or opposite lock by the apex and he's actually turning the corner with the throttle.

So many folk are complaining of this, but its totally accurate!!

I would say the grip he is achieving could, with a little time, be dialled into the in-game setup of the Focus by adjusting rake, rear suspension and diffs. 

I know @bogani has started a thread elsewhere inviting refined settings based on this video, & i'll be having a look at doing that this weekend.  I am fairly confident it'll not be too difficult (I have never really tried due to liking the oversteer)
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Kakkela said:
WasabiWei said:
It isn't a theory - the patch notes say FFB is off because of the reduced downforce. I'm not making this up..
I think he knows, the problem is people hear "downforce" and immediately knee-jerk to "aerodynamic downforce"
What other kind of downforce there is but aerodynamic downwards thrust? (Can't really be gravity, why would they change gravity???)
This is a game, forces aren't the same as real life and there are more of them to complete the simulation.  Gravity is one thing, weight is another, aero is one more, which I understand isn't modeled in v1 physics.
Gravity will affect how fast something falls, but you need downforce in the game to say how much force the car should exert on the ground.
Aero is modelled in v1 physics, it just wasn't really fleshed out until the hillclimb cars.
It was after that they went back to the v1 physics and found the aero downforce was exaggerated.
Gravity is a universal force in the game engine, it's not something that is tied to the individual car physics.
Different cars don't have different gravity settings.

In a realistic gravity simulation, weight doesn't matter at all. Heavier objects don't automatically fall faster than light objects.
It's aerodynamic forces such as drag (air resistance) which affect how quickly something falls.
Hence the old experiment that in a vacuum, a feather and a 500g weight fall at exactly the same speed.
The relevance of weight to gravity is in inertia.
Any decent downforce simulation needs to be tied to speed rather than gravity.
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Lets collect our sugestions together, so:
  1. "Presuming the weight is accurate (why would they change it) and presuming they REDUCED the downforce with V2: than the problem is somewhere in the Tyre-Physics. (Which is actually the hardest part of car-physics-simulation cause of the rubber/air/pressure/surface interaction which is in fluid-dynamics territory if you'd do it accuratly)"
  2. "The weirdness starts when you push things beyond the limit, can't really explain exactly what happens, it seems the car tries to correct itself in high speed slides, then you throw in some opposite lock and you're into the trees :v
    In tarmac is worse, in the tarmac grip changes occur much faster, so this weird center pivot pendulum effect becomes very noticeable/intrusive."
  3. "In real life when you steer too much, you'll get understeer. For some reason I think that the more you steer, the better turn-ability you have. Like there are no slip-angle calculations at all. (Yeah, I know that on rally tyres the optimum slip-angle can be past 10 degrees.)"
  4. "I think cars have way too much mechanical grip. On lower speed corners it feels like there's an infinite lateral and longitudinal grip. Cars does not resist to turn because of the locked differentials etc. For sure the coast lock is not very aggressive but you still need to lock it reasonably tight to keep the car stable under braking. That should also make the car a bit understeery on lower speed corners.
    Now there's just a bit too much mechanical grip and things like "point of no return" while sliding is missing. That makes driving a bit easier than it should be. You can always correct even you go way too wide or you don't have to fight to make the car to turn-in, etc... In general you don't get punished if you do stupid things."

Finally I would say that "..I think the new physics is a fair improvement. There is room for improvement though I think, but it's a step in the right direction. I don't think I could add much to the discussion as far as how to make it better though, it's so fun already..".

V2 is a grower, but we need V3!!






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@PiotrAS191 - I like your summary of some relevant points of discussion although I am not so sure about the slip-angle part. The most rally-ish car I have driven extensively (my reference point for what follows) is the MkI VW Scirocco. The only times the slip angle could be exceeded was in snow or on ice, at least at any speed sane for country road 'pushing it a little but not racing' since I don't drive like an ass on public roads. Even at 60 that thing would turn in HARD, partly due to the the twist-beam rear suspension that causes the rear-inside wheel to come up off of the road under hard turning, which makes it dive inside all of the sudden. My point is that I have doubts that rally cars can get the 'turned it too far, now the car is in a stuttering understeer' that I think the slip-angle comment is referring to. I have done that in old sedans, but not in any reasonably snappy car.

One thing I would add is that something seems off about flight characteristics. In V2 Finland has an unrealistic amount of hang time as well as too much loft off of rises and we get some pretty bizarre crash behavior like this: http://steamcommunity.com/sharedfiles/filedetails/?id=530286756 . Something is awry, but I can't pin-point what it is. It feels like some value was fudged to compensate for the exaggerated downforce in V1 and it was not changed back after the downforce was reduced for V2. I am not familiar enough with game engine parameters to make a decent guess. That is total spit-balling out of nowhere, just an impression I get. Maybe the air density is set to 'thick as syrup'? :persevere: 


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I'd like to restate what WasabiWei said. The cars have too much hang time. If reduced down force had this much of an effect on the cars then it seems gravity needs to be upped slightly to compensate. From there, the tire physics need to be worked on to meet the suggestions in this thread.

Again, the gravity needs to be fixed before they mess with tires or else they'll have to change things again later. Anyone who's new to this thread, refer to my video on the first page and you'll notice just how much of a change to the hang time took place.
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Made some more tests here, i don't discard the "crab-walk" issue, though it can be neutralized with some setup fiddling (it wasn't some nonsense setup BTW) it still happens when "venturing into the extremes"

But i'm starting to think it's more of a too much grip or rolling resistance issue than anything else, i've done some tests here with Wet conditions and mostly i feel like the wet grip should be used for the dry track, and the wet should be even less grippy.

I've recorded some small clips
https://www.youtube.com/watch?v=hfo8_RntTs8
1st clip, Fiesta at Germany: Perfect, if you ignore all the water :p
2nd clip, Impreza S7 at Finland: Great showcase for bodyroll/inertia
3rd clip, Focus WRC at Wales:  Nice slides everywhere, even made a great 4-wheel slide through the hairpin
4th clip, Focus WRC, Snow: If you're using Snow Tyres, yeah, that would be pretty much it. but this isn't the case.
5th clip, Focus WRC, Tarmac: Late slide into the corner, the car had some initial slide and then had some understeer to the exit, totally expected if the track was dry
6th clip, Focus WRC, Hairpin: The slide itself could've been better, but the behavior was what i expected to be if the track was dry

BTW, the Focus was the only one i've taken the time to make a good setup, the original was very bad (in fact, in all cars the default sucks)

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I have another video clip that demonstrates bad flight characteristics after a collision event. This one is with a track marking flag, which leads me to suspect collision forces more than plain old gravity. After the collision the flag seems to have less than zero mass, like there is a negative multiplier applied to weight when a collision is computed, or something, I dunno. Instead of going forward and down it goes up and back. I have seen other strange flag behavior, but it is hard to judge whether it is always opposite of normal physics or not, usually it just looks like a weird flag-ricochet flying into space after a hit, sometimes forward, but always spinning upright and flying off in some direction really fast.
https://www.youtube.com/watch?v=8mHzFl0-0gI
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WasabiWei said:
I have another video clip that demonstrates bad flight characteristics after a collision event. This one is with a track marking flag, which leads me to suspect collision forces more than plain old gravity. After the collision the flag seems to have less than zero mass, like there is a negative multiplier applied to weight when a collision is computed, or something, I dunno. Instead of going forward and down it goes up and back. I have seen other strange flag behavior, but it is hard to judge whether it is always opposite of normal physics or not, usually it just looks like a weird flag-ricochet flying into space after a hit, sometimes forward, but always spinning upright and flying off in some direction really fast.
https://www.youtube.com/watch?v=8mHzFl0-0gI
I don't think the flying flag is evidence of anything other than crappy flag physics. Why should they bother modelling flags well and why does what flags are doing somehow relate to the car physics?

You're reading way too much into hitting flags, although I acknowledge hitting flags can be unrealistic and annoying, it's just got nothing to do with car collisions and handling.
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WasabiWei said:

One thing I would add is that something seems off about flight characteristics. In V2 Finland has an unrealistic amount of hang time as well as too much loft off of rises and we get some pretty bizarre crash behavior like this: http://steamcommunity.com/sharedfiles/filedetails/?id=530286756 . Something is awry, but I can't pin-point what it is. It feels like some value was fudged to compensate for the exaggerated downforce in V1 and it was not changed back after the downforce was reduced for V2. I am not familiar enough with game engine parameters to make a decent guess. That is total spit-balling out of nowhere, just an impression I get. Maybe the air density is set to 'thick as syrup'? :persevere: 


I like that example, but I don't think it's evidence of flight issues as much as it is highlighting that cars in the game "bounce" off objects more because they don't absorb the energy through deformation. In real life you would bend tear and snap all the metal and the front and underneath of the car when you hit the rock like that, which would send the car on a completely different trajectory.

I do wonder how they model aeroforce though, is it just relative to speed or is orientation a factor like it would be in real life? Do you get more lift when you are accelerating?
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WasabiWei said:

One thing I would add is that something seems off about flight characteristics. In V2 Finland has an unrealistic amount of hang time as well as too much loft off of rises and we get some pretty bizarre crash behavior like this: http://steamcommunity.com/sharedfiles/filedetails/?id=530286756 . Something is awry, but I can't pin-point what it is. It feels like some value was fudged to compensate for the exaggerated downforce in V1 and it was not changed back after the downforce was reduced for V2. I am not familiar enough with game engine parameters to make a decent guess. That is total spit-balling out of nowhere, just an impression I get. Maybe the air density is set to 'thick as syrup'? :persevere: 


I like that example, but I don't think it's evidence of flight issues as much as it is highlighting that cars in the game "bounce" off objects more because they don't absorb the energy through deformation. In real life you would bend tear and snap all the metal and the front and underneath of the car when you hit the rock like that, which would send the car on a completely different trajectory.

I do wonder how they model aeroforce though, is it just relative to speed or is orientation a factor like it would be in real life? Do you get more lift when you are accelerating?
I may be reading too much into this, but aero force could also be the reason for the goofy flag behavior for all we know. I know it seems far out there. The behavior is driving me nuts though! The lack of car deformation explanation seems inadequate to me. If that were all that was wrong cars would not fly as if the air were thicker than normal.
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As far as car deformation, if you really, really try you can tear these cars apart pretty good visually.  Wheels/tires come off, hatches open and bounce around, windows crack, hoods get smashed in, I think visually they are going as far as they can.  Problem is other than tire punctures you don't really feel it in the driving model.  Tire punctures are seriously hard to drive with and that's a nice feature, but when I hit a tree at Finland at 100+mph I shouldn't be able to drive away with it with a smoking radiator and no other consequences.  I feel like the basics are there, they are just dialed way back, probably to meet manufacture's requests to getting a licensed car.  People have to realize that car companys don't want their vehicles represented in a game/sim as a smoldering pile of shit.  Wish there was an option for damage level like RSRBR has in place with off/reduced/safe/realistic, but I don't see that happening because of licensing issues.  I'd love to see a more realistic/harsh damage model implemented, but as said with all licensed cars you have to realize Codies can only go so far.  Terminal damage is implemented but it's really hard to get to that level unless you drive off a mystery cliff in Monte Carlo.
 
Crash physics are on the floaty side with just getting catapulted into the air and after landing minimal damage done.  But, have to take it with a grain of salt.  Look at BeamNG, that is a basically a tech demo of how crashes should be and is the most advanced in the gaming world but its far from perfect.  Softbody physics are in an infancy and you can't expect it at this time in an actual game instead of a glorified tech demo.  When your rally car rolls down a stage of course you want to see it getting torn apart but it isn't viable yet.  I think the damage model is already pretty extensive visually and physically, but just dialed way, way back. 

Anyways, crash physics can be cool like Wreckfest and the mentioned BeamNG... but I'd much rather they focus on the actual driving model 100% more.  That is what really counts.
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griev0r said:
As far as car deformation, if you really, really try you can tear these cars apart pretty good visually.  Wheels/tires come off, hatches open and bounce around, windows crack, hoods get smashed in, I think visually they are going as far as they can.  Problem is other than tire punctures you don't really feel it in the driving model.  Tire punctures are seriously hard to drive with and that's a nice feature, but when I hit a tree at Finland at 100+mph I shouldn't be able to drive away with it with a smoking radiator and no other consequences.  I feel like the basics are there, they are just dialed way back, probably to meet manufacture's requests to getting a licensed car.  People have to realize that car companys don't want their vehicles represented in a game/sim as a smoldering pile of shit.  Wish there was an option for damage level like RSRBR has in place with off/reduced/safe/realistic, but I don't see that happening because of licensing issues.  I'd love to see a more realistic/harsh damage model implemented, but as said with all licensed cars you have to realize Codies can only go so far.  Terminal damage is implemented but it's really hard to get to that level unless you drive off a mystery cliff in Monte Carlo.
 
Crash physics are on the floaty side with just getting catapulted into the air and after landing minimal damage done.  But, have to take it with a grain of salt.  Look at BeamNG, that is a basically a tech demo of how crashes should be and is the most advanced in the gaming world but its far from perfect.  Softbody physics are in an infancy and you can't expect it at this time in an actual game instead of a glorified tech demo.  When your rally car rolls down a stage of course you want to see it getting torn apart but it isn't viable yet.  I think the damage model is already pretty extensive visually and physically, but just dialed way, way back. 

I highly doubt licensing is keeping them from making a better damage model. I'm assuming it's not easy to create a new visual damage model and they could see other things as a higher priority.  I just want a setting where my car breaks more easily, I'm sure that aspect will be addressed in the future once they knock some other stuff off their to do list. 
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griev0r said:
As far as car deformation, if you really, really try you can tear these cars apart pretty good visually.  Wheels/tires come off, hatches open and bounce around, windows crack, hoods get smashed in, I think visually they are going as far as they can.  Problem is other than tire punctures you don't really feel it in the driving model.  Tire punctures are seriously hard to drive with and that's a nice feature, but when I hit a tree at Finland at 100+mph I shouldn't be able to drive away with it with a smoking radiator and no other consequences.  I feel like the basics are there, they are just dialed way back, probably to meet manufacture's requests to getting a licensed car.  People have to realize that car companys don't want their vehicles represented in a game/sim as a smoldering pile of shit.  Wish there was an option for damage level like RSRBR has in place with off/reduced/safe/realistic, but I don't see that happening because of licensing issues.  I'd love to see a more realistic/harsh damage model implemented, but as said with all licensed cars you have to realize Codies can only go so far.  Terminal damage is implemented but it's really hard to get to that level unless you drive off a mystery cliff in Monte Carlo.
 
Crash physics are on the floaty side with just getting catapulted into the air and after landing minimal damage done.  But, have to take it with a grain of salt.  Look at BeamNG, that is a basically a tech demo of how crashes should be and is the most advanced in the gaming world but its far from perfect.  Softbody physics are in an infancy and you can't expect it at this time in an actual game instead of a glorified tech demo.  When your rally car rolls down a stage of course you want to see it getting torn apart but it isn't viable yet.  I think the damage model is already pretty extensive visually and physically, but just dialed way, way back. 

Anyways, crash physics can be cool like Wreckfest and the mentioned BeamNG... but I'd much rather they focus on the actual driving model 100% more.  That is what really counts.
I think the damage is just poorly calibrated... sometimes i get the expected damage from minor hits, but mostly it's just a full stop plus a shattered windshield
The collisions are another problem, seems like the body doesn't absorb the forces, it just bounces back or get stuck into whatever you hit, this was way better modeled in the older DiRTs, DiRT2 being the best in this area
The visual deformation and mechanical damage hands down goes to the first DiRT (you barely could get away when going though a bush, and if you did, your driveshaft was probably laying on the ground)
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You'd be surprised at what stops damage models, historically, even if it's not the case here, damage models have always had to be severely restricted for licensed cars.
That's easily one of the dumbest things I've ever heard. 

edit: you're not dumb the fact that its restricted is dumb. 
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AphDburn said:
You'd be surprised at what stops damage models, historically, even if it's not the case here, damage models have always had to be severely restricted for licensed cars.
That's easily one of the dumbest things I've ever heard. 

edit: you're not dumb the fact that its restricted is dumb. 
It's true, an example is Project Cars, most cars can lose parts like bumpers and doors, But all Mercedes have a restricted model so no Doors or any other damage can be made to the passenger-cell of the car. Not even spoilers come off only bumpers. All because Merc said it should be that way if you want the licence
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