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gabester

Accurized the speedometers!

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gabester
, 02-06-2014 at 09:23 AM (13110 Views)
So we found an interesting phenomenon - the very small expansion of the tires at speed (which is as minimalized as we can make it) was causing all the cars' speedometers to read low (compared to their actual speed). Basically, as the wheel expands, it covers more ground with less rotational velocity - so the wheel speed becomes lower than the air speed. Real tires expand a little bit, but not as much as the ones in BeamNG. If we stiffened the anti-expansion beams any more they'd explode (that's just a limitation we have to live with).

I recalibrated all of the speedometers so that they read about 1-2 mph above actual speed at high speed, just like a real car The Bolide used to read 160 mph when it was going 165, for example. Now it reads about 166-ish. All of the other cars are now accurate or read slightly high, whereas they all used to read around 2-4% below actual speed. Just another small change coming in the race update

And yes, we are still plugging away "behind the scenes" on everything else. Stay tuned
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  1. Davidbc's Avatar
    Good For those who don't know:

    The formula is: v = w · r

    v = linear velocity

    w = angular velocity (rotational velocity of the wheel)

    r = radius of the wheel

    So increasing the radius would increase the speed, but the game would be calculating the speed with the non-expanded wheel radius, hence the lower speed reading.
  2. gabester's Avatar
    Quote Originally Posted by Davidbc
    Good For those who don't know:

    The formula is: v = w · r

    v = linear velocity

    w = angular velocity (rotational velocity of the wheel)

    r = radius of the wheel

    So increasing the radius would increase the speed, but the game would be calculating the speed with the non-expanded wheel radius, hence the lower speed reading.
    Yup, that's exactly right. We can't easily measure the expansion of the tire on the fly, but we can recalibrate the speedometers to compensate

    I also just discovered that the tires on the T75 were about 10% too big in diameter. I corrected that, and also adjusted some other proportions (lowered top of hood/cab by 5cm, narrowed fenders and bumpers by 3cm on each side). It looks and is more realistic now.
  3. amegaara's Avatar
    you mentioned that "thats a limitation we need to live with"

    is this temporary until you find a better solution? or will we be stuck with this?


    and is the expansion so miniscule that it wont effect the cars performance?
  4. gabester's Avatar
    Quote Originally Posted by amegaara
    you mentioned that "thats a limitation we need to live with"

    is this temporary until you find a better solution? or will we be stuck with this?


    and is the expansion so miniscule that it wont effect the cars performance?
    Yes, the expansion is very small - like I said, it's around 2-4%. So it does affect gear ratios and top speed, but only by that very small margin. Of course 2-4% becomes very noticeable on a speedometer when you're going 165 mph. I noticed this discrepancy when top speed testing the Bolide with the recently added V-beams.

    And yes, like some flaws with our physics - at the current time there is just no more "room" to make it stiffer. If you make something too stiff in our physics engine, it simply explodes, which means that we cannot make some things quite as rigid as reality (though we can get close). If we increased the physics engine from 2000 fps to 2500 fps, we could stiffen everything, but that would also tax the CPU more, hurting framerates and making the multiple vehicle situation even worse. Although the 25% physics speedup coming in the race update is a big help
  5. Gridian's Avatar
    Exploding tires?

    Video or it did not happen ;-)

    On a more serious note: You're doing excellent work! I have had lots of hours of fun seeing into which shapes I can reshape those beautiful cars or just driving around. Thank you!

    Gridian
  6. AbdulAziz's Avatar
    I noticed the tire expanding when i flipped the pickup and it had an engine mod, when i pressed the gas the tires got really big...
    Can you show us pictures of the new cars that you are working on?
  7. fatboy's Avatar
    Quote Originally Posted by gabester
    If we increased the physics engine from 2000 fps to 2500 fps, we could stiffen everything, but that would also tax the CPU more, hurting framerates and making the multiple vehicle situation even worse.
    I have noticed that along with the tire expansion, the metal rim of the tire expands too, basically the whole wheel, which of course is not real.
    Thank you gabester for explaining why this is happening, at least for the moment.
  8. gabester's Avatar
    Quote Originally Posted by fatboy
    I have noticed that along with the tire expansion, the metal rim of the tire expands too, basically the whole wheel, which of course is not real.
    Thank you gabester for explaining why this is happening, at least for the moment.
    Yes, like I've said, there is unfortunately a limit to how stiff we can make things. We are lucky it is only a 2-4% change in diameter at very high speeds, so the effect is negligible.
  9. HighDef's Avatar
    I modified one of the golf carts to do 270mph~ and the wheels would double in size at this speed!
  10. gabester's Avatar
    Quote Originally Posted by HighDef
    I modified one of the golf carts to do 270mph~ and the wheels would double in size at this speed!
    Sounds like someone's expansionSpring is too low! The Bolide 390 GTR will happily cruise at 190 mph without much wheel expansion.
  11. Zulnex's Avatar
    Keep up the great work Developers.
  12. Callisto89's Avatar
    Hey, so there's a speedometer now ? :P
    Also you can't just bind it to the output of the transmission ?
  13. The Maximum's Avatar
    This...just..awesome! Implement the basic physical laws instead of just modeling them and the realism will self-assemble. This is why I'm deeply impressed by the game, you often come across realistic behavior that wasnt even directly planned by the devs.
    Real tyres expand too, of course not to that extent where it gets noticeable. But this is the reason why they are always limited to a certain topspeed, far above which they would be torn apart. What is the reason for one set of the Veyrons 400+ kph wheels costing 35.000 euro.

    So what do you mean by exploding? Does the rubber itself (the material) explode or the whole tyre, the shape is torn apart? Maybe its possible to make a use out of it and implement that the tyres get torn apart when you exceed their topspeed, instead of expanding way too much what is not possible in real? --> that would be a limiting factor to expansion
    aand very fun to lose your tyres at 500 kph
  14. -Takedowner22-'s Avatar
    This thing is mysteriously awesome, I don't know why "mysteriously"
  15. pulley999's Avatar
    Quote Originally Posted by Callisto89
    Hey, so there's a speedometer now ? :P
    Also you can't just bind it to the output of the transmission ?
    In the cockpit, he means. They've been there since some of the very early videos. First one here.
    Can't tell if this was before or after the switch to T3D, looks like it might be some very early T3D footage.


    EDIT: He could bind it to the transmission output I think, but that would be cheating, as real cars don't do that. Like he said, real cars compensate in just the same way he added.
  16. garyjpaterson's Avatar
    Quote Originally Posted by gabester
    Although the 25% physics speedup coming in the race update is a big help
    Just wondering how close to this 25% are we going to really see, i mean is that a best case scenario or are multiple hardware configs consistently getting 25% more performance?
  17. thevidmaster's Avatar
    Quote Originally Posted by garypaterso
    Just wondering how close to this 25% are we going to really see, i mean is that a best case scenario or are multiple hardware configs consistently getting 25% more performance?
    that depends on your bottleneck, if its your gpu thats the bottleneck, you will notice little to no fps increase. if your cpu is the bottleneck, you will notice up to a 25% fps increase
  18. Spartacus's Avatar
    Excellent job! This game's getting more realistic as it progresses! Keep up the good work developers!
  19. gabester's Avatar
    Quote Originally Posted by Callisto89
    Hey, so there's a speedometer now ? :P
    Also you can't just bind it to the output of the transmission ?
    There's always been a working speedo. Binding it to the transmission would make zero difference - the wheel expansion has this 2-4% effect on the entire drivetrain Like I said, it also sightly affects gear ratios, in the same way that putting bigger diameter tires on a car would (in addition to making the speedo inaccurate).
  20. TheFrugalLemur's Avatar
    Quote Originally Posted by gabester
    There's always been a working speedo. Binding it to the transmission would make zero difference - the wheel expansion has this 2-4% effect on the entire drivetrain Like I said, it also sightly affects gear ratios, in the same way that putting bigger diameter tires on a car would (in addition to making the speedo inaccurate).
    Are you planning on adding a HUD of any description (Speedo etc.)?
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