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Outward drifting vehicles gradually reach a lower speed while drifting

Discussion in 'General Discussion' started by Mister Wu, Jul 4, 2016.

  1. Mister Wu

    Mister Wu

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    Just a small thing I noticed while I was testing the angular velocity of outward and inward drifting vehicles, mostly relevant for the 200cc class.


    When looking at the trails left by the wheels in the icy part of GCN Sherbet Land, it can be noticed that outward drifting vehicles form a spiraling trail that gradually narrows until it becomes a circle, while inward drifting vehicles form a circle, with a little indentation in the point where the Super Mini-Turbo is charged.


    To understand what the origin of the spiraling trail was, the angular velocity while the trail was still a spiral was measured. The reason is simple: when going in a circular path, the radius of curvature, r, can be expressed as v / ω, where ω is the angular velocity while v is the speed of the vehicle. If a spiral trail whose radius decreases over time is formed, it means that either angular velocity is increasing or the speed of the vehicle is decreasing.
    The test is the following:


    And as a reference point a small polygonal shape in the ice was used:
    D2.jpg
    In this image the shape used as reference is right behind the rear wheel.

    The resulting time needed to reach that shape again was measured in four consecutive circles, the first one starting from the first time the shape was met, on frame 5492 of the video. Here are the measured times:

    1st circle: 245 frames
    2nd circle: 245 frames
    3rd circle: 246 frames
    4th circle: 245 frames

    Therefore, the angular velocity isn't significantly affected, meaning that the reason why the the spiraling trails are formed is that outward drifting vehicles gradually reach a lower speed while drifting.
    It's important to point out that this doesn't happen with inward drifting bikes, meaning that they don't gradually reach a lower speed while drifting. Indeed, angular velocity was measured also in the case of inward drifting bikes using as refrence point the frame where the ice tower on the left of the ice arc disappeared.
    DRef2.png
    The reference point for inward drifting bikes.

    The resulting time needed to reach that reference point was measured in four consecutive circles, the first one being measured from the first time the reference point was met, on frame 13342 of the video (shown above to illustrate the reference point). Here are the measured times:

    1st circle: 263 frames
    2nd circle: 262 frames
    3rd circle: 263 frames
    4th circle: 263 frames

    Therefore, angular velocity doesn't change with time also with inward drifting vehicles. Since the trails left by the wheels form circles, the radius of curvature doesn't change as well and as a consequence, the speed of the bikes stays constant when they drift.

    Finally, a last interesting aspect was studied: what happens when the outward drifting vehicles start drifting with a speed lower than the lowest speed reached when drifting? This video clarifies what happens:


    Simply put, the outward drifting vehicle gradually accelerates until it reaches this lowest speed while drifting, meaning that this lowest speed acts as an asymptote and makes the vehicle reach a lower top speed than the one it would reach if it was going straight and it was not drifting.

    So, as take-home message, outward drifting vehicles gradually reach a lower speed while drifting, while inward drifting bikes maintain their speed while drifting.
    Furthermore, this lower speed while drifting acts as top speed for the vehicles that are drifting while still accelerating, causing them to reach a lower top speed than the one they would reach if they were going straight and weren't drifting.

    MODEL BASED ON RESULTS OF NEW EXPERIMENTS

    With new experiments performed, it was possible to create a new model to explain what happens when drifting:

    When starting with a sharp drift from top speed (i.e. when tilting the control stick or pressing the directional buttons in the direction of the turn), the vehicle quckly loses speed; judging by the traisl left by inward drifting bikes, this loss seems to fully happen even before the Super Mini-Turbo is charged, so before 2 seconds have passed. This loss is:

    around 2% of top speed for 45° softdrifts (those obtained with the D-Pad)
    around 8% of top speed for sharpest drifts

    furthermore, after reaching this lower speed, outward drifting vehicles gradually lose an additional amount of speed:

    around 1% of top speed for 45° softdrifts (those obtained with the D-Pad)
    around 4% of top speed for sharpest drifts

    when starting with a neutral or widened drift from top speed, the vehicle doesn't lose any amount of speed.
    However, if from that situation the drift is sharpened (i.e. the player is tilting the control stick or pressing the directional buttons in the direction of the turn), the vehicle gradually reaches the minimum speed corresponding to the drifting angle (e.g. with sharpest drifts, 92% of top speed for inward drifting bikes and 88% of top speed for outward drifting vehicles). Inward drifting bikes reach this minimum speed a little earlier than outward drifting vehicles, but due to the higher speed while drifting this doesn't necessarily result in a quicker speed loss in the case of inward drifting bikes.
     
    Last edited: May 7, 2017
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  2. Sarantis

    Sarantis

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    Awesome! I'm glad Indrift bikes have AT LEAST a minor advantage over outdrift vehicles when it comes to speed, speed boosts, etc.!
     
  3. Plexy

    Plexy

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    Bumping old thread...

    Anyways, can softdrifting prevent this in any way? Seems possible because it allows you to start a drift faster, so you should be able to lose less speed.
     
  4. Mister Wu

    Mister Wu

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    Thanks for the interest!
    You can see the GamePad D-Pad softdrifting case at 2:18 in the second video ("MK8 - A possible explanation for the spiral trails when using outward drifting vehicles"). The spiral trail is still present, although the effect is less pronounced. This apparently indicates that with outward drifting vehicles, the speed reached while drifting for long times depends on how sharp the drift is - the sharper the drift, the lower the speed reached.

    If we consider this loss of speed alone, with oD vehicles one should release the Mini-Turbo/Super Mini Turbo as soon as possible so that the drift lasts as little as possible and not much speed is lost. Softdrifting would help in this as well, as the MT is charged with the same speed as the sharpest drifts, allowing to release the MT and SMT sooner.

    So, as a tl;dr, with oD vehicles softdrifting makes this effect less pronounced and even allows a faster release of MTs and SMTs without enforcing sharp drifts, but doesn't prevent it completely - it's always there unless an iD bike is used.

    An interesting consequence, though: when accelerating with an oD vehicle, softdrifting is definitely recommended as it leads to a less penalizing lower speed while drifting, which acts pretty much as a speed cap for the vehicle that is drifting while still accelerating.
     
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  5. Plexy

    Plexy

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    Interesting. Thanks for clarifying.:)
     
  6. Rhodechill2

    Rhodechill2

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    How long tdo they ave to drift before losing speed? Lie, how long is it safe to hold a SMT/MT in time trial?



    What ice tower/ice arc?
     
  7. Mister Wu

    Mister Wu

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    Thanks for the question, I made some additional experiments about the speed loss while drifting and here are the results in % of top speed (D-Pad softdrifts are softdrifts in the direction of the turn with up and the direction of the turn on the GamePad's D-Pad, in this case mostly right):
    {EDIT: I had to remake the experiemnts, as the 3% to 4% speed loss, which is a 5% to 7% speed loss when considring the actual speed at which I was testing, is the speed loss of the Mushroom Boost which i was using to start the dirfts, I found another method to start them that doesn't have such a huge speed loss)

    NEUTRAL AND WIDENED DRIFTS: 0 to 2% of top speed, the method I'm using makes it very difficult to precisely determine this amount, but it seems always greater than 0%
    D-PAD SOFTDRIFTS with iD bikes: 1.27% which is actually 2% of top speed, reached around 8 seconds after sharpening the drift
    SHARPEST DRIFTS WITH iD BIKES: 4.93%, which is actually 8% of top speed, reached around 8 seconds after sharpening the drift
    D-PAD SOFTDRIFTS with oD BIKES (and oD vehicles in general, as you can see above): 1.86%, which is actually 3% of top speed, reached around 9 seconds after sharpening the drift
    SHARPEST DRIFTS WITH oD BIKES: 7.44%, which is actually 12% of top speed, reached around 14 seconds after sharpening the drift

    Essentially, softdrifting has a modest speed loss when compared to the sharpest drifting, which has around 4 times the speed loss. Inward drifting bikes are effectively faster when drifting in both conditions, with a 1% of top speed advantage while softdrifting that becomes a 4% advantage when drifting sharply. Surprisingly, when starting from a wide drift, even inward drifting bikes reach the lower speed slowly, although apparently not as slowly as oD vehicles.
    The arc is the one in the screenshot above, the ice towers are those tall ice buildings that can be seen also on the left of this arc when using the screenshot above as reference point (I was drifting toward the right).
     
    Last edited: Apr 25, 2017
  8. Mister Wu

    Mister Wu

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    Sorry for double posting, but I had discovered that the method I used was flawed and couldn't determine the actual speed loss while softdrifting. I therefore measured that and the speed loss while drifting sharply with higher precision, reaching slightly different conclusions, although iD bikes are still faster when drifting.
     
  9. Rhodechill2

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    You never answered my main questions:

    How long tdo they have to drift before losing ANY speed? Lie, how long is it safe to hold a SMT/MT in time trial?





    you say "1.27% which is actually 2%" why the different values? 1.27 = actual slowdown from drift speed but 2% = slowdown from top speed?

    inward drifting bikes reach the lower speed slowly, although apparently not as slowly as oD vehicles

    ^so thats bad, right, for iD? because the OD bikes take LONGER TO SLOW which means higher speed after less time passes?

    And if you say it takes, say, 8 secondss after drift, the slowdown is gradual for the 8 seconds right? or is it abrupt?




    nts just as q's not go crazy at all not even close
     
  10. Mister Wu

    Mister Wu

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    Without a speedometer it's pretty much impossible to reconstruct how the loss of speed goes, only how fast a certain final speed is reached, anyway it should start immediately as you land.

    1,27% of tops speed in normal roads, the top speed in the section tested was way lower (little more than 55%), so you have to take this into consideration.
    First of all, these results apply when you start from a wide drift, secondly, iD bikes still have an higher final speed while drifting, so even if they reach it a bit more quickly, this is not as dramatic as it sounds.
    The slowdown is gradual, not abrupt.
     
  11. Mister Wu

    Mister Wu

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    Sorry for the double post, but I added to the main post a model which should explain the results of both experiments, without a speedometer I don't know how if I will be able to discover more about this curious mechanics.

    EDIT: ok, some new experiments suggest that the initial loss of speed too is gradual and not really abrupt, so changing that part.
     
    Last edited: May 7, 2017
  12. Rhodechill2

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    "Without a speedometer it's pretty much impossible to reconstruct how the loss of speed goes"

    ..well I thought that was the whoel point of the spiral test. Anyway, what starts 'immediately as you land'?

    "1,27% of tops speed in normal roads, the top speed in the section tested was way lower (little more than 55%), so you have to take this into consideration." Well whats the 1.27 for as opposed to the 2? why the diff values?

    " iD bikes still have an higher final speed while drifting"
    Really? All?

    "The slowdown is gradual, not abrupt."

    so does the gradual process begin 8 seconds in, or right away?
     
  13. Mister Wu

    Mister Wu

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    I'm sorry, but no indirect test can be as informative as a digital speedometer, which is why I keep asking Nintendo to reintroduce it. Anyway, judging by the various experiments, the loss of speed starts pretty much immediately after landing and is gradual: the speed gradually decreases until it reaches a lower value, which is a fraction of the current top speed. I said "current top speed" because in some particular areas, called by Nintendo "DIRT", "ICE" and "SAND", the max speed is a fraction of the max speed on normal roads, said fraction is actually the BrakeRt in-game stat. You need to take this into account when calculating the fraction of the current top speed: a loss of 1% of the top speed in normal roads on an area that has a BrakeRt of 0.3 is a loss of around 3.3% of the current maximum speed, for example.
    Finally, all iD bikes have this feature, as you can see from their different trails left on the icy parts of GCN Sherbet Land.
    Of course, we're talking about relative speed loss, it's not like Lemmy + Sport Bike + Leaf Tires with 0 coins is faster than Morton + Circuit Special + Slick Tires with 10 coins when both of them are drifting sharply, the speed advantage of Morton is still there, it's just less than the speed advantage when going straight at full speed, thanks to this bonus.
     
  14. Rhodechill2

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    BrakeRt in-game stat

    What's that?

    thanks to this bonus.

    What bonus?

    "called by Nintendo "DIRT", "ICE" and "SAND"

    Where do they officially call it this?

    "1,27% of tops speed in normal roads, the top speed in the section tested was way lower (little more than 55%), so you have to take this into consideration." Well whats the 1.27 for as opposed to the 2? why the diff values?
     
  15. Mister Wu

    Mister Wu

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    Those names were first revealed in the statistics files of Mario Kart 7 (you can see the table of offroad statistics here, click on OffRoad and you'll see it). Mario Kart 8 reused the offroad statistics' table, channging the numerical values (you can see the updated MK8 table here, click on PROF).

    BrakeRt is the relative maximum speed on various types of terrain, so the fraction of the maximum speed in said terrain to the maximum speed in normal roads.

    The bonus is the lower speed penalty while drifting more sharply than in neutral drifts.

    That's because BrakeRt, the relative maximum speed, in that terrain was little more than 0.55; 1.27 / 0.55 ≈ 2%
     
  16. Rhodechill2

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    Why did you test speed loss in the ice section for the 1.27 -> 2% value? Why not on regular road?
     
  17. Mister Wu

    Mister Wu

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    There isn't a BrakeRt for regular road, the max speed on it is always the one set in the speed stats, and due to the lack of a speedometer the only thing you can use to know how much speed you losed is seeing the transition from drifting to inability to drift - signaled by smoke coming out of the exhaust pipes. This transition happens when the current speed is less than 55% of the top speed. So, knowing the maximum speed on that terrain - determined by the SlipRt stat - and whether or not the transition from drifting to inability to drift happens, you can determine with various tries how much speed is lost while drifting.
     

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