1. #1
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  2. #2
    This no bug, these low-rida mod fo' sho'

    BTW, how did you get your hands onto this beta version of "Grand Theft Tempest", huh?
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  3. #3
    pdog1's Avatar Senior Member
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    Aw man you needed the song Low Rider to make that video.
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  4. #4
    Hawgdog's Avatar Senior Member
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    Originally posted by pdog1:
    Aw man you needed the song Low Rider to make that video.
    Arent' you the one who did the vid with Pe-8 rolls better than jug/tiger go boom?
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  5. #5
    VW-IceFire's Avatar Senior Member
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    Originally posted by Hawgdog:
    click here for short vid of bug
    I don't know how you do it yet...

    I have gotten the tail wheel stuck in the ground on a particularly nasty landing mind you.
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  6. #6
    pourshot's Avatar Senior Member
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    LOL
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  7. #7
    Funny to watch, yet not a uncommon sight.

    Saw Ki46 recces bounce on the runway just yesterday. Would regard this a strange FM issue, maybe some sort of land contact screwup ingame.

    S!
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  8. #8
    Viper2005_'s Avatar Senior Member
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    What frame rate was the original track recorded at?

    X-Plane suffers from similar problems at low frame rates. It does this because it works by integrating accelerations over the interval between frames to generate angular and linear velocities. To simplify this process it just multiplies the acceleration by the time interval between frames to produce a velocity, an assumption which works well if the gap between frames is small.

    This means that small accelerations associated with rounding errors, combined with big gaps between frames can result in appreciable velocities. These appreciable velocities produce an appreciable restorative force, which leads to an appreciable restorative acceleration. Throw in another big gap between frames and the cycle repeats.

    You're especially likely to get this behaviour with ground handling because the ground is very stiff; if the wheels are half an inch off the ground there's no force. As soon as they touch it there's a considerable force; this means that considerable acceleration gradients are present. Lots of jerk and jounce means that the errors associated with numerical integration over the frame interval are larger. With poor frame rates it was possible for the bouncing to get so bad that some aeroplanes would actually destroy themselves when they spawned in, especially if it had an unusual configuration (aka the wrong number of wheels). This problem was made worse by the fact that X-Plane tends to drop aeroplanes onto the ground from a couple of feet when they spawn in (presumable to ensure that they don't get stuck on the wrong side of it!).

    I wouldn't be surprised if IL2 is suffering from a similar problem.

    One work around is to hard code considerable energy loss into the gear. So you'd calculate the kinetic energy associated with landing gear impact, and cap the kinetic energy associated with the restorative acceleration at some small fraction of the input energy (say 70% or so).

    This effectively forces the sim to damp out vibrations associated with the landing gear even if the frame rates are awful.

    However, the real solution is to run at high frame rates.
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  9. #9
    Hawgdog's Avatar Senior Member
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    QMB, ran a mission with crappy weather, and four tempests. We landed
    I shot my guns for a moment, and the plane next to me started hopping.
    Within moments all planes were hopping, including mine.
    I've tracks of C-47's and I-16's hopping as well under the same condidtions
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  10. #10
    Originally posted by Viper2005_:
    What frame rate was the original track recorded at?

    X-Plane suffers from similar problems at low frame rates. It does this because it works by integrating accelerations over the interval between frames to generate angular and linear velocities. To simplify this process it just multiplies the acceleration by the time interval between frames to produce a velocity, an assumption which works well if the gap between frames is small.

    This means that small accelerations associated with rounding errors, combined with big gaps between frames can result in appreciable velocities. These appreciable velocities produce an appreciable restorative force, which leads to an appreciable restorative acceleration. Throw in another big gap between frames and the cycle repeats.

    You're especially likely to get this behaviour with ground handling because the ground is very stiff; if the wheels are half an inch off the ground there's no force. As soon as they touch it there's a considerable force; this means that considerable acceleration gradients are present. Lots of jerk and jounce means that the errors associated with numerical integration over the frame interval are larger. With poor frame rates it was possible for the bouncing to get so bad that some aeroplanes would actually destroy themselves when they spawned in, especially if it had an unusual configuration (aka the wrong number of wheels). This problem was made worse by the fact that X-Plane tends to drop aeroplanes onto the ground from a couple of feet when they spawn in (presumable to ensure that they don't get stuck on the wrong side of it!).

    I wouldn't be surprised if IL2 is suffering from a similar problem.

    One work around is to hard code considerable energy loss into the gear. So you'd calculate the kinetic energy associated with landing gear impact, and cap the kinetic energy associated with the restorative acceleration at some small fraction of the input energy (say 70% or so).

    This effectively forces the sim to damp out vibrations associated with the landing gear even if the frame rates are awful.

    However, the real solution is to run at high frame rates.
    I would be very surprised if IL2 had this problem. There are integrators much more precise than simple euler oens that avoid such problems. No AAA level game uses a simple euler integrator.
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