Track imperfection from video stabilisation

Discussion in 'Tracks' started by physicsimulation, Aug 19, 2020.

  1. physicsimulation

    physicsimulation New Member

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    Derived from :
    https://assettocorsamods.net/threads/grand-prix-de-trois-rivières-road-layout.2124/

    Imagine you have an onboard camera which use gyroscopic gimble that records stabilizer data.
    You could use these data to infere the road surface imperfection or the vibration sensed by the driver.
    That the subject of this discussion.

    From the refered post, I used video stabilizer software from race track videos to excerpt stabilisation data.
     
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  2. luchian

    luchian Administrator Staff Member

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    Would you like me to copy that post here as well? It will appear as the first post of the thread.
     
  3. physicsimulation

    physicsimulation New Member

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    Here is a video of Michel Brousseau's F1600 on GP3R race track where the camera (with a lot of rolling shutter) was mounted on the car body.
    Stabilized in 2Degree-of-freedom (2DOF, horizontal and vertical)
    https://www.youtube.com/embed/omhEMRW9XE0

    Here is a video of Jean-François Boyte (provincial kart championship winner) on Honda 200cc (open class with 16 HP) where the camera was mounted on his helmet.
    Stabilized in 3DOF (hor, vert, rot) plus lens correction, rendered at twice the real speed.
    https://www.youtube.com/embed/gV-8bbazeIU
    Just use parameters to slow down the speed at 0.5x
     
  4. physicsimulation

    physicsimulation New Member

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    The analysis is based on pixel motion from video that has resolution and frame rate limits.
    Defining a point-of-view (POV) referential determine what kind of vibrations we look at.
    For example, stabilize an helmet ... or stabilize the horizon ... or stabilize the frame body ... or stabilize the tyre's hub, all these are possible POV.

    Repeated from the other post
    ------------------------------------
    Track roughness shakes the tyre patch RLCy connected to wheel hub RLCy connected to the car frame RLCy connected to driver body RLCy connected to the helmet.
    NOTE: RLCy means "resistance, inductance, capacitance", the "y" to create an adverb 8)
    (more useless reading https://www.scielo.br/scielo.php?pid=S1678-58782011000300005&script=sci_arttext&tlng=pt)

    You can attach the cam to the car frame seen a) some horizon (as stabilizer aim) and b) the wheel hub (to get his vibration)
    OR,
    with the same cam position, a) aim some horizon and b) get vibration from the driver's helmet
    OR,
    put the cam onto the driver's helmet and stabilize some horizon to infere the cam vibration.

    Infering track roughness from helmet motion is not direct (see the 4 RCL links) but, if you want to simulate driver seat vibration and/or induced tyre slip/grip, you have more data then nothing.

    Concerning speed and bump, they are frequency related (see graph in the preceding useless reading) and, through 4 RCL links, subject to interpretation.
    Take the Nissan Micra race, these suspensions are too soft and too much unlink helmet-track.
    Take open wheel car and the helmet-track link is more pertinent.
    ----------------------------------

    Data file content :
    Frame number : Frame number of the source video. For interlaced video, the frame number will have an 'A' or 'B' appended, depending on the field.
    Pan X : The number of horizontal panning pixels between (the middle line of) the previous frame and current frame.
    Pan Y : The number of vertical panning pixels between (the middle line of) the previous frame and current frame.
    Rotation : The number of degrees of rotation between (the middle line of) the previous frame and current frame.
    Zoom : The zoom factor between (the middle line of) the previous frame and current frame.
     
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  5. physicsimulation

    physicsimulation New Member

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    As you prefer ...
     
  6. physicsimulation

    physicsimulation New Member

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    Another thing is, most of onboard videos show a pilot that drive in the "quasi-best race line" so you can't expect data from somewhere else.
     
  7. Johnr777

    Johnr777 Moderator

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    I understand the concept, but where's the data? Which software performs this data extraction? Publicly available?
     
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  8. physicsimulation

    physicsimulation New Member

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    The data is not extracted from the Blue, it comes from differential video frame analysis. That's why the result depends on cam resolution and frame speed.
    I am used to work with these video and plugin software (open source).
    On the other side, the software compute but my physicist experience evaluates the meaning and the uncertainty of the results.
    Not recommended for every one.
     
  9. luchian

    luchian Administrator Staff Member

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    Does that mean that you only wanted to share an idea, and not an actual way to do it? :nerd:
     
  10. physicsimulation

    physicsimulation New Member

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    I am ready to share how to do it. I think the preparation is more important then processing video therefore I am opened to help someone to prepare the "experience".

    Targetting meaningfull result need preparation in the video captation and also determine what are the limits of these data is fondamental to the data integration into the ACM engine.
     
  11. Johnr777

    Johnr777 Moderator

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    The way to "integrate" this into AC wont be direct. The data will only serve for comparison or through a 3dsmax or blender script to create a Z axis reference to the track mesh.
     
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  12. physicsimulation

    physicsimulation New Member

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    Process of Dumoulin at GP3R
    Handheld camera
    Near constant slow speed
    Stabilizer aiming as possible to the horizon, clown includes 8(
     
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  13. physicsimulation

    physicsimulation New Member

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    Camera on frame
    Stabilizer aiming the axle
    Oval track, non-radial tyre but no lateral shock absorber
     
    Last edited: Aug 22, 2020
  14. physicsimulation

    physicsimulation New Member

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    Unable to post Isle of Man or F1 or Nissan Micra or Indy Car due to rights infringements on YouTube 8(
     
    Last edited: Aug 22, 2020
  15. physicsimulation

    physicsimulation New Member

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