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Any ideas for how making a flexible border

Discussion in 'Bob's Track Builder' started by asasinuxp, Oct 23, 2010.

  1. Any ideas for how making a flexible border aligned to road?
     
  2. Do you mean a string object and the "align to track" feature? Or do you mean making an object that is flexible when struck?
     
  3. Erwin Greven

    Erwin Greven
    Premium Member

    A tire wall that works like a safer barier would be great.
     
  4. No.The track is not straight,and I found a border(to use in a town),but i cannot align to track because is not flexible(it's a object).
     
  5. You might have more success with a wall. You can change the shape and materials to make it look like the object.
     
  6. Finally,it work's with a wall(after several attempts).
     
  7. Excellent! Glad to hear you worked it out.
     
  8. I've given a lot of thought to this. The best I've been able to come up with is a tire barrier that is not marked as a collision object and then an invisible wall stuck part way inside, so you'd drive into the barrier a short distance before actually getting a collision.

    Wait! I think I've got a great idea on how to make it best work!

    In the properties of objects (or is it just sign objects?), you can hinge it at the bottom, with a spring rate, damper, and mass. So you use two invisible walls, the first one being hinged with a modest mass and high spring rate. The second wall is fixed and constrains the first wall from bending too far and acting like a ramp. Or you could use three walls with the middle one having a heavier mass and spring rate.

    Anyone want to experiment?
     
  9. Erwin Greven

    Erwin Greven
    Premium Member

    I would
     
  10. Looking up tire sidewall spring rates, around 100 lb/in for an uninflated tire. You'd have several springs working in parallel, say 6, that make it 600 lb/in spring rate during a head-on impact as a starting point. A starting point for the mass should be on the order of 800 lbs, since the impacting car is affecting several stacks of tires at once?

    Now you have to convert into SI units... and come up with a damper rate.

    And then start experimenting... probably create several test walls with different spring rates and masses and dampers. Keep them visible so you can watch how they react in the replays. Try some without the second wall and a significantly higher spring rate.

    I took a quick look and there are two likely approaches to testing methodically:
    1) create fresh objects for Xpacker, perhaps labeling them with signs indicating the properties of springrate & mass
    2) just twiddle the values in 3dSimEd

    Questions needing answers:
    a) What differences are seen when struck a glancing blow vs. head-on (glancing blows on real tire barriers 'suck you in' so that it spins the car around)?
    b) What difference does speed have on the impacts?
    c) What differences does mass (NASCAR vs. Lotus 7) & construction of the car (fenders vs. no fenders)?
    d) How critical are the variable values?
    e) When using two walls, how far apart should they be?
    f) How badly are framerates affected?
    g) For a long tire wall, is it better to have several spring walls or one long wall?
     
  11. Aw, nuts... the physical properties of signs, posts, etc. aren't in the object other than specifying what the object should be (sign or post). Instead, they're in the GDB:
    So just set the two walls in place, mark the springy one as a post or sign (whichever makes sense based on whether you have other sign or post objects which you don't want behaving like tire walls) and the other is a normal wall. Then edit the track GDB to try different values.
     
  12. Interesting find about the gdb file there, it's something that has had me baffled for a while now :D

    Also what you can do for this sort of thing is,,
    You can change the values of the tirewall in the .tdf file
    or
    You can add a new entry into the .tdf file, which then corresponds to a material name, all you have to do then is give that material this certain name and it will work however you want it to work.

    The only problem is getting that object to have that material name, from memory I have had problems doing this in the past with XPacker.


    ie,

    ( i haven't changed any values here, you will need to calculate them, this is just an example of what could be done)

    // DEFLATED TIRES
    [FEEDBACK]
    Legal=false Spring=20000.0 Damper=10000.0 CollFrict=0.90 Sparks=0 Scraping=0 WallSkids=1 Sound=tirewall
    Materials=dftwal