tyre-squeal.gd

# This is the tyre squeal model from this clip: https://youtu.be/Likwgc5s_T0
# You need an "AudioStreamPlayer3D" at the position of each wheel, and then run
# this function from _process_physics, with each wheel node passed
  
  func tyre_squeal(tyre):
    # increase squeal amplitude with road speed
    var speed_factor = 1
    if (get_speed_kph() < 100):
      speed_factor = 0.5 + 0.5 * (get_speed_kph()/100)

    # increase squeal amplitude with a guess at the weight on this corner...
    var SUSP_MIN = 0.08
    var SUSP_MAX = 0.10
    var susp_pos = (tyre.translation.y - SUSP_MIN) / (SUSP_MAX - SUSP_MIN)
    var squeal_rate = clamp(susp_pos, 0.0, 1.0) * slip_ratio * speed_factor

    var audio_node = tyre.get_node("AudioStreamPlayer3D")
    var old_db = audio_node.unit_db
    var new_db = -80
    if (squeal_rate > 0.01):
      if (!audio_node.playing):
        audio_node.playing = true
      audio_node.pitch_scale = 1.1 - squeal_rate * 0.6
      new_db = 10*log(squeal_rate) # note log(squeal_rate) is always negative
    else:
      audio_node.playing = true
    audio_node.unit_db = old_db * 0.95 + new_db * 0.05