DT (Delta Time) Quiz

00_result.md

End result if done correctly:

D491FC6E-A5EB-4C5F-9AE9-EAADCCA7F984.MP4

main.rb

# QUIZ/CHALLENGE: add the multiplcation of dt (delta_time) to the 
# correct lines in these three functions to see if you really understand
# the nuances of delta_time

def calc_car dt = 1
  target_speed = if state.engine == :high
                   state.high_speed
                 else
                   state.low_speed
                 end

  state.speed *= 0.98 if steering_at_limit?

  if auto_break?
    state.speed *= state.auto_break_speed_degredation
  else
    ds = target_speed - state.speed
    state.speed += ds * state.acceleration_deceleration_ratio
  end

  state.speed = state.min_speed if state.speed < state.min_speed

  velocity_x     = state.speed * Math.sin(state.angle_r + state.steer_angle_r) * (1.0 - state.drift_percentage_right - state.drift_percentage_left)
  velocity_y     = state.speed * Math.cos(state.angle_r + state.steer_angle_r) * (1.0 - state.drift_percentage_right - state.drift_percentage_left)

  normal_x_right = state.speed * Math.sin((PI / 2.0 ) - state.angle_r) * state.drift_percentage_right
  normal_y_right = state.speed * Math.cos((PI / 2.0 ) - state.angle_r) * state.drift_percentage_right * -1.0

  normal_x_left  = state.speed * Math.sin((PI / 2.0 ) - state.angle_r) * state.drift_percentage_left * -1.0
  normal_y_left  = state.speed * Math.cos((PI / 2.0 ) - state.angle_r) * state.drift_percentage_left

  state.x       += (velocity_x + normal_x_right + normal_x_left)
  state.y       += (velocity_y + normal_y_right + normal_y_left)

  state.angle_r -= state.steer_angle_r
end

def calc_physics dt = 1
  if drift_mode?
    if    state.steer_angle_r > 0
      state.drift_percentage_right *= state.momentum_toward_normal
      state.drift_percentage_left  *= state.momentum_away_from_normal
    elsif state.steer_angle_r < 0
      state.drift_percentage_right *= state.momentum_away_from_normal
      state.drift_percentage_left  *= state.momentum_toward_normal
    else
      state.drift_percentage_right *= state.momentum_decay_out_of_drift
      state.drift_percentage_left  *= state.momentum_decay_out_of_drift
    end
  else
    state.drift_percentage_right   *= state.momentum_decay_out_of_drift
    state.drift_percentage_left    *= state.momentum_decay_out_of_drift
  end

  state.drift_percentage_right  = state.drift_minimum if drift_mode? && state.drift_percentage_right < state.drift_minimum
  state.drift_percentage_left   = state.drift_minimum if drift_mode? && state.drift_percentage_left  < state.drift_minimum

  state.drift_percentage_right  = state.drift_maximum if state.drift_percentage_right > state.drift_maximum
  state.drift_percentage_left   = state.drift_maximum if state.drift_percentage_left  > state.drift_maximum

  state.drift_percentage_right  = state.drift_percentage_right.round(4)
  state.drift_percentage_left   = state.drift_percentage_left.round(4)
end

def calc_steering dt = 1
  steer_speed = steering_wheel_delta * state.turn_magnitude.abs

  # steering improves when auto breaking
  if auto_break?
    steer_speed *= 3.0
    state.auto_break_at = state.clock
  end

  # outputs.debug << { x: 30, y: 30, text: "steer angle: #{state.steer_angle_r}", r: 255, g: 255, b: 255 }
  # outputs.debug << { x: 30, y: 60, text: "steer range: #{state.steering_wheel_range}", r: 255, g: 255, b: 255 }
  # outputs.debug << { x: 30, y: 90, text: "steer speed: #{steer_speed}", r: 255, g: 255, b: 255 }
  case state.steering
  when :right
    if state.steer_angle_r > state.steering_wheel_range * -1.0
      state.steer_angle_r -= steer_speed
    end
  when :left
    if state.steer_angle_r < state.steering_wheel_range
      state.steer_angle_r += steer_speed
    end
  when :released
    if !drift_mode?
      if state.steer_angle_r < 0
        state.steer_angle_r += steering_wheel_delta * state.steering_wheel_reset_perc
      elsif state.steer_angle_r > 0
        state.steer_angle_r -= steering_wheel_delta * state.steering_wheel_reset_perc
      end
    end
  end

  state.steer_angle_r = state.steer_angle_r.round(4).to_f
end