Function get_n_points_along_active_track 

fn get_n_points_along_active_track(
    spacings: &[f32],
    segment: Entity,
    idx: f32,
    dir: Dir,
    q_segments: &Query<'_, '_, (Entity, &TrackSegment, &Transform)>,
    q_nodes: &Query<'_, '_, (Entity, &TrackNode)>,
) -> Option<Vec<(Entity, f32, Dir, Vec2)>>

Tries to find and calculate n (length of spacings) points along active track starting at segment and idx, moving along dir.