Function compute_involute 

pub fn compute_involute(
    pos_fn: &dyn Fn(f32) -> Vec3,
    tangent_fn: &dyn Fn(f32) -> Vec3,
    t_at_len_fn: &dyn Fn(f32) -> f32,
    total_length: f32,
    start_s: f32,
    steps: usize,
) -> Vec<Vec3>

Involute of a spline: unrolling a string from the curve