Function sh_eval_d_impl 

pub fn sh_eval_d_impl<V, const L: usize, const N: usize>(
    t: &ShTable<V, N>,
    x: V,
    y: V,
    z: V,
    out: &mut [V; N],
    ddx: &mut [V; N],
    ddy: &mut [V; N],
    ddz: &mut [V; N],
)
where
    V: FloatVector + CoreMath,

sh_eval_impl plus the ambient Cartesian gradients. The rolled counterpart of sh_d_impl, with the same two-pass structure and gradient semantics.