Function register 

pub fn register<S>(
    source: &Surface<'_>,
    target: &Surface<'_>,
    search: &S,
    initial: Se3,
    config: &IcpConfig,
) -> IcpResult
where
    S: NeighborSearch + Sync,

Registers source against target.

search must have been built over the target cloud. The returned pose carries source points into the target frame: q ≈ T · p.

The update is left-multiplied, T ← exp(Δξ)·T, so the Jacobian row is [nᵀ | (p' × n)ᵀ] with p' the already-transformed source point. The convention runs through the project: the null spaces of the synthetic scenes and the conditioning analysis assume the same one.