R = VL_RODR(OM) where OM a 3-dimensional column vector computes the Rodrigues' formula of OM, returning the rotation matrix R = expm(vl_hat(OM)).

[R,DR] = VL_RODR(OM) computes also the derivative of the Rodrigues formula. In matrix notation this is the expression

        d(vec expm(vl_hat(OM)) )
dR = ----------------------.
d om^T


[R,DR]=VL_RODR(OM) when OM is a 3xK matrix repeats the operation for each column (or equivalently matrix with 3*K elements). In this case R and DR are arrays with K slices, one per rotation.