“…Given two surfaces , the BS is the set of sphere centers that touch both surfaces at one point each. Due to its stability and geometrical characteristics, the IBS has been used in context retrieval, interaction classification, and functionality analysis ( Zhao et al., 2014 ; Hu et al., 2015 ; Hu et al., 2016 ; Zhao et al., 2016 ; Zhao et al., 2017 ; Ruiz and Mayol-Cuevas, 2020 ). Our approach expands on these ideas and is geometrically intuitive and straightforward.…”