An algorithm for the geometric reconstruction of knots within timber boards based on fibre angle measurements

•3D fibre angles obtained from laser scanning data exploiting the tracheid effect.•Algorithm for automatic reconstruction of 3D knot geometries within timber boards.•Numerically obtained fibre deviations around knots using a grain-flow analogy.•Complete 3D morphology of timber boards as basis for numerical simulation tools. An algorithm for automatically reconstructing knot geometries within timber boards is presented, which is based on non-destructive fibre angle measurements on the surface, exploiting the tracheid effect, and on an estimate of the pith location. A fast deterministic reconstruction of the geometry for implementation in existing industrial environments is achieved and an adaptive simulated annealing optimisation procedure is employed for higher accuracy. Based thereon, three-dimensional fibre angles are determined numerically and compared to the originally measured data, thereby allowing for a first verification of the procedure. The results can be readily employed for grading purposes and three-dimensional finite element simulations.