Watershed lines and catchment basins: a new 3D-motif method

This article presents a 3D extension of the motif method (ISO 12085), where 3D-motifs are defined as the catchment basins of a surface, separated by w atershed lines. The interest of this approach is that its restriction to pr ofiles leads to the same motif notion as in the standardised method. Catchm ent basins are determined using an algorithm simulating global surface imme rsion, They are progressively combined to perform a multiscale analysis of surface features and extract all the significant motif sets, from roughness to waviness. The originality of the proposed method lies in the indirect m otif combination process used, which never requires the direct combination of adjacent motifs. This guarantees the stability and uniqueness of the sol ution. After a theoretical overview of the method, results obtained from va rious engineering surfaces are presented and new statistical parameters for surface characterisation, calculated from 3D-motifs are proposed. (C) 2000 Elsevier Science Ltd. All rights reserved.