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 watershed lines. The interest of this approach is that its restriction to profiles leads to the same motif notion as in the standardised method. Catchment basins are determined using an algorithm simulating global surface immersion, 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 motif combination process used, which never requires the direct combination of adjacent motifs. This guarantees the stability and uniqueness of the solution. After a theoretical overview of the method, results obtained from various 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.