**User story :**\ As Tympan user, I want to be able to create screen with numerous edges, in order to be able to **Steps to reproduce behaviour :** - open Tympan - open[model.xml](/uploads/9215a0828267303c3cead22e963eb050/model.xml) - Launch acoustic computation - it fails with this error message : Error: Problème avec la surface Site 0->Infrastructure 0->Construction 14->Ecran mince 13-> :Face can not be triangulated (invalid plane?) => KO **Acceptance criteria :** - analysis docmented in this issue - fix problem - acoustic computation succeeds on the model attached to this issue