Hello, After tedious search through 100s of Scraps I have now isolated the one (SA9.th2) scrap which crashes Therion in extern/poly2tri/sweep/../common/shapes.h It's attached together with an excerpt of the survey data. Admittingly, the walls are not drawn very well, but after fixing and completing the walls (not done in attached sample) it still crashes Therion. May this example be a test case for developers to improve Therion's robustness. BTW, it also crashes older Therion releases. Cheers, Michael. -----Ursprüngliche Nachricht----- Von: Michael [mailto:knollesimage@t-online.de] Gesendet: Samstag, 4. November 2017 14:48 An: 'List for Therion users' <therion@speleo.sk> Betreff: Therion crashes in shapes.h when generating 3D Hello, Seeking advice from Therion developers how to track down the cause of attached crash report, and apply possible workaround. Only happens when generating 3D of any format. Producing plans (pdf, kml) works. I'm running Therion 5.4.1 on Windows 7. The crash seems unrelated to the last scrap processed before the crash, because when I exclude that scrap, it crashes after approx. the same time with a different one. Any help appreciated, Michael.