(2020-05-20, 7:55)Philippe Hurbain Wrote: As suggested by Owen, it's because of y axis orientation in Ldraw system. You can compensate for that either by modeling upside down, or by using a 180° rotation matrix in stl2dat (-m 0 0 0 1 0 0 0 -1 0 0 0 -1)
This comes from a slightly buggy edge lines / conditonal lines generator of stl2dat. To avoid this, I use the raw mode of stl2dat (-raw) then I generate condlines/edgelins with Edger2 (https://www.philohome.com/isecalc/edger2.htm)
Thank you very much. I'll try. As expected, there are many things to learn^^