Meshing: unsigned distance to be able to mesh reach with start_rk > end_rk

src/Meshing/Internal.py

@@ -57,6 +57,13 @@ class InternalMeshing(AMeshingTool):
 
         # we never modify original profiles, we work on the copies
         m_profiles = self.st_to_m(profiles, guide_list)
+
+        # Adapt the spacing to the kilometre-point direction. The value from
+        # the dialog is a distance, so only its magnitude is significant.
+        step = self.signed_step(
+            step, m_profiles[0].rk, m_profiles[-1].rk
+        )
+
         new_profiles = self.interpolate_transversal_step(m_profiles, step)
 
         for new_profiles2 in new_profiles:
@@ -65,6 +72,12 @@ class InternalMeshing(AMeshingTool):
 
         return new_profiles
 
+    @staticmethod
+    def signed_step(step, begin_rk, end_rk):
+        if end_rk < begin_rk:
+            return -abs(step)
+        return abs(step)
+
     def st_to_m(self, profiles, guide_list):
         guide_list = ["un"] + guide_list + ["np"]
         max_values = [0] * (len(guide_list) - 1)