From 8a739ad5b77e874035a82e8881406bcb1eeedf4a Mon Sep 17 00:00:00 2001
From: Furgo <148809153+furgo16@users.noreply.github.com>
Date: Wed, 14 Jan 2026 15:42:05 +0100
Subject: [PATCH] BIM: provide better user information when a face
 horizontality or verticality cannot be determined (#26231)

* BIM: pinpoint failing face for ArchComponent.isVertical()

* BIM: pass face index when checking for verticality

* BIM: keep old comment

Co-authored-by: Roy-043 <70520633+Roy-043@users.noreply.github.com>

---------

Co-authored-by: Roy-043 <70520633+Roy-043@users.noreply.github.com>
---
 src/Mod/BIM/ArchComponent.py | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/src/Mod/BIM/ArchComponent.py b/src/Mod/BIM/ArchComponent.py
index f753ba3934..961c91bae0 100644
--- a/src/Mod/BIM/ArchComponent.py
+++ b/src/Mod/BIM/ArchComponent.py
@@ -1341,13 +1341,21 @@ class AreaCalculator:
         for prop in ["VerticalArea", "HorizontalArea", "PerimeterLength"]:
             setattr(self.obj, prop, 0)
 
-    def isFaceVertical(self, face):
+    def isFaceVertical(self, face, face_index=None):
         """Determine if a face is vertical.
 
         A face is considered vertical if:
         - Its normal vector forms an angle close to 90 degrees with the Z-axis.
         - The projected face has an area of zero.
 
+        Parameters
+        ----------
+        face : Part.Face
+            The face object to be checked.
+        face_index : str, optional
+            The face's 1-based index identifier, used for debugging error messages.
+            Defaults to None.
+
         Notes
         -----
         The check whether the projected face has an area of zero means that roof-like
@@ -1360,6 +1368,8 @@ class AreaCalculator:
         import DraftGeomUtils
         import TechDraw
 
+        face_name = f" Face{face_index}" if face_index is not None else ""
+
         if face.Surface.TypeId == "Part::GeomCylinder":
             angle = face.Surface.Axis.getAngle(FreeCAD.Vector(0, 0, 1))
             return self.isZeroAngle(angle)
@@ -1380,7 +1390,7 @@ class AreaCalculator:
                     projectedArea = Part.Face(wires).Area
             except Part.OCCError:
                 FreeCAD.Console.PrintWarning(
-                    translate("Arch", f"Could not project face from {self.obj.Label}\n")
+                    translate("Arch", f"Could not project face{face_name} from {self.obj.Label}\n")
                 )
                 return False
 
@@ -1391,7 +1401,7 @@ class AreaCalculator:
             FreeCAD.Console.PrintWarning(
                 translate(
                     "Arch",
-                    f"Could not determine if a face from {self.obj.Label}"
+                    f"Could not determine if face{face_name} from {self.obj.Label}"
                     " is vertical: normalAt() failed\n",
                 )
             )
@@ -1429,8 +1439,8 @@ class AreaCalculator:
         horizontalAreaFaces = []
 
         # Compute vertical area and collect faces to be projected for the horizontal area
-        for face in self.obj.Shape.Faces:
-            if self.isFaceVertical(face):
+        for i, face in enumerate(self.obj.Shape.Faces, start=1):
+            if self.isFaceVertical(face, face_index=i):
                 verticalArea += face.Area
             else:
                 horizontalAreaFaces.append(face)