From 0ec895f1a39322a92c006fe7b320944772e493bc Mon Sep 17 00:00:00 2001
From: Richard Brice <37087370+RickBrice@users.noreply.github.com>
Date: Fri, 29 May 2026 15:11:07 -0700
Subject: [PATCH] uses axis direction from curve evaluation when Axis is not
 provided

---
 src/ifcgeom/mapping/IfcAxis2PlacementLinear.cpp | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/ifcgeom/mapping/IfcAxis2PlacementLinear.cpp b/src/ifcgeom/mapping/IfcAxis2PlacementLinear.cpp
index b11b61b46b..836a6391f8 100644
--- a/src/ifcgeom/mapping/IfcAxis2PlacementLinear.cpp
+++ b/src/ifcgeom/mapping/IfcAxis2PlacementLinear.cpp
@@ -60,12 +60,10 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcAxis2PlacementLinear* inst)
     } else if (!hasAxis && hasRef) {
         taxonomy::direction3::ptr r = taxonomy::cast<taxonomy::direction3>(map(inst->RefDirection()));
         refDirection = *r->components_;
-        Eigen::Vector3d up(0, 0, 1);
-        axis = refDirection.cross(up.cross(refDirection));
+        axis = m->components().col(2).head<3>(); // Axis is the curve normal when omitted
     } else if (!hasAxis && !hasRef) {
         refDirection = m->components().col(0).head<3>(); // RefDirection is the curve tangent when omitted
-        Eigen::Vector3d up(0, 0, 1);
-        axis = refDirection.cross(up.cross(refDirection));
+        axis = m->components().col(2).head<3>(); // Axis is the curve normal when omitted
     } else {
         taxonomy::direction3::ptr a = taxonomy::cast<taxonomy::direction3>(map(inst->Axis()));
         axis = *a->components_;