From 54dd0b54484ef4bda4aa31e0c0de92e7ba6f229a Mon Sep 17 00:00:00 2001
From: Richard Brice <37087370+RickBrice@users.noreply.github.com>
Date: Mon, 25 May 2026 10:28:40 -0700
Subject: [PATCH] Fixes bug computing cross slope

---
 src/ifcgeom/mapping/IfcCurveSegment.cpp | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/ifcgeom/mapping/IfcCurveSegment.cpp b/src/ifcgeom/mapping/IfcCurveSegment.cpp
index 1efbed2fe1..6dfd831e6d 100644
--- a/src/ifcgeom/mapping/IfcCurveSegment.cpp
+++ b/src/ifcgeom/mapping/IfcCurveSegment.cpp
@@ -491,11 +491,10 @@ class curve_segment_evaluator {
               // tilt angle in the plane of the cross section
               auto cant = Cant(u);
               auto tilt_angle = start_angle + delta_angle * (cant - start_cant) / delta_cant;
-              Eigen::Vector4d z(0.0, cos(tilt_angle), sin(tilt_angle), 0.0);
+              Eigen::Vector4d axis(0.0, cos(tilt_angle), sin(tilt_angle), 0.0);
 
-              // compute axis direction
-              Eigen::Vector4d y = z.cross3(ref_dir);
-              Eigen::Vector4d axis = ref_dir.cross3(y);
+              // compute cross slope direction
+              Eigen::Vector4d y = axis.cross3(ref_dir);
 
               Eigen::Matrix4d m = Eigen::Matrix4d::Identity();
               m.col(0) = ref_dir;