From cf1552e79e4f80eb431e1e2eae179c1ef30496e5 Mon Sep 17 00:00:00 2001
From: Richard Brice <37087370+RickBrice@users.noreply.github.com>
Date: Fri, 13 Mar 2026 11:16:10 -0700
Subject: [PATCH] Simplifies IfxAxis2PlacementLinear, assumes default Axis =
 (0,0,1)

---
 .../mapping/IfcAxis2PlacementLinear.cpp       | 45 +++----------------
 1 file changed, 6 insertions(+), 39 deletions(-)

diff --git a/src/ifcgeom/mapping/IfcAxis2PlacementLinear.cpp b/src/ifcgeom/mapping/IfcAxis2PlacementLinear.cpp
index b11b61b46b..f86f59ac98 100644
--- a/src/ifcgeom/mapping/IfcAxis2PlacementLinear.cpp
+++ b/src/ifcgeom/mapping/IfcAxis2PlacementLinear.cpp
@@ -29,10 +29,8 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcAxis2PlacementLinear* inst)
         Logger::Error(std::runtime_error("Location must be IfcPointByDistanceExpression for IfcAxis2PlacementLinear"));
     }
 
-    Eigen::Vector3d o, axis(0, 0, 1), refDirection;
-
     taxonomy::matrix4::ptr m = taxonomy::cast<taxonomy::matrix4>(map(inst->Location()));
-    o = m->components().col(3).head<3>();
+    Eigen::Vector3d o = m->components().col(3).head<3>();
 
     // From 8.9.3.4 IfcAxis2PlacementLinear there are 4 cases that need to be considered
     // 1) Axis is given but not RefDirection
@@ -40,43 +38,12 @@ taxonomy::ptr mapping::map_impl(const IfcSchema::IfcAxis2PlacementLinear* inst)
     // 3) Neither Axis or RefDirection are provided
     // 4) Both Axis and RefDirection are provided
 
-    const bool hasAxis = inst->Axis() != nullptr;
-    const bool hasRef = inst->RefDirection() != nullptr;
+    Eigen::Vector3d z = inst->Axis() ? *taxonomy::cast<taxonomy::direction3>(map(inst->Axis()))->components_ : Eigen::Vector3d(0,0,1); // Axis is (0,0,1) when omitted
+    Eigen::Vector3d rd = inst->RefDirection() ? *taxonomy::cast<taxonomy::direction3>(map(inst->RefDirection()))->components_ : m->components().col(0).head<3>(); // RefDirection is the curve tangent when omitted
+    Eigen::Vector3d y = z.cross(rd);
+    Eigen::Vector3d x = y.cross(z);
 
-    /*
-    if (hasAxis != hasRef) {
-		Logger::Warning("Axis and RefDirection should be specified together", inst);
-	}
-	*/
-
-    if (hasAxis && !hasRef) {
-        taxonomy::direction3::ptr a = taxonomy::cast<taxonomy::direction3>(map(inst->Axis()));
-        axis = *a->components_;
-
-        refDirection = m->components().col(0).head<3>(); // RefDirection is the curve tangent when omitted
-        // refDirection is not necessarily orthogonal to axis.
-        // axis.cross(refDirection) gives y. y.cross(axis) gives x=refDirection
-        refDirection = axis.cross(refDirection).cross(axis);
-    } 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));
-    } 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));
-    } else {
-        taxonomy::direction3::ptr a = taxonomy::cast<taxonomy::direction3>(map(inst->Axis()));
-        axis = *a->components_;
-
-        taxonomy::direction3::ptr r = taxonomy::cast<taxonomy::direction3>(map(inst->RefDirection()));
-        refDirection = *r->components_;
-        refDirection = axis.cross(refDirection).cross(axis); // refDirection needs to be orthogonal to axis
-    }
-
-    // axis and refDirection need to be orthogonal
-    return taxonomy::make<taxonomy::matrix4>(o, axis, refDirection);
+    return taxonomy::make<taxonomy::matrix4>(o, z, x);
 }
 
 #endif