Added mirror factors to .3mf import and enabled import factors

src/libslic3r/Format/3mf.cpp

@@ -1249,14 +1249,25 @@ namespace Slic3r {
 
     void _3MF_Importer::_apply_transform(ModelInstance& instance, const Transform3d& transform)
     {
-        // slic3r ModelInstance cannot be transformed using a matrix
-        // we extract from the given matrix only the values currently used
-
         // translation
         Vec3d offset = transform.matrix().block(0, 3, 3, 1);
 
-        // scale
         Eigen::Matrix<double, 3, 3, Eigen::DontAlign> m3x3 = transform.matrix().block(0, 0, 3, 3);
+#if ENABLE_MIRROR
+        // mirror
+        // it is impossible to reconstruct the original mirroring factors from a matrix,
+        // we can only detect if the matrix contains a left handed reference system
+        // in which case we reorient it back to right handed by mirroring the x axis
+        Vec3d mirror = Vec3d::Ones();
+        if (m3x3.col(0).dot(m3x3.col(1).cross(m3x3.col(2))) < 0.0)
+        {
+            mirror(0) = -1.0;
+            // remove mirror
+            m3x3.col(0) *= -1.0;
+        }
+
+        // scale
+#endif // ENABLE_MIRROR
         Vec3d scale(m3x3.col(0).norm(), m3x3.col(1).norm(), m3x3.col(2).norm());
 
         // invalid scale value, return
@@ -1273,6 +1284,9 @@ namespace Slic3r {
         instance.set_offset(offset);
         instance.set_scaling_factor(scale);
         instance.set_rotation(rotation);
+#if ENABLE_MIRROR
+        instance.set_mirror(mirror);
+#endif // ENABLE_MIRROR
     }
 
     bool _3MF_Importer::_handle_start_config(const char** attributes, unsigned int num_attributes)

src/libslic3r/Model.cpp

@@ -711,9 +711,13 @@ void ModelObject::center_around_origin()
 
     if (!this->instances.empty()) {
         for (ModelInstance *i : this->instances) {
+#if ENABLE_MIRROR
+            i->set_offset(i->get_offset() - shift);
+#else
             // apply rotation and scaling to vector as well before translating instance,
             // in order to leave final position unaltered
             i->set_offset(i->get_offset() + i->transform_vector(-shift, true));
+#endif // ENABLE_MIRROR
         }
         this->invalidate_bounding_box();
     }

src/libslic3r/Technologies.hpp

@@ -11,7 +11,7 @@
 // New selections
 #define ENABLE_EXTENDED_SELECTION (1 && ENABLE_1_42_0)
 // Add mirror components along the three axes in ModelInstance and GLVolume
-#define ENABLE_MIRROR (0 && ENABLE_1_42_0)
+#define ENABLE_MIRROR (1 && ENABLE_1_42_0)
 
 #endif // _technologies_h_