1 files changed, 21 insertions, 10 deletions

diff --git a/src/libslic3r/Layer.cpp b/src/libslic3r/Layer.cpp
index 29b20d2e1..975274445 100644
--- a/src/libslic3r/Layer.cpp
+++ b/src/libslic3r/Layer.cpp
@@ -64,19 +64,30 @@ void Layer::make_slices()
         this->lslices.emplace_back(std::move(slices[i]));
 }
 
-// Merge typed slices into untyped slices. This method is used to revert the effects of detect_surfaces_type() called for posPrepareInfill.
-void Layer::merge_slices()
+static inline bool layer_needs_raw_backup(const Layer *layer)
 {
-    if (m_regions.size() == 1 && (this->id() > 0 || this->object()->config().elefant_foot_compensation.value == 0)) {
-        // Optimization, also more robust. Don't merge classified pieces of layerm->slices,
-        // but use the non-split islands of a layer. For a single region print, these shall be equal.
-        // Don't use this optimization on 1st layer with Elephant foot compensation applied, as this->lslices are uncompensated,
-        // while regions are compensated.
-        m_regions.front()->slices.set(this->lslices, stInternal);
+    return ! (layer->regions().size() == 1 && (layer->id() > 0 || layer->object()->config().elefant_foot_compensation.value == 0));
+}
+
+void Layer::backup_untyped_slices()
+{
+    if (layer_needs_raw_backup(this)) {
+        for (LayerRegion *layerm : m_regions)
+            layerm->raw_slices = to_expolygons(layerm->slices.surfaces);
     } else {
+        assert(m_regions.size() == 1);
+        m_regions.front()->raw_slices.clear();
+    }
+}
+
+void Layer::restore_untyped_slices()
+{
+    if (layer_needs_raw_backup(this)) {
         for (LayerRegion *layerm : m_regions)
-            // without safety offset, artifacts are generated (upstream Slic3r GH #2494)
-            layerm->slices.set(union_ex(to_polygons(std::move(layerm->slices.surfaces)), true), stInternal);
+            layerm->slices.set(layerm->raw_slices, stInternal);
+    } else {
+        assert(m_regions.size() == 1);
+        m_regions.front()->slices.set(this->lslices, stInternal);
     }
 }