From 67572fad3f957bd5e40f3575e5e7f8fa3aebc66a Mon Sep 17 00:00:00 2001
From: enricoturri1966 <enricoturri@seznam.cz>
Date: Tue, 4 May 2021 14:48:30 +0200
Subject: [PATCH] Tech ENABLE_ALLOW_NEGATIVE_Z-> Keep sinking objects and
 instances as sinking after copy/paste or add instance commands

---
 src/slic3r/GUI/Plater.cpp | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index cce2dd319..32ecef438 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -5838,9 +5838,17 @@ void Plater::changed_objects(const std::vector<size_t>& object_idxs)
         return;
 
     for (size_t obj_idx : object_idxs) {
+#if ENABLE_ALLOW_NEGATIVE_Z
+        if (obj_idx < p->model.objects.size()) {
+            if (p->model.objects[obj_idx]->bounding_box().min.z() >= 0.0)
+                // re - align to Z = 0
+                p->model.objects[obj_idx]->ensure_on_bed();
+        }
+#else
         if (obj_idx < p->model.objects.size())
             // recenter and re - align to Z = 0
             p->model.objects[obj_idx]->ensure_on_bed();
+#endif // ENABLE_ALLOW_NEGATIVE_Z
     }
     if (this->p->printer_technology == ptSLA) {
         // Update the SLAPrint from the current Model, so that the reload_scene()