Fixed transformation of the hollowed mesh to be used at frontend

Common gizmos data update is called from GLGizmoManager

src/slic3r/GUI/Gizmos/GLGizmoBase.cpp

@@ -326,18 +326,24 @@ bool CommonGizmosData::update_from_backend(GLCanvas3D& canvas)
         }
     }
 
-    if (m_print_object_idx < 0)
-        return old_po_idx != m_print_object_idx;
-
     m_mesh = nullptr;
     // Load either the model_object mesh, or one provided by the backend
     // This mesh does not account for the possible Z up SLA offset.
-    const SLAPrintObject* po = canvas.sla_print()->objects()[m_print_object_idx];
+    // The backend mesh needs to be transformed and because a pointer to it is
+    // saved, a copy is stored as a member (FIXME)
+    if (m_print_object_idx >=0) {
+        const SLAPrintObject* po = canvas.sla_print()->objects()[m_print_object_idx];
+        if (po->is_step_done(slaposHollowing)) {
+            m_backend_mesh_transformed = po->get_mesh_to_print();
+            m_backend_mesh_transformed.transform(canvas.sla_print()->sla_trafo(*m_model_object).inverse());
+            m_mesh = &m_backend_mesh_transformed;
+        }
+    }
 
-    if (po->is_step_done(slaposHollowing))
-        m_mesh = &po->get_mesh_to_print();
-    else
+    if (! m_mesh) {
         m_mesh = &m_model_object->volumes.front()->mesh();
+        m_backend_mesh_transformed.clear();
+    }
 
     m_model_object_id = m_model_object->id();
 
@@ -348,7 +354,8 @@ bool CommonGizmosData::update_from_backend(GLCanvas3D& canvas)
         m_old_mesh = m_mesh;
         return true;
     }
-    return false;
+
+    return m_print_object_idx < 0 ? old_po_idx >=0 : false;
 }
 
 

src/slic3r/GUI/Gizmos/GLGizmoBase.hpp

@@ -215,6 +215,7 @@ public:
 
 private:
     const TriangleMesh* m_old_mesh;
+    TriangleMesh m_backend_mesh_transformed;
 };
 
 } // namespace GUI

src/slic3r/GUI/Gizmos/GLGizmoHollow.cpp

@@ -76,8 +76,10 @@ void GLGizmoHollow::set_sla_support_data(ModelObject* model_object, const Select
 
     if (model_object
      && selection.is_from_single_instance()
-     && (m_c->update_from_backend(m_parent) || something_changed))
+     && (something_changed))
     {
+        m_c->update_from_backend(m_parent);
+
         // Cache the bb - it's needed for dealing with the clipping plane quite often
         // It could be done inside update_mesh but one has to account for scaling of the instance.
         m_c->m_active_instance_bb_radius = m_c->m_model_object->instance_bounding_box(m_c->m_active_instance).radius();
@@ -580,7 +582,7 @@ void GLGizmoHollow::update_hollowed_mesh(std::unique_ptr<TriangleMesh> &&mesh)
 {
     // Called from Plater when the UI job finishes
     /*m_c->m_cavity_mesh = std::move(mesh);
-    
+
     if(m_c->m_cavity_mesh) {
         // First subtract the holes:
         if (! m_c->m_model_object->sla_drain_holes.empty()) {

src/slic3r/GUI/Gizmos/GLGizmoSlaSupports.cpp

@@ -1246,6 +1246,9 @@ void GLGizmoSlaSupports::reload_cache()
 
 bool GLGizmoSlaSupports::has_backend_supports() const
 {
+    if (! m_c->m_model_object)
+        return false;
+
     // find SlaPrintObject with this ID
     for (const SLAPrintObject* po : m_parent.sla_print()->objects()) {
         if (po->model_object()->id() == m_c->m_model_object->id())

src/slic3r/GUI/Gizmos/GLGizmosManager.cpp

@@ -348,6 +348,9 @@ void GLGizmosManager::set_sla_support_data(ModelObject* model_object)
     if (!m_enabled || m_gizmos.empty())
         return;
 
+    // Update common data for hollowing and sla support gizmos.
+    m_common_gizmos_data->update_from_backend(m_parent);
+
     dynamic_cast<GLGizmoSlaSupports*>(m_gizmos[SlaSupports].get())->set_sla_support_data(model_object, m_parent.get_selection());
     dynamic_cast<GLGizmoHollow*>(m_gizmos[Hollow].get())->set_sla_support_data(model_object, m_parent.get_selection());
 }