diff --git a/src/libslic3r/Model.cpp b/src/libslic3r/Model.cpp
index 3aa04f3b2..6b9151ff8 100644
--- a/src/libslic3r/Model.cpp
+++ b/src/libslic3r/Model.cpp
@@ -1232,6 +1232,19 @@ void ModelVolume::set_material(t_model_material_id material_id, const ModelMater
         this->object->get_model()->add_material(material_id, material);
 }
 
+// Extract the current extruder ID based on this ModelVolume's config and the parent ModelObject's config.
+int ModelVolume::extruder_id() const
+{
+    int extruder_id = -1;
+    if (this->is_model_part()) {
+        const ConfigOption *opt = this->config.option("extruder");
+        if (opt == nullptr)
+            opt = this->object->config.option("extruder");
+        extruder_id = (opt == nullptr) ? 0 : opt->getInt();
+    }
+    return extruder_id;
+}
+
 #if ENABLE_MODELVOLUME_TRANSFORM
 void ModelVolume::center_geometry()
 {
@@ -1525,6 +1538,71 @@ Transform3d ModelInstance::get_matrix(bool dont_translate, bool dont_rotate, boo
 }
 #endif // !ENABLE_MODELVOLUME_TRANSFORM
 
+// Test whether the two models contain the same number of ModelObjects with the same set of IDs
+// ordered in the same order. In that case it is not necessary to kill the background processing.
+bool model_object_list_equal(const Model &model_old, const Model &model_new)
+{
+    if (model_old.objects.size() != model_new.objects.size())
+        return false;
+    for (size_t i = 0; i < model_old.objects.size(); ++ i)
+        if (model_old.objects[i]->id() != model_new.objects[i]->id())
+            return false;
+    return true;
+}
+
+// Test whether the new model is just an extension of the old model (new objects were added
+// to the end of the original list. In that case it is not necessary to kill the background processing.
+bool model_object_list_extended(const Model &model_old, const Model &model_new)
+{
+    if (model_old.objects.size() >= model_new.objects.size())
+        return false;
+    for (size_t i = 0; i < model_old.objects.size(); ++ i)
+        if (model_old.objects[i]->id() != model_new.objects[i]->id())
+            return false;
+    return true;
+}
+
+bool model_volume_list_changed(const ModelObject &model_object_old, const ModelObject &model_object_new, const ModelVolume::Type type)
+{
+    bool modifiers_differ = false;
+    size_t i_old, i_new;
+    for (i_old = 0, i_new = 0; i_old < model_object_old.volumes.size() && i_new < model_object_new.volumes.size();) {
+        const ModelVolume &mv_old = *model_object_old.volumes[i_old];
+        const ModelVolume &mv_new = *model_object_new.volumes[i_new];
+        if (mv_old.type() != type) {
+            ++ i_old;
+            continue;
+        }
+        if (mv_new.type() != type) {
+            ++ i_new;
+            continue;
+        }
+        if (mv_old.id() != mv_new.id())
+            return true;
+        //FIXME test for the content of the mesh!
+
+#if ENABLE_MODELVOLUME_TRANSFORM
+        if (!mv_old.get_matrix().isApprox(mv_new.get_matrix()))
+            return true;
+#endif // ENABLE_MODELVOLUME_TRANSFORM
+        ++i_old;
+        ++ i_new;
+    }
+    for (; i_old < model_object_old.volumes.size(); ++ i_old) {
+        const ModelVolume &mv_old = *model_object_old.volumes[i_old];
+        if (mv_old.type() == type)
+            // ModelVolume was deleted.
+            return true;
+    }
+    for (; i_new < model_object_new.volumes.size(); ++ i_new) {
+        const ModelVolume &mv_new = *model_object_new.volumes[i_new];
+        if (mv_new.type() == type)
+            // ModelVolume was added.
+            return true;
+    }
+    return false;
+}
+
 #ifdef _DEBUG
 // Verify whether the IDs of Model / ModelObject / ModelVolume / ModelInstance / ModelMaterial are valid and unique.
 void check_model_ids_validity(const Model &model)
diff --git a/src/libslic3r/Model.hpp b/src/libslic3r/Model.hpp
index bf6656cfd..c288010d0 100644
--- a/src/libslic3r/Model.hpp
+++ b/src/libslic3r/Model.hpp
@@ -23,6 +23,7 @@ class ModelMaterial;
 class ModelObject;
 class ModelVolume;
 class Print;
+class SLAPrint;
 
 typedef std::string t_model_material_id;
 typedef std::string t_model_material_attribute;
@@ -252,6 +253,7 @@ public:
 
 protected:
     friend class Print;
+    friend class SLAPrint;
     // Called by Print::apply() to set the model pointer after making a copy.
     void        set_model(Model *model) { m_model = model; }
 
@@ -310,6 +312,10 @@ public:
     void                set_material_id(t_model_material_id material_id);
     ModelMaterial*      material() const;
     void                set_material(t_model_material_id material_id, const ModelMaterial &material);
+    // Extract the current extruder ID based on this ModelVolume's config and the parent ModelObject's config.
+    // Extruder ID is only valid for FFF. Returns -1 for SLA or if the extruder ID is not applicable (support volumes).
+    int                 extruder_id() const;
+
     // Split this volume, append the result to the object owning this volume.
     // Return the number of volumes created from this one.
     // This is useful to assign different materials to different volumes of an object.
@@ -368,6 +374,7 @@ public:
 
 protected:
 	friend class Print;
+    friend class SLAPrint;
 	friend class ModelObject;
 
 	explicit ModelVolume(const ModelVolume &rhs) = default;
@@ -535,6 +542,7 @@ public:
 
 protected:
     friend class Print;
+    friend class SLAPrint;
     friend class ModelObject;
 
     explicit ModelInstance(const ModelInstance &rhs) = default;
@@ -652,6 +660,18 @@ private:
 #undef MODELBASE_DERIVED_COPY_MOVE_CLONE
 #undef MODELBASE_DERIVED_PRIVATE_COPY_MOVE
 
+// Test whether the two models contain the same number of ModelObjects with the same set of IDs
+// ordered in the same order. In that case it is not necessary to kill the background processing.
+extern bool model_object_list_equal(const Model &model_old, const Model &model_new);
+
+// Test whether the new model is just an extension of the old model (new objects were added
+// to the end of the original list. In that case it is not necessary to kill the background processing.
+extern bool model_object_list_extended(const Model &model_old, const Model &model_new);
+
+// Test whether the new ModelObject contains a different set of volumes (or sorted in a different order)
+// than the old ModelObject.
+extern bool model_volume_list_changed(const ModelObject &model_object_old, const ModelObject &model_object_new, const ModelVolume::Type type);
+
 #ifdef _DEBUG
 // Verify whether the IDs of Model / ModelObject / ModelVolume / ModelInstance / ModelMaterial are valid and unique.
 void check_model_ids_validity(const Model &model);
diff --git a/src/libslic3r/Print.cpp b/src/libslic3r/Print.cpp
index 4e1685e45..b14132ad6 100644
--- a/src/libslic3r/Print.cpp
+++ b/src/libslic3r/Print.cpp
@@ -550,71 +550,6 @@ exit_for_rearrange_regions:
     return invalidated;
 }
 
-// Test whether the two models contain the same number of ModelObjects with the same set of IDs
-// ordered in the same order. In that case it is not necessary to kill the background processing.
-static inline bool model_object_list_equal(const Model &model_old, const Model &model_new)
-{
-    if (model_old.objects.size() != model_new.objects.size())
-        return false;
-    for (size_t i = 0; i < model_old.objects.size(); ++ i)
-        if (model_old.objects[i]->id() != model_new.objects[i]->id())
-            return false;
-    return true;
-}
-
-// Test whether the new model is just an extension of the old model (new objects were added
-// to the end of the original list. In that case it is not necessary to kill the background processing.
-static inline bool model_object_list_extended(const Model &model_old, const Model &model_new)
-{
-    if (model_old.objects.size() >= model_new.objects.size())
-        return false;
-    for (size_t i = 0; i < model_old.objects.size(); ++ i)
-        if (model_old.objects[i]->id() != model_new.objects[i]->id())
-            return false;
-    return true;
-}
-
-static inline bool model_volume_list_changed(const ModelObject &model_object_old, const ModelObject &model_object_new, const ModelVolume::Type type)
-{
-    bool modifiers_differ = false;
-    size_t i_old, i_new;
-    for (i_old = 0, i_new = 0; i_old < model_object_old.volumes.size() && i_new < model_object_new.volumes.size();) {
-        const ModelVolume &mv_old = *model_object_old.volumes[i_old];
-		const ModelVolume &mv_new = *model_object_new.volumes[i_new];
-        if (mv_old.type() != type) {
-            ++ i_old;
-            continue;
-        }
-        if (mv_new.type() != type) {
-            ++ i_new;
-            continue;
-        }
-        if (mv_old.id() != mv_new.id())
-            return true;
-        //FIXME test for the content of the mesh!
-
-#if ENABLE_MODELVOLUME_TRANSFORM
-        if (!mv_old.get_matrix().isApprox(mv_new.get_matrix()))
-            return true;
-#endif // ENABLE_MODELVOLUME_TRANSFORM
-        ++i_old;
-        ++ i_new;
-    }
-    for (; i_old < model_object_old.volumes.size(); ++ i_old) {
-        const ModelVolume &mv_old = *model_object_old.volumes[i_old];
-        if (mv_old.type() == type)
-            // ModelVolume was deleted.
-            return true;
-    }
-    for (; i_new < model_object_new.volumes.size(); ++ i_new) {
-        const ModelVolume &mv_new = *model_object_new.volumes[i_new];
-        if (mv_new.type() == type)
-            // ModelVolume was added.
-            return true;
-    }
-    return false;
-}
-
 // Add or remove support modifier ModelVolumes from model_object_dst to match the ModelVolumes of model_object_new
 // in the exact order and with the same IDs.
 // It is expected, that the model_object_dst already contains the non-support volumes of model_object_new in the correct order.
diff --git a/src/libslic3r/Print.hpp b/src/libslic3r/Print.hpp
index 0f6c0afbd..b5c693ee4 100644
--- a/src/libslic3r/Print.hpp
+++ b/src/libslic3r/Print.hpp
@@ -131,9 +131,6 @@ public:
     SupportLayerPtrs::const_iterator insert_support_layer(SupportLayerPtrs::const_iterator pos, int id, coordf_t height, coordf_t print_z, coordf_t slice_z);
     void delete_support_layer(int idx);
     
-    // methods for handling state
-    bool invalidate_state_by_config_options(const std::vector<t_config_option_key> &opt_keys);
-
     // To be used over the layer_height_profile of both the PrintObject and ModelObject
     // to initialize the height profile with the height ranges.
     bool update_layer_height_profile(std::vector<coordf_t> &layer_height_profile) const;
@@ -174,6 +171,8 @@ protected:
     bool                    invalidate_step(PrintObjectStep step);
     // Invalidates all PrintObject and Print steps.
     bool                    invalidate_all_steps();
+    // Invalidate steps based on a set of parameters changed.
+    bool                    invalidate_state_by_config_options(const std::vector<t_config_option_key> &opt_keys);
 
 private:
     void make_perimeters();
diff --git a/src/libslic3r/PrintConfig.cpp b/src/libslic3r/PrintConfig.cpp
index 055d7e46a..739b7ee22 100644
--- a/src/libslic3r/PrintConfig.cpp
+++ b/src/libslic3r/PrintConfig.cpp
@@ -2447,6 +2447,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_head_front_radius", coFloat);
     def->label = L("Support head front radius");
+    def->category = L("Supports");
     def->tooltip = L("Radius of the pointing side of the head");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2455,6 +2456,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_head_penetration", coFloat);
     def->label = L("Support head penetration");
+    def->category = L("Supports");
     def->tooltip = L("How much the pinhead has to penetrate the model surface");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2463,6 +2465,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_head_back_radius", coFloat);
     def->label = L("Support head back radius");
+    def->category = L("Supports");
     def->tooltip = L("Radius of the back side of the 3d arrow");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2471,6 +2474,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_head_width", coFloat);
     def->label = L("Support head width");
+    def->category = L("Supports");
     def->tooltip = L("Width from the back sphere center to the front sphere center");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2479,6 +2483,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_pillar_radius", coFloat);
     def->label = L("Support pillar radius");
+    def->category = L("Supports");
     def->tooltip = L("Radius in mm of the support pillars");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2487,6 +2492,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_base_radius", coFloat);
     def->label = L("Support base radius");
+    def->category = L("Supports");
     def->tooltip = L("Radius in mm of the pillar base");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2495,6 +2501,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_base_height", coFloat);
     def->label = L("Support base height");
+    def->category = L("Supports");
     def->tooltip = L("The height of the pillar base cone");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2503,6 +2510,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_critical_angle", coFloat);
     def->label = L("Critical angle");
+    def->category = L("Supports");
     def->tooltip = L("The default angle for connecting support sticks and junctions.");
     def->sidetext = L("°");
     def->cli = "";
@@ -2511,6 +2519,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_max_bridge_length", coFloat);
     def->label = L("Max bridge length");
+    def->category = L("Supports");
     def->tooltip = L("The max length of a bridge");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2519,6 +2528,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("support_object_elevation", coFloat);
     def->label = L("Object elevation");
+    def->category = L("Supports");
     def->tooltip = L("How much the supports should lift up the supported object.");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2527,6 +2537,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("pad_enable", coBool);
     def->label = L("Use pad");
+    def->category = L("Pad");
     def->tooltip = L("Add a pad underneath the supported model");
     def->sidetext = L("");
     def->cli = "";
@@ -2534,6 +2545,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("pad_wall_thickness", coFloat);
     def->label = L("Pad wall thickness");
+    def->category = L("Pad");
     def->tooltip = L("");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2542,6 +2554,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("pad_wall_height", coFloat);
     def->label = L("Pad wall height");
+    def->category = L("Pad");
     def->tooltip = L("");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2550,6 +2563,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("pad_max_merge_distance", coFloat);
     def->label = L("Max merge distance");
+    def->category = L("Pad");
     def->tooltip = L("");
     def->sidetext = L("mm");
     def->cli = "";
@@ -2558,6 +2572,7 @@ void PrintConfigDef::init_sla_params()
 
     def = this->add("pad_edge_radius", coFloat);
     def->label = L("Pad edge radius");
+    def->category = L("Pad");
     def->tooltip = L("");
     def->sidetext = L("mm");
     def->cli = "";
diff --git a/src/libslic3r/PrintConfig.hpp b/src/libslic3r/PrintConfig.hpp
index f1d1c9784..a3c79f4a4 100644
--- a/src/libslic3r/PrintConfig.hpp
+++ b/src/libslic3r/PrintConfig.hpp
@@ -902,7 +902,7 @@ class SLAPrintObjectConfig : public StaticPrintConfig
 {
     STATIC_PRINT_CONFIG_CACHE(SLAPrintObjectConfig)
 public:
-    ConfigOptionFloat                       layer_height;
+    ConfigOptionFloat layer_height;
 
     // Radius in mm of the pointing side of the head.
     ConfigOptionFloat support_head_front_radius /*= 0.2*/;
diff --git a/src/libslic3r/SLAPrint.cpp b/src/libslic3r/SLAPrint.cpp
index 085e490e7..9f1ba4cc0 100644
--- a/src/libslic3r/SLAPrint.cpp
+++ b/src/libslic3r/SLAPrint.cpp
@@ -3,6 +3,8 @@
 #include "SLA/SLABasePool.hpp"
 #include "MTUtils.hpp"
 
+#include <unordered_set>
+
 #include <tbb/parallel_for.h>
 #include <boost/log/trivial.hpp>
 
@@ -75,53 +77,296 @@ void SLAPrint::clear()
 	m_objects.clear();
 }
 
+// Transformation without rotation around Z and without a shift by X and Y.
+static Transform3d sla_trafo(const ModelObject &model_object)
+{
+    ModelInstance &model_instance = *model_object.instances.front();
+    Vec3d          offset         = model_instance.get_offset();
+    Vec3d          rotation       = model_instance.get_rotation();
+    offset(0) = 0.;
+    offset(1) = 0.;
+    rotation(2) = 0.;
+    return Geometry::assemble_transform(offset, rotation, model_instance.get_scaling_factor(), model_instance.get_mirror());
+}
+
+// List of instances, where the ModelInstance transformation is a composite of sla_trafo and the transformation defined by SLAPrintObject::Instance.
+static std::vector<SLAPrintObject::Instance> sla_instances(const ModelObject &model_object)
+{
+    std::vector<SLAPrintObject::Instance> instances;
+    for (ModelInstance *model_instance : model_object.instances)
+        if (model_instance->is_printable()) {
+            instances.emplace_back(SLAPrintObject::Instance(
+                model_instance->id(), 
+                Point::new_scale(model_instance->get_offset(X), model_instance->get_offset(Y)),
+                float(model_instance->get_rotation(Z))));
+        }
+    return instances;
+}
+
 SLAPrint::ApplyStatus SLAPrint::apply(const Model &model,
                                       const DynamicPrintConfig &config_in)
 {
-//	if (m_objects.empty())
-//		return APPLY_STATUS_UNCHANGED;
+#ifdef _DEBUG
+    check_model_ids_validity(model);
+#endif /* _DEBUG */
+
+    // Make a copy of the config, normalize it.
+    DynamicPrintConfig config(config_in);
+    config.normalize();
+    // Collect changes to print config.
+    t_config_option_keys printer_diff  = m_printer_config.diff(config);
+    t_config_option_keys material_diff = m_material_config.diff(config);
+    t_config_option_keys object_diff   = m_default_object_config.diff(config);
+
+    // Do not use the ApplyStatus as we will use the max function when updating apply_status. 
+    unsigned int apply_status = APPLY_STATUS_UNCHANGED;
+    auto update_apply_status = [&apply_status](bool invalidated)
+        { apply_status = std::max<unsigned int>(apply_status, invalidated ? APPLY_STATUS_INVALIDATED : APPLY_STATUS_CHANGED); };
+    if (! (printer_diff.empty() && material_diff.empty() && object_diff.empty()))
+        update_apply_status(false);
 
     // Grab the lock for the Print / PrintObject milestones.
 	tbb::mutex::scoped_lock lock(this->state_mutex());
-	if (m_objects.empty() && model.objects.empty() && m_model.objects.empty())
-        return APPLY_STATUS_UNCHANGED;
 
-    // Temporary: just to have to correct layer height for the rasterization
-    DynamicPrintConfig config(config_in);
-    config.normalize();
-    m_material_config.initial_layer_height.set(
-                config.opt<ConfigOptionFloat>("initial_layer_height"));
+    // The following call may stop the background processing.
+    update_apply_status(this->invalidate_state_by_config_options(printer_diff));
+    update_apply_status(this->invalidate_state_by_config_options(material_diff));
 
-	// Temporary quick fix, just invalidate everything.
-    {
-        for (SLAPrintObject *print_object : m_objects) {
-			print_object->invalidate_all_steps();
-            delete print_object;
-		}
-		m_objects.clear();
-		this->invalidate_all_steps();
+    // It is also safe to change m_config now after this->invalidate_state_by_config_options() call.
+	m_printer_config.apply_only(config, printer_diff, true);
+    // Handle changes to material config.
+    m_material_config.apply_only(config, material_diff, true);
+    // Handle changes to object config defaults
+    m_default_object_config.apply_only(config, object_diff, true);
 
-        // Copy the model by value (deep copy),
-        // keep the Model / ModelObject / ModelInstance / ModelVolume IDs.
+    struct ModelObjectStatus {
+        enum Status {
+            Unknown,
+            Old,
+            New,
+            Moved,
+            Deleted,
+        };
+        ModelObjectStatus(ModelID id, Status status = Unknown) : id(id), status(status) {}
+        ModelID                 id;
+        Status                  status;
+        // Search by id.
+        bool operator<(const ModelObjectStatus &rhs) const { return id < rhs.id; }
+    };
+    std::set<ModelObjectStatus> model_object_status;
+
+    // 1) Synchronize model objects.
+    if (model.id() != m_model.id()) {
+        // Kill everything, initialize from scratch.
+        // Stop background processing.
+        this->call_cancell_callback();
+        update_apply_status(this->invalidate_all_steps());
+        for (SLAPrintObject *object : m_objects) {
+            model_object_status.emplace(object->model_object()->id(), ModelObjectStatus::Deleted);
+            delete object;
+        }
+        m_objects.clear();
         m_model.assign_copy(model);
-        // Generate new SLAPrintObjects.
-        for (ModelObject *model_object : m_model.objects) {
-            auto po = new SLAPrintObject(this, model_object);
-
-            // po->m_config.layer_height.set(lh);
-            po->m_config.apply(config, true);
-
-            m_objects.emplace_back(po);
-            for (ModelInstance *oinst : model_object->instances) {
-                Point tr = Point::new_scale(oinst->get_offset()(X),
-                                            oinst->get_offset()(Y));
-                auto rotZ = float(oinst->get_rotation()(Z));
-				po->m_instances.emplace_back(oinst->id(), tr, rotZ);
+        for (const ModelObject *model_object : m_model.objects)
+            model_object_status.emplace(model_object->id(), ModelObjectStatus::New);
+    } else {
+        if (model_object_list_equal(m_model, model)) {
+            // The object list did not change.
+            for (const ModelObject *model_object : m_model.objects)
+                model_object_status.emplace(model_object->id(), ModelObjectStatus::Old);
+        } else if (model_object_list_extended(m_model, model)) {
+            // Add new objects. Their volumes and configs will be synchronized later.
+            update_apply_status(this->invalidate_step(slapsRasterize));
+            for (const ModelObject *model_object : m_model.objects)
+                model_object_status.emplace(model_object->id(), ModelObjectStatus::Old);
+            for (size_t i = m_model.objects.size(); i < model.objects.size(); ++ i) {
+                model_object_status.emplace(model.objects[i]->id(), ModelObjectStatus::New);
+                m_model.objects.emplace_back(ModelObject::new_copy(*model.objects[i]));
+                m_model.objects.back()->set_model(&m_model);
+            }
+        } else {
+            // Reorder the objects, add new objects.
+            // First stop background processing before shuffling or deleting the PrintObjects in the object list.
+            this->call_cancell_callback();
+            update_apply_status(this->invalidate_step(slapsRasterize));
+            // Second create a new list of objects.
+            std::vector<ModelObject*> model_objects_old(std::move(m_model.objects));
+            m_model.objects.clear();
+            m_model.objects.reserve(model.objects.size());
+            auto by_id_lower = [](const ModelObject *lhs, const ModelObject *rhs){ return lhs->id() < rhs->id(); };
+            std::sort(model_objects_old.begin(), model_objects_old.end(), by_id_lower);
+            for (const ModelObject *mobj : model.objects) {
+                auto it = std::lower_bound(model_objects_old.begin(), model_objects_old.end(), mobj, by_id_lower);
+                if (it == model_objects_old.end() || (*it)->id() != mobj->id()) {
+                    // New ModelObject added.
+                    m_model.objects.emplace_back(ModelObject::new_copy(*mobj));
+                    m_model.objects.back()->set_model(&m_model);
+                    model_object_status.emplace(mobj->id(), ModelObjectStatus::New);
+                } else {
+                    // Existing ModelObject re-added (possibly moved in the list).
+                    m_model.objects.emplace_back(*it);
+                    model_object_status.emplace(mobj->id(), ModelObjectStatus::Moved);
+                }
+            }
+            bool deleted_any = false;
+            for (ModelObject *&model_object : model_objects_old) {
+                if (model_object_status.find(ModelObjectStatus(model_object->id())) == model_object_status.end()) {
+                    model_object_status.emplace(model_object->id(), ModelObjectStatus::Deleted);
+                    deleted_any = true;
+                } else
+                    // Do not delete this ModelObject instance.
+                    model_object = nullptr;
+            }
+            if (deleted_any) {
+                // Delete PrintObjects of the deleted ModelObjects.
+                std::vector<SLAPrintObject*> print_objects_old = std::move(m_objects);
+                m_objects.clear();
+                m_objects.reserve(print_objects_old.size());
+                for (SLAPrintObject *print_object : print_objects_old) {
+                    auto it_status = model_object_status.find(ModelObjectStatus(print_object->model_object()->id()));
+                    assert(it_status != model_object_status.end());
+                    if (it_status->status == ModelObjectStatus::Deleted) {
+                        update_apply_status(print_object->invalidate_all_steps());
+                        delete print_object;
+                    } else
+                        m_objects.emplace_back(print_object);
+                }
+                for (ModelObject *model_object : model_objects_old)
+                    delete model_object;
             }
         }
     }
 
-	return APPLY_STATUS_INVALIDATED;
+    // 2) Map print objects including their transformation matrices.
+    struct PrintObjectStatus {
+        enum Status {
+            Unknown,
+            Deleted,
+            Reused,
+            New
+        };
+        PrintObjectStatus(SLAPrintObject *print_object, Status status = Unknown) : 
+            id(print_object->model_object()->id()),
+            print_object(print_object),
+            trafo(print_object->trafo()),
+            status(status) {}
+        PrintObjectStatus(ModelID id) : id(id), print_object(nullptr), trafo(Transform3d::Identity()), status(Unknown) {}
+        // ID of the ModelObject & PrintObject
+        ModelID          id;
+        // Pointer to the old PrintObject
+        SLAPrintObject  *print_object;
+        // Trafo generated with model_object->world_matrix(true) 
+        Transform3d      trafo;
+        Status           status;
+        // Search by id.
+        bool operator<(const PrintObjectStatus &rhs) const { return id < rhs.id; }
+    };
+    std::multiset<PrintObjectStatus> print_object_status;
+    for (SLAPrintObject *print_object : m_objects)
+        print_object_status.emplace(PrintObjectStatus(print_object));
+
+    // 3) Synchronize ModelObjects & PrintObjects.
+    std::vector<SLAPrintObject*> print_objects_new;
+    print_objects_new.reserve(std::max(m_objects.size(), m_model.objects.size()));
+    bool new_objects = false;
+    for (size_t idx_model_object = 0; idx_model_object < model.objects.size(); ++ idx_model_object) {
+        ModelObject &model_object = *m_model.objects[idx_model_object];
+        auto it_status = model_object_status.find(ModelObjectStatus(model_object.id()));
+        assert(it_status != model_object_status.end());
+        assert(it_status->status != ModelObjectStatus::Deleted);
+        if (it_status->status == ModelObjectStatus::New)
+            // PrintObject instances will be added in the next loop.
+            continue;
+        // Update the ModelObject instance, possibly invalidate the linked PrintObjects.
+        assert(it_status->status == ModelObjectStatus::Old || it_status->status == ModelObjectStatus::Moved);
+        const ModelObject &model_object_new       = *model.objects[idx_model_object];
+        auto               it_print_object_status = print_object_status.lower_bound(PrintObjectStatus(model_object.id()));
+		if (it_print_object_status != print_object_status.end() && it_print_object_status->id != model_object.id())
+            it_print_object_status = print_object_status.end();
+        // Check whether a model part volume was added or removed, their transformations or order changed.
+        bool model_parts_differ = model_volume_list_changed(model_object, model_object_new, ModelVolume::MODEL_PART);
+        bool sla_trafo_differs  = model_object.instances.empty() != model_object_new.instances.empty() || 
+            (! model_object.instances.empty() && ! sla_trafo(model_object).isApprox(sla_trafo(model_object_new)));
+        if (model_parts_differ || sla_trafo_differs) {
+            // The very first step (the slicing step) is invalidated. One may freely remove all associated PrintObjects.
+			if (it_print_object_status != print_object_status.end()) {
+				update_apply_status(it_print_object_status->print_object->invalidate_all_steps());
+				const_cast<PrintObjectStatus&>(*it_print_object_status).status = PrintObjectStatus::Deleted;
+            }
+            // Copy content of the ModelObject including its ID, do not change the parent.
+            model_object.assign_copy(model_object_new);
+        } else {
+            // Synchronize Object's config.
+            bool object_config_changed = model_object.config != model_object_new.config;
+            if (object_config_changed)
+                model_object.config = model_object_new.config;
+            if (! object_diff.empty() || object_config_changed) {
+                SLAPrintObjectConfig new_config = m_default_object_config;
+                normalize_and_apply_config(new_config, model_object.config);
+                if (it_print_object_status != print_object_status.end()) {
+					t_config_option_keys diff = it_print_object_status->print_object->config().diff(new_config);
+                    if (! diff.empty()) {
+                        update_apply_status(it_print_object_status->print_object->invalidate_state_by_config_options(diff));
+                        it_print_object_status->print_object->config_apply_only(new_config, diff, true);
+                    }
+                }
+            }
+            if (model_object.sla_support_points != model_object_new.sla_support_points) {
+                model_object.sla_support_points = model_object_new.sla_support_points;
+                if (it_print_object_status != print_object_status.end())
+                    update_apply_status(it_print_object_status->print_object->invalidate_step(slaposSupportPoints));
+            }
+            // Copy the ModelObject name, input_file and instances. The instances will compared against PrintObject instances in the next step.
+            model_object.name       = model_object_new.name;
+            model_object.input_file = model_object_new.input_file;
+            model_object.clear_instances();
+            model_object.instances.reserve(model_object_new.instances.size());
+            for (const ModelInstance *model_instance : model_object_new.instances) {
+                model_object.instances.emplace_back(new ModelInstance(*model_instance));
+                model_object.instances.back()->set_model_object(&model_object);
+            }
+        }
+
+        std::vector<SLAPrintObject::Instance> new_instances = sla_instances(model_object);
+        if (it_print_object_status != print_object_status.end() && it_print_object_status->status != PrintObjectStatus::Deleted) {
+            // The SLAPrintObject is already there.
+            if (new_instances != it_print_object_status->print_object->instances()) {
+                // Instances changed.
+                it_print_object_status->print_object->set_instances(new_instances);
+                update_apply_status(this->invalidate_step(slapsRasterize));
+            }
+            print_objects_new.emplace_back(it_print_object_status->print_object);
+            const_cast<PrintObjectStatus&>(*it_print_object_status).status = PrintObjectStatus::Reused;
+        } else {
+            auto print_object = new SLAPrintObject(this, &model_object);
+            print_object->set_trafo(sla_trafo(model_object));
+            print_object->set_instances(new_instances);
+            print_object->config_apply(config, true);
+            print_objects_new.emplace_back(print_object);
+            new_objects = true;
+        }
+    }
+
+    if (m_objects != print_objects_new) {
+        this->call_cancell_callback();
+        update_apply_status(this->invalidate_all_steps());
+        m_objects = print_objects_new;
+        // Delete the PrintObjects marked as Unknown or Deleted.
+        bool deleted_objects = false;
+        for (auto &pos : print_object_status)
+            if (pos.status == PrintObjectStatus::Unknown || pos.status == PrintObjectStatus::Deleted) {
+                // update_apply_status(pos.print_object->invalidate_all_steps());
+                delete pos.print_object;
+                deleted_objects = true;
+            }
+        update_apply_status(new_objects);
+    }
+
+#ifdef _DEBUG
+    check_model_ids_equal(m_model, model);
+#endif /* _DEBUG */
+
+    return static_cast<ApplyStatus>(apply_status);
 }
 
 void SLAPrint::process()
@@ -418,12 +663,12 @@ void SLAPrint::process()
 
             // Status indication
             auto st = ist + unsigned(sd*level_id*slot/levels.size());
-            slck.lock();
+            { std::lock_guard<SpinMutex> lck(slck);
             if( st > pst) {
                 set_status(st, PRINT_STEP_LABELS[slapsRasterize]);
                 pst = st;
             }
-            slck.unlock();
+            }
         };
 
         // last minute escape
@@ -534,6 +779,61 @@ void SLAPrint::process()
     set_status(100, L("Slicing done"));
 }
 
+bool SLAPrint::invalidate_state_by_config_options(const std::vector<t_config_option_key> &opt_keys)
+{
+    if (opt_keys.empty())
+        return false;
+
+    // Cache the plenty of parameters, which influence the final rasterization only,
+    // or they are only notes not influencing the rasterization step.
+    static std::unordered_set<std::string> steps_rasterize = {
+        "exposure_time",
+        "initial_exposure_time",
+        "material_correction_printing",
+        "material_correction_curing",
+        "display_width",
+        "display_height",
+        "display_pixels_x",
+        "display_pixels_y",
+        "printer_correction"
+    };
+
+    static std::unordered_set<std::string> steps_ignore = {
+        "bed_shape",
+        "max_print_height",
+        "printer_technology",
+    };
+
+    std::vector<SLAPrintStep> steps;
+    std::vector<SLAPrintObjectStep> osteps;
+    bool invalidated = false;
+
+    for (const t_config_option_key &opt_key : opt_keys) {
+        if (steps_rasterize.find(opt_key) != steps_rasterize.end()) {
+            // These options only affect the final rasterization, or they are just notes without influence on the output,
+            // so there is nothing to invalidate.
+            steps.emplace_back(slapsRasterize);
+        } else if (steps_ignore.find(opt_key) != steps_ignore.end()) {
+            // These steps have no influence on the output. Just ignore them.
+        } else if (opt_key == "initial_layer_height") {
+            steps.emplace_back(slapsRasterize);
+            osteps.emplace_back(slaposObjectSlice);
+        } else {
+            // All values should be covered.
+            assert(false);
+        }
+    }
+
+    sort_remove_duplicates(steps);
+    for (SLAPrintStep step : steps)
+        invalidated |= this->invalidate_step(step);
+    sort_remove_duplicates(osteps);
+    for (SLAPrintObjectStep ostep : osteps)
+        for (SLAPrintObject *object : m_objects)
+            invalidated |= object->invalidate_step(ostep);
+    return invalidated;
+}
+
 SLAPrintObject::SLAPrintObject(SLAPrint *print, ModelObject *model_object):
     Inherited(print, model_object),
     m_stepmask(slaposCount, true),
@@ -545,6 +845,75 @@ SLAPrintObject::SLAPrintObject(SLAPrint *print, ModelObject *model_object):
 
 SLAPrintObject::~SLAPrintObject() {}
 
+// Called by SLAPrint::apply_config().
+// This method only accepts SLAPrintObjectConfig option keys.
+bool SLAPrintObject::invalidate_state_by_config_options(const std::vector<t_config_option_key> &opt_keys)
+{
+    if (opt_keys.empty())
+        return false;
+
+    std::vector<SLAPrintObjectStep> steps;
+    bool invalidated = false;
+    for (const t_config_option_key &opt_key : opt_keys) {
+        if (   opt_key == "support_head_front_radius"
+            || opt_key == "support_head_penetration"
+            || opt_key == "support_head_back_radius"
+            || opt_key == "support_head_width"
+            || opt_key == "support_pillar_radius"
+            || opt_key == "support_base_radius"
+            || opt_key == "support_base_height"
+            || opt_key == "support_critical_angle"
+            || opt_key == "support_max_bridge_length"
+            || opt_key == "support_object_elevation") {
+            steps.emplace_back(slaposSupportTree);
+        } else if (
+               opt_key == "pad_enable"
+            || opt_key == "pad_wall_thickness"
+            || opt_key == "pad_wall_height"
+            || opt_key == "pad_max_merge_distance"
+            || opt_key == "pad_edge_radius") {
+            steps.emplace_back(slaposBasePool);
+        } else {
+            // All keys should be covered.
+            assert(false);
+        }
+    }
+
+    sort_remove_duplicates(steps);
+    for (SLAPrintObjectStep step : steps)
+        invalidated |= this->invalidate_step(step);
+    return invalidated;
+}
+
+bool SLAPrintObject::invalidate_step(SLAPrintObjectStep step)
+{
+    bool invalidated = Inherited::invalidate_step(step);
+    // propagate to dependent steps
+    if (step == slaposObjectSlice) {
+        invalidated |= this->invalidate_all_steps();
+    } else if (step == slaposSupportIslands) {
+        invalidated |= this->invalidate_steps({ slaposSupportPoints, slaposSupportTree, slaposBasePool, slaposSliceSupports });
+        invalidated |= m_print->invalidate_step(slapsRasterize);
+    } else if (step == slaposSupportPoints) {
+        invalidated |= this->invalidate_steps({ slaposSupportTree, slaposBasePool, slaposSliceSupports });
+        invalidated |= m_print->invalidate_step(slapsRasterize);
+    } else if (step == slaposSupportTree) {
+        invalidated |= this->invalidate_steps({ slaposBasePool, slaposSliceSupports });
+        invalidated |= m_print->invalidate_step(slapsRasterize);
+    } else if (step == slaposBasePool) {
+        invalidated |= this->invalidate_step(slaposSliceSupports);
+        invalidated |= m_print->invalidate_step(slapsRasterize);
+    } else if (step == slaposSliceSupports) {
+        invalidated |= m_print->invalidate_step(slapsRasterize);
+    }
+    return invalidated;
+}
+
+bool SLAPrintObject::invalidate_all_steps()
+{
+    return Inherited::invalidate_all_steps() | m_print->invalidate_all_steps();
+}
+
 double SLAPrintObject::get_elevation() const {
     double ret = m_config.support_object_elevation.getFloat();
 
@@ -565,6 +934,18 @@ double SLAPrintObject::get_elevation() const {
     return ret;
 }
 
+double SLAPrintObject::get_current_elevation() const
+{
+    bool has_supports = is_step_done(slaposSupportTree);
+    bool has_pad = is_step_done(slaposBasePool);
+    if(!has_supports && !has_pad) return 0;
+    else if(has_supports && !has_pad)
+        return m_config.support_object_elevation.getFloat();
+    else return get_elevation();
+
+    return 0;
+}
+
 namespace { // dummy empty static containers for return values in some methods
 const std::vector<ExPolygons> EMPTY_SLICES;
 const TriangleMesh EMPTY_MESH;
diff --git a/src/libslic3r/SLAPrint.hpp b/src/libslic3r/SLAPrint.hpp
index ae797e9fb..704508278 100644
--- a/src/libslic3r/SLAPrint.hpp
+++ b/src/libslic3r/SLAPrint.hpp
@@ -38,16 +38,18 @@ private: // Prevents erroneous use by other classes.
     using Inherited = _SLAPrintObjectBase;
 
 public:
-    const Transform3d&      trafo()        const    { return m_trafo; }
+    const SLAPrintObjectConfig& config() const { return m_config; }
+    const Transform3d&          trafo()  const { return m_trafo; }
 
     struct Instance {
     	Instance(ModelID instance_id, const Point &shift, float rotation) : instance_id(instance_id), shift(shift), rotation(rotation) {}
+		bool operator==(const Instance &rhs) const { return this->instance_id == rhs.instance_id && this->shift == rhs.shift && this->rotation == rhs.rotation; }
     	// ID of the corresponding ModelInstance.
 		ModelID instance_id;
 		// Slic3r::Point objects in scaled G-code coordinates
     	Point 	shift;
     	// Rotation along the Z axis, in radians.
-    	float 	rotation; 
+    	float 	rotation;
 	};
     const std::vector<Instance>& instances() const { return m_instances; }
 
@@ -72,6 +74,11 @@ public:
     // as the pad height also needs to be considered.
     double get_elevation() const;
 
+    // This method returns the needed elevation according to the processing
+    // status. If the supports are not ready, it is zero, if they are and the
+    // pad is not, then without the pad, otherwise the full value is returned.
+    double get_current_elevation() const;
+
     // Should be obvious
     const std::vector<ExPolygons>& get_support_slices() const;
     const std::vector<ExPolygons>& get_model_slices() const;
@@ -95,12 +102,14 @@ protected:
         m_transformed_rmesh.invalidate([this, &trafo](){ m_trafo = trafo; });
     }
 
-    bool                    set_instances(const std::vector<Instance> &instances);
+    void                    set_instances(const std::vector<Instance> &instances) { m_instances = instances; }
     // Invalidates the step, and its depending steps in SLAPrintObject and SLAPrint.
     bool                    invalidate_step(SLAPrintObjectStep step);
+    bool                    invalidate_all_steps();
+    // Invalidate steps based on a set of parameters changed.
+    bool                    invalidate_state_by_config_options(const std::vector<t_config_option_key> &opt_keys);
 
 private:
-
     // Object specific configuration, pulled from the configuration layer.
     SLAPrintObjectConfig                    m_config;
     // Translation in Z + Rotation by Y and Z + Scaling / Mirroring.
@@ -143,7 +152,7 @@ public:
 	PrinterTechnology	technology() const noexcept { return ptSLA; }
 
     void                clear() override;
-    bool                empty() const override { return false; }
+    bool                empty() const override { return m_objects.empty(); }
     ApplyStatus         apply(const Model &model, const DynamicPrintConfig &config) override;
     void                process() override;
 
@@ -156,8 +165,13 @@ private:
     using SLAPrinter = FilePrinter<FilePrinterFormat::SLA_PNGZIP>;
     using SLAPrinterPtr = std::unique_ptr<SLAPrinter>;
 
+    // Invalidate steps based on a set of parameters changed.
+    bool invalidate_state_by_config_options(const std::vector<t_config_option_key> &opt_keys);
+
     SLAPrinterConfig                m_printer_config;
     SLAMaterialConfig               m_material_config;
+    SLAPrintObjectConfig            m_default_object_config;
+
     PrintObjects                    m_objects;
     std::vector<bool>               m_stepmask;
     SLAPrinterPtr                   m_printer;
diff --git a/src/libslic3r/Technologies.hpp b/src/libslic3r/Technologies.hpp
index f7ab20088..17459dde5 100644
--- a/src/libslic3r/Technologies.hpp
+++ b/src/libslic3r/Technologies.hpp
@@ -31,6 +31,8 @@
 #define ENABLE_NEW_MENU_LAYOUT (1 && ENABLE_1_42_0)
 // All rotations made using the rotate gizmo are done with respect to the world reference system
 #define ENABLE_WORLD_ROTATIONS (1 && ENABLE_1_42_0)
+// Enables shortcut keys for gizmos
+#define ENABLE_GIZMOS_SHORTCUT (1 && ENABLE_1_42_0)
 
 #endif // _technologies_h_
 
diff --git a/src/slic3r/GUI/3DScene.cpp b/src/slic3r/GUI/3DScene.cpp
index 8635c2a57..193673260 100644
--- a/src/slic3r/GUI/3DScene.cpp
+++ b/src/slic3r/GUI/3DScene.cpp
@@ -201,6 +201,8 @@ const float GLVolume::HOVER_COLOR[4] = { 0.4f, 0.9f, 0.1f, 1.0f };
 const float GLVolume::OUTSIDE_COLOR[4] = { 0.0f, 0.38f, 0.8f, 1.0f };
 const float GLVolume::SELECTED_OUTSIDE_COLOR[4] = { 0.19f, 0.58f, 1.0f, 1.0f };
 const float GLVolume::DISABLED_COLOR[4] = { 0.25f, 0.25f, 0.25f, 1.0f };
+const float GLVolume::SLA_SUPPORT_COLOR[4] = { 0.75f, 0.75f, 0.75f, 1.0f };
+const float GLVolume::SLA_PAD_COLOR[4] = { 0.0f, 0.2f, 0.0f, 1.0f };
 
 GLVolume::GLVolume(float r, float g, float b, float a)
 #if ENABLE_MODELVOLUME_TRANSFORM
@@ -214,6 +216,7 @@ GLVolume::GLVolume(float r, float g, float b, float a)
     , m_world_matrix_dirty(true)
     , m_transformed_bounding_box_dirty(true)
 #endif // ENABLE_MODELVOLUME_TRANSFORM
+    , m_sla_shift_z(0.0)
     , m_transformed_convex_hull_bounding_box_dirty(true)
     , m_convex_hull(nullptr)
     , m_convex_hull_owned(false)
@@ -378,7 +381,14 @@ void GLVolume::set_convex_hull(const TriangleMesh *convex_hull, bool owned)
     m_convex_hull_owned = owned;
 }
 
-#if !ENABLE_MODELVOLUME_TRANSFORM
+#if ENABLE_MODELVOLUME_TRANSFORM
+Transform3d GLVolume::world_matrix() const
+{
+    Transform3d m = m_instance_transformation.get_matrix() * m_volume_transformation.get_matrix();
+    m.translation()(2) += m_sla_shift_z;
+    return m;
+}
+#else
 const Transform3f& GLVolume::world_matrix() const
 {
     if (m_world_matrix_dirty)
@@ -388,7 +398,7 @@ const Transform3f& GLVolume::world_matrix() const
     }
     return m_world_matrix;
 }
-#endif // !ENABLE_MODELVOLUME_TRANSFORM
+#endif // ENABLE_MODELVOLUME_TRANSFORM
 
 const BoundingBoxf3& GLVolume::transformed_bounding_box() const
 {
@@ -745,18 +755,9 @@ int GLVolumeCollection::load_object_volume(
         { 0.5f, 0.5f, 1.0f, 1.f }
     };
 
-    const ModelVolume *model_volume = model_object->volumes[volume_idx];
-
-    int extruder_id = -1;
-    if (model_volume->is_model_part())
-    {
-        const ConfigOption *opt = model_volume->config.option("extruder");
-        if (opt == nullptr)
-            opt = model_object->config.option("extruder");
-        extruder_id = (opt == nullptr) ? 0 : opt->getInt();
-    }
-
-    const ModelInstance *instance = model_object->instances[instance_idx];
+    const ModelVolume   *model_volume = model_object->volumes[volume_idx];
+    const int            extruder_id  = model_volume->extruder_id();
+    const ModelInstance *instance     = model_object->instances[instance_idx];
 #if ENABLE_MODELVOLUME_TRANSFORM
     const TriangleMesh& mesh = model_volume->mesh;
 #else
@@ -822,21 +823,17 @@ void GLVolumeCollection::load_object_auxiliary(
     bool                            use_VBOs)
 {
     assert(print_object->is_step_done(milestone));
+    Transform3d  mesh_trafo_inv = print_object->trafo().inverse();
     // Get the support mesh.
-    TriangleMesh mesh;
-    switch (milestone) {
-    case slaposSupportTree: mesh = print_object->support_mesh(); break;
-    case slaposBasePool:    mesh = print_object->pad_mesh();     break;
-    default:
-        assert(false);
-    }
+    TriangleMesh mesh = print_object->get_mesh(milestone);
+    mesh.transform(mesh_trafo_inv);
 	// Convex hull is required for out of print bed detection.
 	TriangleMesh convex_hull = mesh.convex_hull_3d();
+    convex_hull.transform(mesh_trafo_inv);
     for (const std::pair<size_t, size_t> &instance_idx : instances) {
         const ModelInstance            &model_instance = *print_object->model_object()->instances[instance_idx.first];
         const SLAPrintObject::Instance &print_instance = print_object->instances()[instance_idx.second];
-        float color[4] { 0.f, 0.f, 1.f, 1.f };
-        this->volumes.emplace_back(new GLVolume(color));
+        this->volumes.emplace_back(new GLVolume((milestone == slaposBasePool) ? GLVolume::SLA_PAD_COLOR : GLVolume::SLA_SUPPORT_COLOR));
         GLVolume &v = *this->volumes.back();
         if (use_VBOs)
             v.indexed_vertex_array.load_mesh_full_shading(mesh);
@@ -845,13 +842,12 @@ void GLVolumeCollection::load_object_auxiliary(
         // finalize_geometry() clears the vertex arrays, therefore the bounding box has to be computed before finalize_geometry().
         v.bounding_box = v.indexed_vertex_array.bounding_box();
         v.indexed_vertex_array.finalize_geometry(use_VBOs);
-		v.composite_id = GLVolume::CompositeID(obj_idx, -1, (int)instance_idx.first);
+        v.composite_id = GLVolume::CompositeID(obj_idx, -milestone, (int)instance_idx.first);
         v.geometry_id = std::pair<size_t, size_t>(timestamp, model_instance.id().id);
 		// Create a copy of the convex hull mesh for each instance. Use a move operator on the last instance.
 		v.set_convex_hull((&instance_idx == &instances.back()) ? new TriangleMesh(std::move(convex_hull)) : new TriangleMesh(convex_hull), true);
         v.is_modifier  = false;
         v.shader_outside_printer_detection_enabled = true;
-        //FIXME adjust with print_instance?
 		v.set_instance_transformation(model_instance.get_transformation());
 		// Leave the volume transformation at identity.
         // v.set_volume_transformation(model_volume->get_transformation());
@@ -1106,7 +1102,7 @@ void GLVolumeCollection::update_colors_by_extruder(const DynamicPrintConfig* con
 
     for (GLVolume* volume : volumes)
     {
-        if ((volume == nullptr) || volume->is_modifier || volume->is_wipe_tower)
+        if ((volume == nullptr) || volume->is_modifier || volume->is_wipe_tower || (volume->volume_idx() < 0))
             continue;
 
         int extruder_id = volume->extruder_id - 1;
diff --git a/src/slic3r/GUI/3DScene.hpp b/src/slic3r/GUI/3DScene.hpp
index 28541cea2..eb6bb9311 100644
--- a/src/slic3r/GUI/3DScene.hpp
+++ b/src/slic3r/GUI/3DScene.hpp
@@ -253,6 +253,8 @@ public:
     static const float OUTSIDE_COLOR[4];
     static const float SELECTED_OUTSIDE_COLOR[4];
     static const float DISABLED_COLOR[4];
+    static const float SLA_SUPPORT_COLOR[4];
+    static const float SLA_PAD_COLOR[4];
 
     GLVolume(float r = 1.f, float g = 1.f, float b = 1.f, float a = 1.f);
     GLVolume(const float *rgba) : GLVolume(rgba[0], rgba[1], rgba[2], rgba[3]) {}
@@ -276,6 +278,8 @@ private:
     // Whether or not is needed to recalculate the world matrix.
     mutable bool          m_world_matrix_dirty;
 #endif // ENABLE_MODELVOLUME_TRANSFORM
+    // Shift in z required by sla supports+pad
+    double m_sla_shift_z;
     // Bounding box of this volume, in unscaled coordinates.
     mutable BoundingBoxf3 m_transformed_bounding_box;
     // Whether or not is needed to recalculate the transformed bounding box.
@@ -424,6 +428,9 @@ public:
     const Vec3d& get_offset() const;
     void set_offset(const Vec3d& offset);
 #endif // ENABLE_MODELVOLUME_TRANSFORM
+     
+    double get_sla_shift_z() const { return m_sla_shift_z; }
+    void set_sla_shift_z(double z) { m_sla_shift_z = z; }
 
     void set_convex_hull(const TriangleMesh *convex_hull, bool owned);
 
@@ -432,7 +439,7 @@ public:
     int                 instance_idx() const { return this->composite_id.instance_id; }
 
 #if ENABLE_MODELVOLUME_TRANSFORM
-    Transform3d world_matrix() const { return m_instance_transformation.get_matrix() * m_volume_transformation.get_matrix(); }
+    Transform3d world_matrix() const;
 #else
     const Transform3f&   world_matrix() const;
 #endif // ENABLE_MODELVOLUME_TRANSFORM
diff --git a/src/slic3r/GUI/GLCanvas3D.cpp b/src/slic3r/GUI/GLCanvas3D.cpp
index 17959af03..f4fc163a0 100644
--- a/src/slic3r/GUI/GLCanvas3D.cpp
+++ b/src/slic3r/GUI/GLCanvas3D.cpp
@@ -1075,7 +1075,6 @@ GLCanvas3D::Selection::VolumeCache::TransformCache::TransformCache()
     , scaling_factor(Vec3d::Ones())
     , rotation_matrix(Transform3d::Identity())
     , scale_matrix(Transform3d::Identity())
-    , no_position_matrix(Transform3d::Identity())
 {
 }
 
@@ -1086,7 +1085,6 @@ GLCanvas3D::Selection::VolumeCache::TransformCache::TransformCache(const Geometr
 {
     rotation_matrix = Geometry::assemble_transform(Vec3d::Zero(), rotation);
     scale_matrix = Geometry::assemble_transform(Vec3d::Zero(), Vec3d::Zero(), scaling_factor);
-    no_position_matrix = transform.get_matrix(true);
 }
 
 GLCanvas3D::Selection::VolumeCache::VolumeCache(const Geometry::Transformation& volume_transform, const Geometry::Transformation& instance_transform)
@@ -1456,7 +1454,7 @@ void GLCanvas3D::Selection::translate(const Vec3d& displacement)
             (*m_volumes)[i]->set_instance_offset(m_cache.volumes_data[i].get_instance_position() + displacement);
         else if (m_mode == Volume)
         {
-            Vec3d local_displacement = (m_cache.volumes_data[i].get_instance_no_position_matrix() * m_cache.volumes_data[i].get_volume_no_position_matrix()).inverse() * displacement;
+            Vec3d local_displacement = (m_cache.volumes_data[i].get_instance_rotation_matrix() * m_cache.volumes_data[i].get_volume_rotation_matrix()).inverse() * displacement;
             (*m_volumes)[i]->set_volume_offset(m_cache.volumes_data[i].get_volume_position() + local_displacement);
         }
 #else
@@ -1940,7 +1938,14 @@ void GLCanvas3D::Selection::_update_type()
             if (m_cache.content.size() == 1) // single object
             {
                 const ModelObject* model_object = m_model->objects[m_cache.content.begin()->first];
-                unsigned int volumes_count = (unsigned int)model_object->volumes.size();
+                unsigned int model_volumes_count = (unsigned int)model_object->volumes.size();
+                unsigned int sla_volumes_count = 0;
+                for (unsigned int i : m_list)
+                {
+                    if ((*m_volumes)[i]->volume_idx() < 0)
+                        ++sla_volumes_count;
+                }
+                unsigned int volumes_count = model_volumes_count + sla_volumes_count;
                 unsigned int instances_count = (unsigned int)model_object->instances.size();
                 unsigned int selected_instances_count = (unsigned int)m_cache.content.begin()->second.size();
                 if (volumes_count * instances_count == (unsigned int)m_list.size())
@@ -2659,6 +2664,43 @@ bool GLCanvas3D::Gizmos::is_running() const
     return (curr != nullptr) ? (curr->get_state() == GLGizmoBase::On) : false;
 }
 
+#if ENABLE_GIZMOS_SHORTCUT
+bool GLCanvas3D::Gizmos::handle_shortcut(int key, const Selection& selection)
+{
+    if (!m_enabled)
+        return false;
+
+    bool handled = false;
+    for (GizmosMap::iterator it = m_gizmos.begin(); it != m_gizmos.end(); ++it)
+    {
+        if ((it->second == nullptr) || !it->second->is_selectable())
+            continue;
+
+        int it_key = it->second->get_shortcut_key();
+
+        if (it->second->is_activable(selection) && ((it_key == key - 64) || (it_key == key - 96)))
+        {
+            if ((it->second->get_state() == GLGizmoBase::On))
+            {
+                it->second->set_state(GLGizmoBase::Off);
+                m_current = Undefined;
+                handled = true;
+            }
+            else if ((it->second->get_state() == GLGizmoBase::Off))
+            {
+                it->second->set_state(GLGizmoBase::On);
+                m_current = it->first;
+                handled = true;
+            }
+        }
+        else
+            it->second->set_state(GLGizmoBase::Off);
+    }
+
+    return handled;
+}
+#endif // ENABLE_GIZMOS_SHORTCUT
+
 bool GLCanvas3D::Gizmos::is_dragging() const
 {
     if (!m_enabled)
@@ -3800,12 +3842,13 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
 
     struct ModelVolumeState {
         ModelVolumeState(const GLVolume *volume) : 
-			geometry_id(volume->geometry_id), volume_idx(-1) {}
-		ModelVolumeState(const ModelID &volume_id, const ModelID &instance_id, const GLVolume::CompositeID &composite_id) :
-			geometry_id(std::make_pair(volume_id.id, instance_id.id)), composite_id(composite_id), volume_idx(-1) {}
+			model_volume(nullptr), geometry_id(volume->geometry_id), volume_idx(-1) {}
+		ModelVolumeState(const ModelVolume *model_volume, const ModelID &instance_id, const GLVolume::CompositeID &composite_id) :
+			model_volume(model_volume), geometry_id(std::make_pair(model_volume->id().id, instance_id.id)), composite_id(composite_id), volume_idx(-1) {}
 		ModelVolumeState(const ModelID &volume_id, const ModelID &instance_id) :
-			geometry_id(std::make_pair(volume_id.id, instance_id.id)), volume_idx(-1) {}
+			model_volume(nullptr), geometry_id(std::make_pair(volume_id.id, instance_id.id)), volume_idx(-1) {}
 		bool new_geometry() const { return this->volume_idx == size_t(-1); }
+		const ModelVolume		   *model_volume;
         // ModelID of ModelVolume + ModelID of ModelInstance
         // or timestamp of an SLAPrintObjectStep + ModelID of ModelInstance
         std::pair<size_t, size_t>   geometry_id;
@@ -3844,7 +3887,7 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
                 const ModelInstance *model_instance = model_object->instances[instance_idx];
                 for (int volume_idx = 0; volume_idx < (int)model_object->volumes.size(); ++ volume_idx) {
                     const ModelVolume *model_volume = model_object->volumes[volume_idx];
-					model_volume_state.emplace_back(model_volume->id(), model_instance->id(), GLVolume::CompositeID(object_idx, volume_idx, instance_idx));
+					model_volume_state.emplace_back(model_volume, model_instance->id(), GLVolume::CompositeID(object_idx, volume_idx, instance_idx));
                 }
             }
         }
@@ -3894,9 +3937,16 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
                     delete volume;
             } else {
                 // This GLVolume will be reused.
+                volume->set_sla_shift_z(0.0);
                 map_glvolume_old_to_new[volume_id] = glvolumes_new.size();
                 mvs->volume_idx = glvolumes_new.size();
                 glvolumes_new.emplace_back(volume);
+                // Update color of the volume based on the current extruder.
+				if (mvs->model_volume != nullptr) {
+					int extruder_id = mvs->model_volume->extruder_id();
+					if (extruder_id != -1)
+						volume->extruder_id = extruder_id;
+				}
             }
         }
     }
@@ -3998,7 +4048,7 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
                                 instances[istep].emplace_back(std::pair<size_t, size_t>(instance_idx, print_instance_idx));
                             else
 								// Recycling an old GLVolume. Update the Object/Instance indices into the current Model.
-                                m_volumes.volumes[it->volume_idx]->composite_id = GLVolume::CompositeID(object_idx, -1, instance_idx);
+                                m_volumes.volumes[it->volume_idx]->composite_id = GLVolume::CompositeID(object_idx, m_volumes.volumes[it->volume_idx]->volume_idx(), instance_idx);
                         }
                 }
 
@@ -4013,11 +4063,11 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
                 {
                     // If any volume has been added
                     // Shift-up all volumes of the object so that it has the right elevation with respect to the print bed
-                    Vec3d shift_z(0.0, 0.0, print_object->get_elevation());
+                    double shift_z = print_object->get_elevation();
                     for (GLVolume* volume : m_volumes.volumes)
                     {
                         if (volume->object_idx() == object_idx)
-                            volume->set_instance_offset(volume->get_instance_offset() + shift_z);
+                            volume->set_sla_shift_z(shift_z);
                     }
                 }
             }
@@ -4273,7 +4323,16 @@ void GLCanvas3D::on_char(wxKeyEvent& evt)
 #endif // ENABLE_MODIFIED_CAMERA_TARGET
                 default:
                 {
-                    evt.Skip();
+#if ENABLE_GIZMOS_SHORTCUT
+                    if (m_gizmos.handle_shortcut(keyCode, m_selection))
+                    {
+                        _update_gizmos_data();
+                        render();
+                    }
+                    else
+#endif // ENABLE_GIZMOS_SHORTCUT
+                        evt.Skip();
+
                     break;
                 }
                 }
@@ -4761,16 +4820,14 @@ void GLCanvas3D::on_key_down(wxKeyEvent& evt)
     else
     {
         int key = evt.GetKeyCode();
+#ifdef __WXOSX__
+        if (key == WXK_BACK)
+#else
         if (key == WXK_DELETE)
+#endif // __WXOSX__
             post_event(SimpleEvent(EVT_GLCANVAS_REMOVE_OBJECT));
         else
-		{
-#ifdef __WXOSX__
-			if (key == WXK_BACK)
-                post_event(SimpleEvent(EVT_GLCANVAS_REMOVE_OBJECT));
-#endif
-			evt.Skip();
-		}
+            evt.Skip();
     }
 }
 
diff --git a/src/slic3r/GUI/GLCanvas3D.hpp b/src/slic3r/GUI/GLCanvas3D.hpp
index 5404701f8..7dac13d72 100644
--- a/src/slic3r/GUI/GLCanvas3D.hpp
+++ b/src/slic3r/GUI/GLCanvas3D.hpp
@@ -384,7 +384,6 @@ public:
                 Vec3d scaling_factor;
                 Transform3d rotation_matrix;
                 Transform3d scale_matrix;
-                Transform3d no_position_matrix;
 
                 TransformCache();
                 explicit TransformCache(const Geometry::Transformation& transform);
@@ -415,14 +414,12 @@ public:
             const Vec3d& get_volume_scaling_factor() const { return m_volume.scaling_factor; }
             const Transform3d& get_volume_rotation_matrix() const { return m_volume.rotation_matrix; }
             const Transform3d& get_volume_scale_matrix() const { return m_volume.scale_matrix; }
-            const Transform3d& get_volume_no_position_matrix() const { return m_volume.no_position_matrix; }
 
             const Vec3d& get_instance_position() const { return m_instance.position; }
             const Vec3d& get_instance_rotation() const { return m_instance.rotation; }
             const Vec3d& get_instance_scaling_factor() const { return m_instance.scaling_factor; }
             const Transform3d& get_instance_rotation_matrix() const { return m_instance.rotation_matrix; }
             const Transform3d& get_instance_scale_matrix() const { return m_instance.scale_matrix; }
-            const Transform3d& get_instance_no_position_matrix() const { return m_instance.no_position_matrix; }
 #else
             const Vec3d& get_position() const { return m_position; }
             const Vec3d& get_rotation() const { return m_rotation; }
@@ -611,6 +608,9 @@ private:
         EType get_current_type() const;
 
         bool is_running() const;
+#if ENABLE_GIZMOS_SHORTCUT
+        bool handle_shortcut(int key, const Selection& selection);
+#endif // ENABLE_GIZMOS_SHORTCUT
 
         bool is_dragging() const;
         void start_dragging(const Selection& selection);
diff --git a/src/slic3r/GUI/GLGizmo.cpp b/src/slic3r/GUI/GLGizmo.cpp
index 906e064e0..40c1f09fe 100644
--- a/src/slic3r/GUI/GLGizmo.cpp
+++ b/src/slic3r/GUI/GLGizmo.cpp
@@ -30,6 +30,10 @@
 #include "GUI_Utils.hpp"
 #include "GUI_App.hpp"
 
+#if ENABLE_GIZMOS_SHORTCUT
+#include <wx/defs.h>
+#endif // ENABLE_GIZMOS_SHORTCUT
+
 // TODO: Display tooltips quicker on Linux
 
 static const float DEFAULT_BASE_COLOR[3] = { 0.625f, 0.625f, 0.625f };
@@ -161,6 +165,9 @@ GLGizmoBase::GLGizmoBase(GLCanvas3D& parent)
     : m_parent(parent)
     , m_group_id(-1)
     , m_state(Off)
+#if ENABLE_GIZMOS_SHORTCUT
+    , m_shortcut_key(0)
+#endif // ENABLE_GIZMOS_SHORTCUT
     , m_hover_id(-1)
     , m_dragging(false)
 {
@@ -639,6 +646,10 @@ bool GLGizmoRotate3D::on_init()
     if (!m_textures[On].load_from_file(path + "rotate_on.png", false))
         return false;
 
+#if ENABLE_GIZMOS_SHORTCUT
+    m_shortcut_key = WXK_CONTROL_R;
+#endif // ENABLE_GIZMOS_SHORTCUT
+
     return true;
 }
 
@@ -713,6 +724,10 @@ bool GLGizmoScale3D::on_init()
     m_grabbers[2].angles(0) = half_pi;
     m_grabbers[3].angles(0) = half_pi;
 
+#if ENABLE_GIZMOS_SHORTCUT
+    m_shortcut_key = WXK_CONTROL_S;
+#endif // ENABLE_GIZMOS_SHORTCUT
+
     return true;
 }
 
@@ -1057,6 +1072,10 @@ bool GLGizmoMove3D::on_init()
         m_grabbers.push_back(Grabber());
     }
 
+#if ENABLE_GIZMOS_SHORTCUT
+    m_shortcut_key = WXK_CONTROL_M;
+#endif // ENABLE_GIZMOS_SHORTCUT
+
     return true;
 }
 
@@ -1213,6 +1232,10 @@ bool GLGizmoFlatten::on_init()
     if (!m_textures[On].load_from_file(path + "layflat_on.png", false))
         return false;
 
+#if ENABLE_GIZMOS_SHORTCUT
+    m_shortcut_key = WXK_CONTROL_F;
+#endif // ENABLE_GIZMOS_SHORTCUT
+
     return true;
 }
 
@@ -1542,6 +1565,10 @@ bool GLGizmoSlaSupports::on_init()
     if (!m_textures[On].load_from_file(path + "sla_support_points_on.png", false))
         return false;
 
+#if ENABLE_GIZMOS_SHORTCUT
+    m_shortcut_key = WXK_CONTROL_L;
+#endif // ENABLE_GIZMOS_SHORTCUT
+
     return true;
 }
 
@@ -1893,6 +1920,10 @@ bool GLGizmoCut::on_init()
 
     m_grabbers.emplace_back();
 
+#if ENABLE_GIZMOS_SHORTCUT
+    m_shortcut_key = WXK_CONTROL_C;
+#endif // ENABLE_GIZMOS_SHORTCUT
+
     return true;
 }
 
diff --git a/src/slic3r/GUI/GLGizmo.hpp b/src/slic3r/GUI/GLGizmo.hpp
index 647d870e4..a8073bd78 100644
--- a/src/slic3r/GUI/GLGizmo.hpp
+++ b/src/slic3r/GUI/GLGizmo.hpp
@@ -77,6 +77,9 @@ protected:
 
     int m_group_id;
     EState m_state;
+#if ENABLE_GIZMOS_SHORTCUT
+    int m_shortcut_key;
+#endif // ENABLE_GIZMOS_SHORTCUT
     // textures are assumed to be square and all with the same size in pixels, no internal check is done
     GLTexture m_textures[Num_States];
     int m_hover_id;
@@ -100,6 +103,11 @@ public:
     EState get_state() const { return m_state; }
     void set_state(EState state) { m_state = state; on_set_state(); }
 
+#if ENABLE_GIZMOS_SHORTCUT
+    int get_shortcut_key() const { return m_shortcut_key; }
+    void set_shortcut_key(int key) { m_shortcut_key = key; }
+#endif // ENABLE_GIZMOS_SHORTCUT
+
     bool is_activable(const GLCanvas3D::Selection& selection) const { return on_is_activable(selection); }
     bool is_selectable() const { return on_is_selectable(); }
 
diff --git a/src/slic3r/GUI/GUI_ObjectList.cpp b/src/slic3r/GUI/GUI_ObjectList.cpp
index da358670b..3cfcdad0f 100644
--- a/src/slic3r/GUI/GUI_ObjectList.cpp
+++ b/src/slic3r/GUI/GUI_ObjectList.cpp
@@ -25,6 +25,7 @@ ObjectList::ObjectList(wxWindow* parent) :
 {
     // Fill CATEGORY_ICON
     {
+        // ptFFF
 		CATEGORY_ICON[L("Layers and Perimeters")]	= wxBitmap(from_u8(var("layers.png")), wxBITMAP_TYPE_PNG);
 		CATEGORY_ICON[L("Infill")]					= wxBitmap(from_u8(var("infill.png")), wxBITMAP_TYPE_PNG);
 		CATEGORY_ICON[L("Support material")]		= wxBitmap(from_u8(var("building.png")), wxBITMAP_TYPE_PNG);
@@ -34,6 +35,9 @@ ObjectList::ObjectList(wxWindow* parent) :
 // 		CATEGORY_ICON[L("Skirt and brim")]			= wxBitmap(from_u8(var("box.png")), wxBITMAP_TYPE_PNG);
 // 		CATEGORY_ICON[L("Speed > Acceleration")]	= wxBitmap(from_u8(var("time.png")), wxBITMAP_TYPE_PNG);
 		CATEGORY_ICON[L("Advanced")]				= wxBitmap(from_u8(var("wand.png")), wxBITMAP_TYPE_PNG);
+		// ptSLA
+		CATEGORY_ICON[L("Supports")]				= wxBitmap(from_u8(var("building.png")), wxBITMAP_TYPE_PNG);
+		CATEGORY_ICON[L("Pad")]				        = wxBitmap(from_u8(var("brick.png")), wxBITMAP_TYPE_PNG);
     }
 
     // create control
@@ -310,8 +314,8 @@ void ObjectList::show_context_menu()
         if (!(m_objects_model->GetItemType(item) & (itObject | itVolume)))
             return;
         const auto menu = m_objects_model->GetParent(item) == wxDataViewItem(0) ?
-            create_add_part_popupmenu() :
-            create_part_settings_popupmenu();
+            create_object_popupmenu() :
+            create_part_popupmenu();
         wxGetApp().tab_panel()->GetPage(0)->PopupMenu(menu);
     }
 }
@@ -436,6 +440,13 @@ void ObjectList::on_drop(wxDataViewEvent &event)
 
 std::vector<std::string> get_options(const bool is_part)
 {
+    if (wxGetApp().plater()->printer_technology() == ptSLA) {
+        SLAPrintObjectConfig full_sla_config;
+        auto options = full_sla_config.keys();
+        options.erase(find(options.begin(), options.end(), "layer_height"));
+        return options;
+    }
+
     PrintRegionConfig reg_config;
     auto options = reg_config.keys();
     if (!is_part) {
@@ -463,7 +474,10 @@ void get_options_menu(settings_menu_hierarchy& settings_menu, bool is_part)
         if (category.empty() ||
             (category == "Extruders" && extruders_cnt == 1)) continue;
 
-        std::pair<std::string, std::string> option_label(option, opt->label);
+        const std::string& label = opt->label.empty() ? opt->full_label : 
+                                   opt->full_label.empty() ? opt->label :
+                                   opt->full_label + " " + opt->label;;
+        std::pair<std::string, std::string> option_label(option, label);
         std::vector< std::pair<std::string, std::string> > new_category;
         auto& cat_opt_label = settings_menu.find(category) == settings_menu.end() ? new_category : settings_menu.at(category);
         cat_opt_label.push_back(option_label);
@@ -575,14 +589,27 @@ wxMenuItem* ObjectList::menu_item_settings(wxMenu* menu, int id, const bool is_p
     auto  menu_item = new wxMenuItem(menu, id, _(L("Add settings")));
     menu_item->SetBitmap(m_bmp_cog);
 
-    auto sub_menu = create_add_settings_popupmenu(is_part);
+    auto sub_menu = create_settings_popupmenu(is_part);
     menu_item->SetSubMenu(sub_menu);
     return menu_item;
 }
 
-wxMenu* ObjectList::create_add_part_popupmenu()
+wxMenu* ObjectList::create_object_popupmenu()
 {
     wxMenu *menu = new wxMenu;
+    if (wxGetApp().plater()->printer_technology() == ptSLA)
+    {
+        wxWindowID config_id_base = NewControlId(1);
+        // Append settings popupmenu
+        menu->Append(menu_item_settings(menu, config_id_base, false));
+
+        menu->Bind(wxEVT_MENU, [menu, this](wxEvent &event) {
+            get_settings_choice(menu, event.GetId(), false);
+        });
+
+        return menu;
+    }
+
     // Note: id accords to type of the sub-object, so sequence of the menu items is important
     std::vector<std::string> menu_object_types_items = {L("Add part"),              // ~ModelVolume::MODEL_PART
                                                         L("Add modifier"),          // ~ModelVolume::PARAMETER_MODIFIER
@@ -635,7 +662,7 @@ wxMenu* ObjectList::create_add_part_popupmenu()
     return menu;
 }
 
-wxMenu* ObjectList::create_part_settings_popupmenu()
+wxMenu* ObjectList::create_part_popupmenu()
 {
     wxMenu *menu = new wxMenu;
     wxWindowID config_id_base = NewControlId(3);
@@ -671,7 +698,7 @@ wxMenu* ObjectList::create_part_settings_popupmenu()
     return menu;
 }
 
-wxMenu* ObjectList::create_add_settings_popupmenu(bool is_part)
+wxMenu* ObjectList::create_settings_popupmenu(bool is_part)
 {
     wxMenu *menu = new wxMenu;
 
diff --git a/src/slic3r/GUI/GUI_ObjectList.hpp b/src/slic3r/GUI/GUI_ObjectList.hpp
index 31ae5f5ed..862e0237b 100644
--- a/src/slic3r/GUI/GUI_ObjectList.hpp
+++ b/src/slic3r/GUI/GUI_ObjectList.hpp
@@ -98,9 +98,9 @@ public:
     void                menu_item_add_generic(wxMenuItem* &menu, int id, const int type);
     wxMenuItem*         menu_item_split(wxMenu* menu, int id);
     wxMenuItem*         menu_item_settings(wxMenu* menu, int id, const bool is_part);
-    wxMenu*             create_add_part_popupmenu();
-    wxMenu*             create_part_settings_popupmenu();
-    wxMenu*             create_add_settings_popupmenu(bool is_part);
+    wxMenu*             create_object_popupmenu();
+    wxMenu*             create_part_popupmenu();
+    wxMenu*             create_settings_popupmenu(bool is_part);
 
     void                load_subobject(int type);
     void                load_part(ModelObject* model_object, wxArrayString& part_names, int type);
diff --git a/src/slic3r/GUI/MainFrame.cpp b/src/slic3r/GUI/MainFrame.cpp
index b0d0c178b..608c78e0e 100644
--- a/src/slic3r/GUI/MainFrame.cpp
+++ b/src/slic3r/GUI/MainFrame.cpp
@@ -211,6 +211,11 @@ bool MainFrame::can_delete() const
 {
     return (m_plater != nullptr) ? !m_plater->is_selection_empty() : false;
 }
+
+bool MainFrame::can_delete_all() const
+{
+    return (m_plater != nullptr) ? !m_plater->model().objects.empty() : false;
+}
 #endif // ENABLE_NEW_MENU_LAYOUT
 
 void MainFrame::init_menubar()
@@ -319,11 +324,15 @@ void MainFrame::init_menubar()
         editMenu = new wxMenu();
         wxMenuItem* item_select_all = append_menu_item(editMenu, wxID_ANY, L("Select all\tCtrl+A"), L("Selects all objects"),
             [this](wxCommandEvent&) { m_plater->select_all(); }, "");
+        editMenu->AppendSeparator();
         wxMenuItem* item_delete_sel = append_menu_item(editMenu, wxID_ANY, L("Delete selected\tDel"), L("Deletes the current selection"),
             [this](wxCommandEvent&) { m_plater->remove_selected(); }, "");
+        wxMenuItem* item_delete_all = append_menu_item(editMenu, wxID_ANY, L("Delete all\tCtrl+Del"), L("Deletes all objects"),
+            [this](wxCommandEvent&) { m_plater->reset(); }, "");
 
         Bind(wxEVT_UPDATE_UI, [this](wxUpdateUIEvent& evt) { evt.Enable(can_select()); }, item_select_all->GetId());
         Bind(wxEVT_UPDATE_UI, [this](wxUpdateUIEvent& evt) { evt.Enable(can_delete()); }, item_delete_sel->GetId());
+        Bind(wxEVT_UPDATE_UI, [this](wxUpdateUIEvent& evt) { evt.Enable(can_delete_all()); }, item_delete_all->GetId());
     }
 #endif // ENABLE_NEW_MENU_LAYOUT
 
diff --git a/src/slic3r/GUI/MainFrame.hpp b/src/slic3r/GUI/MainFrame.hpp
index 488d0bd04..2ee46cbb1 100644
--- a/src/slic3r/GUI/MainFrame.hpp
+++ b/src/slic3r/GUI/MainFrame.hpp
@@ -73,6 +73,7 @@ class MainFrame : public wxFrame
     bool can_change_view() const;
     bool can_select() const;
     bool can_delete() const;
+    bool can_delete_all() const;
 #endif // ENABLE_NEW_MENU_LAYOUT
 
 public:
diff --git a/src/slic3r/GUI/Plater.cpp b/src/slic3r/GUI/Plater.cpp
index f3b3318db..0dcc61542 100644
--- a/src/slic3r/GUI/Plater.cpp
+++ b/src/slic3r/GUI/Plater.cpp
@@ -1771,9 +1771,7 @@ unsigned int Plater::priv::update_background_process()
             }
             break;
         case ptSLA:
-            //FIXME as of now the Print::APPLY_STATUS_INVALIDATED is not reliable, and
-            // currently the scene refresh is expensive and loses selection.
-            //return_state |= UPDATE_BACKGROUND_PROCESS_REFRESH_SCENE;
+            return_state |= UPDATE_BACKGROUND_PROCESS_REFRESH_SCENE;
             break;
         }
     }
@@ -1984,13 +1982,8 @@ void Plater::priv::on_process_completed(wxCommandEvent &evt)
     case ptSLA:
         // Update the SLAPrint from the current Model, so that the reload_scene()
         // pulls the correct data.
-
-        // FIXME: SLAPrint::apply is not ready for this. At this stage it would
-        // invalidate the previous result and the supports would not be available
-        // for rendering.
-//        if (this->update_background_process() & UPDATE_BACKGROUND_PROCESS_RESTART)
-//            this->schedule_background_process();
-
+        if (this->update_background_process() & UPDATE_BACKGROUND_PROCESS_RESTART)
+            this->schedule_background_process();
         _3DScene::reload_scene(canvas3D, true);
         break;
     }
@@ -2281,6 +2274,8 @@ void Plater::select_view(const std::string& direction) { p->select_view(directio
 void Plater::select_all() { p->select_all(); }
 
 void Plater::remove(size_t obj_idx) { p->remove(obj_idx); }
+void Plater::reset() { p->reset(); }
+
 void Plater::delete_object_from_model(size_t obj_idx) { p->delete_object_from_model(obj_idx); }
 
 void Plater::remove_selected()
diff --git a/src/slic3r/GUI/Plater.hpp b/src/slic3r/GUI/Plater.hpp
index b9cc9d528..5a5585935 100644
--- a/src/slic3r/GUI/Plater.hpp
+++ b/src/slic3r/GUI/Plater.hpp
@@ -130,6 +130,7 @@ public:
 
     void select_all();
     void remove(size_t obj_idx);
+    void reset();
     void delete_object_from_model(size_t obj_idx);
     void remove_selected();
     void increase_instances(size_t num = 1);
diff --git a/src/slic3r/GUI/Tab.cpp b/src/slic3r/GUI/Tab.cpp
index 85220b8ad..2cc24eca5 100644
--- a/src/slic3r/GUI/Tab.cpp
+++ b/src/slic3r/GUI/Tab.cpp
@@ -3011,6 +3011,7 @@ void TabSLAPrint::build()
     optgroup->append_single_option_line("support_critical_angle");
     optgroup->append_single_option_line("support_max_bridge_length");
 
+    page = add_options_page(_(L("Pad")), "brick.png");
     optgroup = page->new_optgroup(_(L("Pad")));
     optgroup->append_single_option_line("pad_enable");
     optgroup->append_single_option_line("pad_wall_thickness");