Scale to Fit Print Volume: fit the area every nozzle reaches

Each nozzle reaches only part of the bed on a multi-nozzle printer (H2D:
left 0-325, right 25-350 in X), but the command fitted the whole 350 mm
bed. A model that filled the bed in X therefore landed outside both
nozzles' printable range, and right after the user asked to fit it the
plater warned "The position or size of the model exceeds the right
nozzle's printable range".

Fit the volume every nozzle shares instead -- the same region Arrange
already places items in -- and centre on it rather than on the bed.

src/libslic3r/Arrange.cpp

@@ -122,8 +122,8 @@ void update_arrange_params(ArrangeParams& params, const DynamicPrintConfig* prin
 
 void update_selected_items_inflation(ArrangePolygons& selected, const DynamicPrintConfig* print_cfg, ArrangeParams& params) {
     // do not inflate brim_width. Objects are allowed to have overlapped brim.
-    Points      bedpts = get_shrink_bedpts(print_cfg, params);
-    BoundingBox bedbb = Polygon(bedpts).bounding_box();
+    // A brim reaching the printable area's edge is fine, so measure against the full bed.
+    BoundingBox bedbb = Polygon(get_bed_shape(*print_cfg)).bounding_box();
     // set obj distance for auto seq_print
     if (params.is_seq_print) {
         bool all_objects_are_short = std::all_of(selected.begin(), selected.end(), [&](ArrangePolygon& ap) { return ap.height < params.nozzle_height; });
@@ -144,14 +144,30 @@ void update_selected_items_inflation(ArrangePolygons& selected, const DynamicPri
         // 3. otherwise, use each object's own brim width
         ap.inflation = params.min_obj_distance != 0 ? params.min_obj_distance / 2 :
             plate_has_tree_support ? scaled(brim_max / 2) : scaled(ap.brim_width);
-        BoundingBox apbb = ap.poly.contour.bounding_box();
-        auto        diffx = bedbb.size().x() - apbb.size().x() - 5;
-        auto        diffy = bedbb.size().y() - apbb.size().y() - 5;
-        if (diffx > 0 && diffy > 0) {
-            auto min_diff = std::min(diffx, diffy);
-            ap.inflation = std::min(min_diff / 2, ap.inflation);
-        }
+        if (params.min_obj_distance != 0)
+            return; // an explicit object distance is the user's call, not ours to shrink
+        // An item cannot be larger than the printable area, inflation included. Inflating
+        // an almost bed filling item would leave it too big to ever be placed.
+        BoundingBox apbb   = ap.poly.contour.bounding_box();
+        auto        diffx  = bedbb.size().x() - apbb.size().x();
+        auto        diffy  = bedbb.size().y() - apbb.size().y();
+        ap.inflation = std::max<coord_t>(0, std::min({ ap.inflation, diffx / 2, diffy / 2 }));
         });
+
+    // Give the bed margin, which the arrange bed keeps from the printable area, back
+    // where the largest item needs it. The skirt keeps its room: pushing a skirt off
+    // the bed is worse than saying the item does not fit.
+    if (!selected.empty()) {
+        coord_t max_width = 0, max_height = 0;
+        for (const ArrangePolygon &ap : selected) {
+            BoundingBox apbb = ap.poly.contour.bounding_box();
+            max_width        = std::max(max_width, apbb.size().x() + 2 * ap.inflation);
+            max_height       = std::max(max_height, apbb.size().y() + 2 * ap.inflation);
+        }
+        auto margin = [](coord_t bed, coord_t item) { return std::max(0., unscale<double>(bed - item) / 2.); };
+        params.bed_shrink_x = std::min<double>(params.bed_shrink_x, std::max<double>(params.brim_skirt_distance, margin(bedbb.size().x(), max_width)));
+        params.bed_shrink_y = std::min<double>(params.bed_shrink_y, std::max<double>(params.brim_skirt_distance, margin(bedbb.size().y(), max_height)));
+    }
 }
 
 void update_unselected_items_inflation(ArrangePolygons& unselected, const DynamicPrintConfig* print_cfg, const ArrangeParams& params)

src/libslic3r/LayOnFace.cpp

@@ -213,13 +213,29 @@ int find_plane_at_point(const std::vector<LayOnFacePlane> &planes, const Transfo
     return -1;
 }
 
+Transform3d lay_on_face_rotation(const Vec3d &normal, const Transform3d &instance_matrix_no_offset)
+{
+    // Normal in instance coordinates: a normal transforms by the inverse transpose.
+    const Vec3d tnormal = (instance_matrix_no_offset.matrix().block(0, 0, 3, 3).inverse().transpose() * normal).normalized();
+    const Vec3d down    = -Vec3d::UnitZ();
+
+    // A face already pointing straight up needs a half turn, and every horizontal axis does
+    // that equally well. setFromTwoVectors() resolves the choice through an SVD whose null
+    // space is the whole XY plane, so the axis follows rounding noise and the object lands at
+    // an arbitrary angle in the plate plane. Turn it over about X instead, which keeps the
+    // footprint the object already had.
+    if (tnormal.dot(down) < -1. + 1e-9)
+        return Transform3d(Eigen::AngleAxisd(PI, Vec3d::UnitX()));
+
+    return Transform3d(Eigen::Quaterniond().setFromTwoVectors(tnormal, down));
+}
+
 void lay_on_face(ModelObject &object, size_t instance_idx, const Vec3d &normal)
 {
     ModelInstance                  &instance = *object.instances[instance_idx];
     const Geometry::Transformation &trafo    = instance.get_transformation();
-    // Same rotation as Selection::flattening_rotate(): turn the transformed normal to point down.
-    const Vec3d       tnormal  = trafo.get_matrix().matrix().block(0, 0, 3, 3).inverse().transpose() * normal;
-    const Transform3d rotation = Transform3d(Eigen::Quaterniond().setFromTwoVectors(tnormal, -Vec3d::UnitZ()));
+    // Same rotation as Selection::flattening_rotate(), which the gizmo uses.
+    const Transform3d rotation = lay_on_face_rotation(normal, trafo.get_matrix_no_offset());
     instance.set_transformation(Geometry::Transformation(trafo.get_offset_matrix() * rotation * trafo.get_matrix_no_offset()));
     // Drop this instance only: ensure_on_bed() skips instances without auto_drop and measures the first instance.
     object.translate_instance(instance_idx, -object.instance_bounding_box(instance_idx).min.z() * Vec3d::UnitZ());

src/libslic3r/LayOnFace.hpp

@@ -46,4 +46,10 @@ int find_plane_at_point(const std::vector<LayOnFacePlane> &planes, const Transfo
 // the gizmo applies, then drops the instance so its lowest point is at z = 0.
 void lay_on_face(ModelObject &object, size_t instance_idx, const Vec3d &normal);
 
+// The rotation that turns `normal` (object coordinates) to point down, given the instance's
+// rotation, scale and mirror. A face that already points straight up is turned over about X:
+// the axis setFromTwoVectors() picks there is arbitrary, and it lands the object at a random
+// angle in the plate plane.
+Transform3d lay_on_face_rotation(const Vec3d &normal, const Transform3d &instance_matrix_no_offset);
+
 } // namespace Slic3r

src/slic3r/GUI/Jobs/ArrangeJob.cpp

@@ -771,6 +771,17 @@ void ArrangeJob::finalize(bool canceled, std::exception_ptr &eptr) {
     if (canceled || eptr)
         return;
 
+    // Nothing could be placed: leave the plates and the instances exactly as they were.
+    // Rebuilding the plates would only re-home the instances by their bounds, which moves
+    // a too large item to whichever plate it happens to reach over.
+    const bool nothing_arranged = !m_selected.empty() &&
+        std::all_of(m_selected.begin(), m_selected.end(), [](const ArrangePolygon &ap) { return !ap.is_arranged(); });
+    if (nothing_arranged) {
+        m_plater->get_notification_manager()->close_notification_of_type(NotificationType::ArrangeOngoing);
+        m_plater->m_arrange_running.store(false);
+        return;
+    }
+
     // Unprintable items go to the last virtual bed
     int beds = 0;
 
@@ -870,12 +881,13 @@ void ArrangeJob::finalize(bool canceled, std::exception_ptr &eptr) {
     }
     m_plater->get_notification_manager()->close_notification_of_type(NotificationType::ArrangeOngoing);
 
-    //BBS: reload all objects due to arrange
+    //BBS: reload all objects due to arrange. Plates are never recycled here: arranging
+    // must not remove a plate the user created, even when the arrange left it empty.
     if (only_on_partplate) {
-        plate_list.rebuild_plates_after_arrangement(!only_on_partplate, true, current_plate_index);
+        plate_list.rebuild_plates_after_arrangement(false, true, current_plate_index);
     }
     else {
-        plate_list.rebuild_plates_after_arrangement(!only_on_partplate, true);
+        plate_list.rebuild_plates_after_arrangement(false, true);
     }
 
     // unlock the plates we just locked

src/slic3r/GUI/Jobs/FillBedJob.cpp

@@ -248,7 +248,6 @@ void FillBedJob::process(Ctl &ctl)
     if (m_object_idx == -1 || m_selected.empty()) return;
 
     update_arrange_params(params, m_plater->config(), m_selected);
-    m_bedpts = get_shrink_bedpts(m_plater->config(), params);
 
     auto &partplate_list               = m_plater->get_partplate_list();
     auto &print                        = wxGetApp().plater()->get_partplate_list().get_current_fff_print();
@@ -260,6 +259,8 @@ void FillBedJob::process(Ctl &ctl)
 
     update_selected_items_inflation(m_selected, m_plater->config(), params);
     update_unselected_items_inflation(m_unselected, m_plater->config(), params);
+    // After the inflation, which may give back part of the bed margin.
+    m_bedpts = get_shrink_bedpts(m_plater->config(), params);
 
     bool do_stop = false;
     params.stopcondition = [&ctl, &do_stop]() {

src/slic3r/GUI/PartPlate.cpp

@@ -7048,19 +7048,14 @@ void PartPlateList::postprocess_arrange_polygon(arrangement::ArrangePolygon& arr
 {
 	BOOST_LOG_TRIVIAL(debug) << __FUNCTION__ << boost::format(": bed_idx %1%, selected %2%, translation(x) %3%, (y) %4%") % arrange_polygon.bed_idx % selected % unscale<double>(arrange_polygon.translation(X)) % unscale<double>(arrange_polygon.translation(Y));
 
+	// UNARRANGED means the item could not be placed, so it has no bed to map onto and
+	// must be left where the user had it. Moving it to a virtual bed here would shift
+	// it off the plate, because no such plate is created for it afterwards.
+	if (arrange_polygon.bed_idx == arrangement::UNARRANGED)
+		return;
+
 	if ((selected) || (arrange_polygon.bed_idx != PartPlateList::MAX_PLATES_COUNT))
 	{
-		if (arrange_polygon.bed_idx == -1)
-		{
-			// outarea for large object
-			arrange_polygon.bed_idx = m_plate_list.size();
-			BoundingBox apbox = get_extents(arrange_polygon.transformed_poly());  // the item may have been rotated
-			auto        apbox_size = apbox.size();
-
-			arrange_polygon.translation(X) = 0.5 * apbox_size[0];
-			arrange_polygon.translation(Y) = scaled<double>(static_cast<double>(m_plate_depth)) - 0.5 * apbox_size[1];
-		}
-
 		arrange_polygon.row = arrange_polygon.bed_idx / m_plate_cols;
 		arrange_polygon.col = arrange_polygon.bed_idx % m_plate_cols;
 		arrange_polygon.translation(X) += scaled<double>(plate_stride_x() * arrange_polygon.col);

src/slic3r/GUI/Plater.cpp

@@ -11034,7 +11034,17 @@ void Plater::priv::split_volume()
 void Plater::priv::scale_selection_to_fit_print_volume()
 {
 #if ENABLE_ENHANCED_PRINT_VOLUME_FIT
-    this->view3D->get_canvas3d()->get_selection().scale_to_fit_print_volume(this->bed.build_volume());
+    const BuildVolume volume = this->bed.build_volume();
+    // Every plate shares the bed size, but each sits at its own origin: fit onto the
+    // plate the selection is on instead of always onto the first one.
+    PartPlate*    plate      = this->partplate_list.get_curr_plate();
+    const Vec3d   bed_center = plate != nullptr ? plate->get_center_origin() :
+                                                  Vec3d(volume.bed_center().x(), volume.bed_center().y(), 0.);
+    // On a multi-nozzle printer each nozzle reaches only part of the bed, so a model fitted
+    // to the bed can still exceed a nozzle's printable range. Fit into the volume every
+    // nozzle shares, which is also the area Arrange places items in.
+    const BoundingBoxf3 print_volume = plate != nullptr ? plate->get_build_volume(true) : volume.bounding_volume();
+    this->view3D->get_canvas3d()->get_selection().scale_to_fit_print_volume(volume, Vec2d(bed_center.x(), bed_center.y()), print_volume);
 #else
     this->view3D->get_canvas3d()->get_selection().scale_to_fit_print_volume(*config);
 #endif // ENABLE_ENHANCED_PRINT_VOLUME_FIT

src/slic3r/GUI/Selection.cpp

@@ -17,6 +17,7 @@
 #include "libslic3r/Color.hpp"
 #include "libslic3r/Point.hpp"
 #include "libslic3r/Geometry.hpp"
+#include "libslic3r/LayOnFace.hpp"
 #include "slic3r/GUI/GLModel.hpp"
 #include <string>
 #include <vector>
@@ -1472,11 +1473,9 @@ void Selection::flattening_rotate(const Vec3d& normal)
 
     for (unsigned int i : m_list) {
         GLVolume& v = *(*m_volumes)[i];
-        // Normal transformed from the object coordinate space to the world coordinate space.
+        // Additional rotation to align the face normal with the down vector in the world coordinate space.
         const Geometry::Transformation& old_inst_trafo = v.get_instance_transformation();
-        const Vec3d tnormal = old_inst_trafo.get_matrix().matrix().block(0, 0, 3, 3).inverse().transpose() * normal;
-        // Additional rotation to align tnormal with the down vector in the world coordinate space.
-        const Transform3d rotation_matrix = Transform3d(Eigen::Quaterniond().setFromTwoVectors(tnormal, -Vec3d::UnitZ()));
+        const Transform3d rotation_matrix = lay_on_face_rotation(normal, old_inst_trafo.get_matrix_no_offset());
         v.set_instance_transformation(old_inst_trafo.get_offset_matrix() * rotation_matrix * old_inst_trafo.get_matrix_no_offset());
     }
 
@@ -1496,7 +1495,7 @@ void Selection::scale(const Vec3d& scale, TransformationType transformation_type
 }
 
 #if ENABLE_ENHANCED_PRINT_VOLUME_FIT
-void Selection::scale_to_fit_print_volume(const BuildVolume& volume)
+void Selection::scale_to_fit_print_volume(const BuildVolume& volume, const Vec2d& bed_center, const BoundingBoxf3& print_volume)
 {
     auto fit = [this](double s, Vec3d offset) {
         if (s <= 0.0 || s == 1.0)
@@ -1526,8 +1525,7 @@ void Selection::scale_to_fit_print_volume(const BuildVolume& volume)
         //wxGetApp().obj_manipul()->set_dirty();
     };
 
-    auto fit_rectangle = [this, fit](const BuildVolume& volume) {
-        const BoundingBoxf3 print_volume = volume.bounding_volume();
+    auto fit_rectangle = [this, fit, &print_volume]() {
         const Vec3d print_volume_size = print_volume.size();
 
         // adds 1/100th of a mm on all sides to avoid false out of print volume detections due to floating-point roundings
@@ -1541,7 +1539,7 @@ void Selection::scale_to_fit_print_volume(const BuildVolume& volume)
             fit(std::min(sx, std::min(sy, sz)), print_volume.center() - get_bounding_box().center());
     };
 
-    auto fit_circle = [this, fit](const BuildVolume& volume) {
+    auto fit_circle = [this, fit, &bed_center](const BuildVolume& volume) {
         const Geometry::Circled& print_circle = volume.circle();
         double print_circle_radius = unscale<double>(print_circle.radius);
 
@@ -1572,7 +1570,9 @@ void Selection::scale_to_fit_print_volume(const BuildVolume& volume)
         const double s = std::min(print_circle_radius / circle_radius, volume.printable_height() / max_z);
         const Vec3d sel_center = get_bounding_box().center();
         const Vec3d offset = s * (Vec3d(unscale<double>(circle.center.x()), unscale<double>(circle.center.y()), 0.5 * max_z) - sel_center);
-        const Vec3d print_center = { unscale<double>(print_circle.center.x()), unscale<double>(print_circle.center.y()), 0.5 * volume.printable_height() };
+        // The active plate's bed is the same circle, moved by its centre.
+        const Vec3d plate_shift = Vec3d(bed_center.x() - volume.bed_center().x(), bed_center.y() - volume.bed_center().y(), 0.);
+        const Vec3d print_center = Vec3d(unscale<double>(print_circle.center.x()), unscale<double>(print_circle.center.y()), 0.5 * volume.printable_height()) + plate_shift;
         fit(s, print_center - (sel_center + offset));
     };
 
@@ -1581,7 +1581,7 @@ void Selection::scale_to_fit_print_volume(const BuildVolume& volume)
 
     switch (volume.type())
     {
-    case BuildVolume_Type::Rectangle: { fit_rectangle(volume); break; }
+    case BuildVolume_Type::Rectangle: { fit_rectangle(); break; }
     case BuildVolume_Type::Circle:    { fit_circle(volume); break; }
     default: { break; }
     }

src/slic3r/GUI/Selection.hpp

@@ -354,7 +354,10 @@ public:
     void flattening_rotate(const Vec3d& normal);
     void scale(const Vec3d& scale, TransformationType transformation_type);
 #if ENABLE_ENHANCED_PRINT_VOLUME_FIT
-    void scale_to_fit_print_volume(const BuildVolume& volume);
+    // bed_center is the centre of the plate the selection is on: every plate shares the
+    // bed size, but each sits at its own origin. print_volume is the box the selection must
+    // fit in, which is the area every nozzle reaches rather than the whole bed.
+    void scale_to_fit_print_volume(const BuildVolume& volume, const Vec2d& bed_center, const BoundingBoxf3& print_volume);
 #else
     void scale_to_fit_print_volume(const DynamicPrintConfig& config);
 #endif // ENABLE_ENHANCED_PRINT_VOLUME_FIT

tests/libslic3r/test_arrange.cpp

@@ -220,11 +220,39 @@ TEST_CASE("An item larger than the bed cannot be placed", "[Arrange]")
     ArrangePolygons items;
     items.emplace_back(make_square(scaled(20.)));
     items.emplace_back(make_square(scaled(400.))); // far bigger than the bed
+    // An item that cannot be placed keeps the position it came in with, so the
+    // caller can leave it where the user had it.
+    items[1].translation = {scaled(10.), scaled(20.)};
 
     arrange(items, bed(200, 200), quiet_params(scaled(1.)));
 
     REQUIRE(items[0].bed_idx == 0);
     REQUIRE(items[1].bed_idx == UNARRANGED);
+    REQUIRE(items[1].translation.x() == scaled(10.));
+    REQUIRE(items[1].translation.y() == scaled(20.));
+}
+
+TEST_CASE("An item filling the printable area is arranged", "[Arrange]")
+{
+    // The arrange bed keeps a margin from the printable area and the item is widened by
+    // its brim. Neither may keep an item that fits the printable area from being placed.
+    DynamicPrintConfig cfg   = bed_config(); // 200 x 200
+    ArrangeParams      p     = quiet_params();
+
+    ArrangePolygons items = squares(1, 197.);
+    items.front().brim_width = 1.;
+    update_arrange_params(p, &cfg, items);
+    update_selected_items_inflation(items, &cfg, p);
+    arrange(items, get_shrink_bedpts(&cfg, p), p);
+    REQUIRE(items.front().bed_idx == 0);
+
+    // Larger than the printable area is still refused.
+    ArrangeParams   p_large = quiet_params();
+    ArrangePolygons large   = squares(1, 201.);
+    update_arrange_params(p_large, &cfg, large);
+    update_selected_items_inflation(large, &cfg, p_large);
+    arrange(large, get_shrink_bedpts(&cfg, p_large), p_large);
+    REQUIRE(large.front().bed_idx == UNARRANGED);
 }
 
 TEST_CASE("Items overflowing one bed spill onto virtual beds", "[Arrange]")

tests/libslic3r/test_lay_on_face.cpp

@@ -187,6 +187,23 @@ TEST_CASE("A part rests on its largest hull face even when parallel inner faces
     check_on_bed(plate);
 }
 
+TEST_CASE("A box laid on its top face is turned over about X", "[LayOnFace]")
+{
+    // A face pointing straight up leaves the half turn's axis open to every horizontal
+    // direction. It must be the fixed X flip both times, keep the footprint and not follow
+    // rounding noise to an arbitrary angle.
+    Model        model;
+    ModelObject &box = add_box_object(model, { 40, 20, 10 });
+    lay_on_face(box, 0, { 0, 0, 1 });
+
+    check_size(box, { 40, 20, 10 });
+    check_on_bed(box);
+    const Matrix3d rotation = box.instances.front()->get_matrix_no_offset().linear();
+    CHECK_THAT(rotation(0, 0), WithinAbs(1., 1e-9));
+    CHECK_THAT(rotation(1, 1), WithinAbs(-1., 1e-9));
+    CHECK_THAT(rotation(2, 2), WithinAbs(-1., 1e-9));
+}
+
 TEST_CASE("Faces are selected in object coordinates whatever the instance rotation", "[LayOnFace]")
 {
     Model        model;