Share One Build Plate Tilt Up-Direction Helper Across the GUI

The bed gravity arrow, volume rendering and the painter/support gizmos each rebuilt
the tilt up-vector from build_plate_tilt_x/y; use one helper that also tolerates
presets without the keys.

src/slic3r/GUI/3DBed.cpp

@@ -746,20 +746,14 @@ void Bed3D::render_custom(GLCanvas3D& canvas, const Transform3d& view_matrix, co
 
 void Bed3D::render_gravity_arrow(const Transform3d& view_matrix, const Transform3d& projection_matrix)
 {
-    const DynamicPrintConfig& cfg = wxGetApp().preset_bundle->printers.get_edited_preset().config;
     // build_plate_tilt_{x,y} are kept in sync with the belt tilt (see TabPrinter), so
     // reading them here covers both belt and non-belt tilted printers.
-    double tilt_x_deg = cfg.opt_float("build_plate_tilt_x");
-    double tilt_y_deg = cfg.opt_float("build_plate_tilt_y");
-    if (tilt_x_deg == 0. && tilt_y_deg == 0.) {
+    const Vec3d up_dir = build_plate_tilt_up_direction();
+    if (up_dir == Vec3d::UnitZ()) {
         m_gravity_arrow.reset();
         return;
     }
-
-    // Gravity direction (matching the slicer's tilt convention)
-    double tilt_x_rad = Geometry::deg2rad(tilt_x_deg);
-    double tilt_y_rad = Geometry::deg2rad(tilt_y_deg);
-    Vec3d gravity_dir = Vec3d(-tan(tilt_y_rad), -tan(tilt_x_rad), -1.0).normalized();
+    const Vec3d gravity_dir = -up_dir;
 
     // Build the arrow model (same dimensions as the axis arrows)
     if (!m_gravity_arrow.is_initialized()) {

src/slic3r/GUI/3DScene.cpp

@@ -1133,17 +1133,7 @@ void GLVolumeCollection::render(GLVolumeCollection::ERenderType       type,
 
     // Compute up direction accounting for build plate tilt. This is frame-invariant
     // (config cannot change mid-render), so compute it once before the volume loop.
-    Vec3f up_direction = Vec3f::UnitZ();
-    {
-        const DynamicPrintConfig& prt_cfg = GUI::wxGetApp().preset_bundle->printers.get_edited_preset().config;
-        double tilt_x_deg = prt_cfg.opt_float("build_plate_tilt_x");
-        double tilt_y_deg = prt_cfg.opt_float("build_plate_tilt_y");
-        if (tilt_x_deg != 0. || tilt_y_deg != 0.) {
-            double tilt_x_rad = Geometry::deg2rad(tilt_x_deg);
-            double tilt_y_rad = Geometry::deg2rad(tilt_y_deg);
-            up_direction = Vec3f(float(tan(tilt_y_rad)), float(tan(tilt_x_rad)), 1.f).normalized();
-        }
-    }
+    const Vec3f up_direction = GUI::build_plate_tilt_up_direction().cast<float>();
 
     for (GLVolumeWithIdAndZ& volume : to_render) {
 #if ENABLE_MODIFIERS_ALWAYS_TRANSPARENT

src/slic3r/GUI/GUI_App.cpp

@@ -71,6 +71,7 @@
 #include <openssl/evp.h>
 
 #include "libslic3r/Utils.hpp"
+#include "libslic3r/Geometry.hpp"
 #include "libslic3r/Model.hpp"
 #include "libslic3r/I18N.hpp"
 #include "libslic3r/PresetBundle.hpp"
@@ -10023,5 +10024,17 @@ bool is_support_filament(int extruder_id, bool strict_check)
     return support_option->get_at(0);
 };
 
+Vec3d build_plate_tilt_up_direction()
+{
+    const DynamicPrintConfig &cfg    = wxGetApp().preset_bundle->printers.get_edited_preset().config;
+    const auto               *opt_x  = cfg.option<ConfigOptionFloat>("build_plate_tilt_x");
+    const auto               *opt_y  = cfg.option<ConfigOptionFloat>("build_plate_tilt_y");
+    const double              tilt_x = opt_x != nullptr ? opt_x->value : 0.;
+    const double              tilt_y = opt_y != nullptr ? opt_y->value : 0.;
+    if (tilt_x == 0. && tilt_y == 0.)
+        return Vec3d::UnitZ();
+    return Vec3d(std::tan(Geometry::deg2rad(tilt_y)), std::tan(Geometry::deg2rad(tilt_x)), 1.).normalized();
+}
+
 } // GUI
 } //Slic3r

src/slic3r/GUI/GUI_App.hpp

@@ -833,6 +833,8 @@ bool is_support_filament(int extruder_id, bool strict_check = true);
 bool is_soluble_filament(int extruder_id);
 // check if the filament for model is in the list
 bool has_filaments(const std::vector<string>& model_filaments);
+// Up direction of the edited printer's tilted build plate (+Z when untilted).
+Vec3d build_plate_tilt_up_direction();
 } // namespace GUI
 } // Slic3r
 

src/slic3r/GUI/Gizmos/GLGizmoFdmSupports.cpp

@@ -548,14 +548,6 @@ int GLGizmoFdmSupports::get_selection_support_threshold_angle()
     return auto_support ? support_threshold_angle : 0;
 }
 
-std::pair<double, double> GLGizmoFdmSupports::get_build_plate_tilt()
-{
-    const DynamicPrintConfig& cfg = wxGetApp().preset_bundle->printers.get_edited_preset().config;
-    double tilt_x = cfg.opt_float("build_plate_tilt_x");
-    double tilt_y = cfg.opt_float("build_plate_tilt_y");
-    return {tilt_x, tilt_y};
-}
-
 void GLGizmoFdmSupports::select_facets_by_angle(float threshold_deg, bool block)
 {
     float threshold = (float(M_PI)/180.f)*threshold_deg;
@@ -564,15 +556,9 @@ void GLGizmoFdmSupports::select_facets_by_angle(float threshold_deg, bool block)
     const ModelInstance* mi = mo->instances[selection.get_instance_idx()];
 
     // Compute gravity direction accounting for build plate tilt
-    auto [tilt_x_deg, tilt_y_deg] = get_build_plate_tilt();
-    double tilt_x_rad = tilt_x_deg * M_PI / 180.0;
-    double tilt_y_rad = tilt_y_deg * M_PI / 180.0;
-    const bool has_tilt = (tilt_x_deg != 0. || tilt_y_deg != 0.);
-    // NB: use an if, not a ?:, so each branch converts to Vec3d independently
-    // (the two Eigen expression types don't unify in a ternary).
-    Vec3d gravity_dir = -Vec3d::UnitZ();
-    if (has_tilt)
-        gravity_dir = Vec3d(-tan(tilt_y_rad), -tan(tilt_x_rad), -1.0).normalized();
+    const Vec3d up_dir      = build_plate_tilt_up_direction();
+    const bool  has_tilt    = up_dir != Vec3d::UnitZ();
+    const Vec3d gravity_dir = -up_dir;
 
     int mesh_id = -1;
     for (const ModelVolume* mv : mo->volumes) {

src/slic3r/GUI/Gizmos/GLGizmoFdmSupports.hpp

@@ -60,7 +60,6 @@ private:
     void select_facets_by_angle(float threshold, bool block);
     // BBS
     int get_selection_support_threshold_angle();
-    std::pair<double, double> get_build_plate_tilt();
 
     int m_support_threshold_angle = -1;
 

src/slic3r/GUI/Gizmos/GLGizmoPainterBase.cpp

@@ -75,14 +75,7 @@ GLGizmoPainterBase::ClippingPlaneDataWrapper GLGizmoPainterBase::get_clipping_pl
 
 Vec3f GLGizmoPainterBase::get_tilt_up_direction() const
 {
-    const DynamicPrintConfig& cfg = wxGetApp().preset_bundle->printers.get_edited_preset().config;
-    double tilt_x_deg = cfg.opt_float("build_plate_tilt_x");
-    double tilt_y_deg = cfg.opt_float("build_plate_tilt_y");
-    if (tilt_x_deg == 0. && tilt_y_deg == 0.)
-        return Vec3f::UnitZ();
-    double tilt_x_rad = Geometry::deg2rad(tilt_x_deg);
-    double tilt_y_rad = Geometry::deg2rad(tilt_y_deg);
-    return Vec3f(float(tan(tilt_y_rad)), float(tan(tilt_x_rad)), 1.f).normalized();
+    return build_plate_tilt_up_direction().cast<float>();
 }
 
 void GLGizmoPainterBase::render_triangles(const Selection& selection) const