Move fade_scaling_factor_for_z to Planner

Marlin/src/feature/bedlevel/bedlevel.cpp

     const bool level_active = LEVELING_IS_ACTIVE();
 
     #if ENABLED(AUTO_BED_LEVELING_UBL)
+      if (level_active) set_bed_leveling_enabled(false);  // turn off before changing fade height for proper apply/unapply leveling to maintain current_position
+    #endif
 
-      if (level_active)
-        set_bed_leveling_enabled(false);  // turn off before changing fade height for proper apply/unapply leveling to maintain current_position
-      planner.z_fade_height = zfh;
-      planner.inverse_z_fade_height = RECIPROCAL(zfh);
-      if (level_active)
-        set_bed_leveling_enabled(true);  // turn back on after changing fade height
-
-    #else
-
-      planner.z_fade_height = zfh;
-      planner.inverse_z_fade_height = RECIPROCAL(zfh);
+    planner.z_fade_height = zfh;
+    planner.inverse_z_fade_height = RECIPROCAL(zfh);
 
-      if (level_active) {
+    if (level_active) {
+      #if ENABLED(AUTO_BED_LEVELING_UBL)
+        set_bed_leveling_enabled(true);  // turn back on after changing fade height
+      #else
         set_current_from_steppers_for_axis(
           #if ABL_PLANAR
             ALL_AXES
             Z_AXIS
           #endif
         );
-      }
-    #endif
+      #endif
+    }
   }
 
 #endif // ENABLE_LEVELING_FADE_HEIGHT

Marlin/src/feature/bedlevel/ubl/ubl.h

       return z0;
     }
 
-    /**
-     * This function sets the Z leveling fade factor based on the given Z height,
-     * only re-calculating when necessary.
-     *
-     *  Returns 1.0 if planner.z_fade_height is 0.0.
-     *  Returns 0.0 if Z is past the specified 'Fade Height'.
-     */
-    #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
-      static inline float fade_scaling_factor_for_z(const float &lz) {
-        if (planner.z_fade_height == 0.0) return 1.0;
-        static float fade_scaling_factor = 1.0;
-        const float rz = RAW_Z_POSITION(lz);
-        if (last_specified_z != rz) {
-          last_specified_z = rz;
-          fade_scaling_factor =
-            rz < planner.z_fade_height
-              ? 1.0 - (rz * planner.inverse_z_fade_height)
-              : 0.0;
-        }
-        return fade_scaling_factor;
-      }
-    #else
-      FORCE_INLINE static float fade_scaling_factor_for_z(const float &lz) { return 1.0; }
-    #endif
-
     FORCE_INLINE static float mesh_index_to_xpos(const uint8_t i) {
       return i < GRID_MAX_POINTS_X ? pgm_read_float(&_mesh_index_to_xpos[i]) : UBL_MESH_MIN_X + i * (MESH_X_DIST);
     }

Marlin/src/feature/bedlevel/ubl/ubl_motion.cpp

       // are going to apply the Y-Distance into the cell to interpolate the final Z correction.
 
       const float yratio = (RAW_Y_POSITION(end[Y_AXIS]) - mesh_index_to_ypos(cell_dest_yi)) * (1.0 / (MESH_Y_DIST));
-      float z0 = cell_dest_yi < GRID_MAX_POINTS_Y - 1 ? (z1 + (z2 - z1) * yratio) * fade_scaling_factor_for_z(end[Z_AXIS]) : 0.0;
+      float z0 = cell_dest_yi < GRID_MAX_POINTS_Y - 1 ? (z1 + (z2 - z1) * yratio) * planner.fade_scaling_factor_for_z(end[Z_AXIS]) : 0.0;
 
       /**
        * If part of the Mesh is undefined, it will show up as NAN
 
         float z0 = z_correction_for_x_on_horizontal_mesh_line(x, current_xi, current_yi);
 
-        z0 *= fade_scaling_factor_for_z(end[Z_AXIS]);
+        z0 *= planner.fade_scaling_factor_for_z(end[Z_AXIS]);
 
         /**
          * If part of the Mesh is undefined, it will show up as NAN
 
         float z0 = z_correction_for_y_on_vertical_mesh_line(y, current_xi, current_yi);
 
-        z0 *= fade_scaling_factor_for_z(end[Z_AXIS]);
+        z0 *= planner.fade_scaling_factor_for_z(end[Z_AXIS]);
 
         /**
          * If part of the Mesh is undefined, it will show up as NAN
         // Yes!  Crossing a Y Mesh Line next
         float z0 = z_correction_for_x_on_horizontal_mesh_line(x, current_xi - left_flag, current_yi + dyi);
 
-        z0 *= fade_scaling_factor_for_z(end[Z_AXIS]);
+        z0 *= planner.fade_scaling_factor_for_z(end[Z_AXIS]);
 
         /**
          * If part of the Mesh is undefined, it will show up as NAN
         // Yes!  Crossing a X Mesh Line next
         float z0 = z_correction_for_y_on_vertical_mesh_line(y, current_xi + dxi, current_yi - down_flag);
 
-        z0 *= fade_scaling_factor_for_z(end[Z_AXIS]);
+        z0 *= planner.fade_scaling_factor_for_z(end[Z_AXIS]);
 
         /**
          * If part of the Mesh is undefined, it will show up as NAN
       // Otherwise perform per-segment leveling
 
       #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
-        const float fade_scaling_factor = fade_scaling_factor_for_z(ltarget[Z_AXIS]);
+        const float fade_scaling_factor = planner.fade_scaling_factor_for_z(ltarget[Z_AXIS]);
       #endif
 
       // increment to first segment destination

Marlin/src/module/planner.cpp

 
 #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
   float Planner::z_fade_height, // Initialized by settings.load()
-        Planner::inverse_z_fade_height;
+        Planner::inverse_z_fade_height,
+        Planner::last_raw_lz;
 #endif
 
 #if ENABLED(AUTOTEMP)
 
     if (!LEVELING_IS_ACTIVE()) return;
 
-    #if ENABLED(AUTO_BED_LEVELING_UBL)
-      #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
-        // if z_fade_height enabled (nonzero) and raw_z above it, no leveling required
-        if (planner.z_fade_height && planner.z_fade_height <= RAW_Z_POSITION(lz)) return;
-        lz += ubl.get_z_correction(lx, ly) * ubl.fade_scaling_factor_for_z(lz);
-      #else // no fade
-        lz += ubl.get_z_correction(lx, ly);
-      #endif // FADE
-    #endif // UBL
-
-    #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT) && DISABLED(AUTO_BED_LEVELING_UBL)
-      static float z_fade_factor = 1.0, last_raw_lz = -999.0;
-      if (z_fade_height) {
-        const float raw_lz = RAW_Z_POSITION(lz);
-        if (raw_lz >= z_fade_height) return;
-        if (last_raw_lz != raw_lz) {
-          last_raw_lz = raw_lz;
-          z_fade_factor = 1.0 - raw_lz * inverse_z_fade_height;
-        }
-      }
-      else
-        z_fade_factor = 1.0;
+    #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
+      const float fade_scaling_factor = fade_scaling_factor_for_z(lz);
+      if (!fade_scaling_factor) return;
+    #else
+      constexpr float fade_scaling_factor = 1.0;
     #endif
 
-    #if ENABLED(MESH_BED_LEVELING)
+    #if ENABLED(AUTO_BED_LEVELING_UBL)
+
+      lz += ubl.get_z_correction(lx, ly) * fade_scaling_factor;
+
+    #elif ENABLED(MESH_BED_LEVELING)
 
       lz += mbl.get_z(RAW_X_POSITION(lx), RAW_Y_POSITION(ly)
         #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
-          , z_fade_factor
+          , fade_scaling_factor
         #endif
-        );
+      );
 
     #elif ABL_PLANAR
 
+      UNUSED(fade_scaling_factor);
+
       float dx = RAW_X_POSITION(lx) - (X_TILT_FULCRUM),
             dy = RAW_Y_POSITION(ly) - (Y_TILT_FULCRUM),
             dz = RAW_Z_POSITION(lz);
     #elif ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
       float tmp[XYZ] = { lx, ly, 0 };
-      lz += bilinear_z_offset(tmp)
-        #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
-          * z_fade_factor
-        #endif
-      ;
+      lz += bilinear_z_offset(tmp) * fade_scaling_factor;
 
     #endif
   }

Marlin/src/module/planner.h

         if (!filament_size[i]) filament_size[i] = DEFAULT_NOMINAL_FILAMENT_DIA;
     }
 
+    #if ENABLED(ENABLE_LEVELING_FADE_HEIGHT)
+
+      /**
+       * Get the Z leveling fade factor based on the given Z height,
+       * re-calculating only when needed.
+       *
+       *  Returns 1.0 if planner.z_fade_height is 0.0.
+       *  Returns 0.0 if Z is past the specified 'Fade Height'.
+       */
+      inline static float fade_scaling_factor_for_z(const float &lz) {
+        static float z_fade_factor = 1.0, last_raw_lz = -999.0;
+        if (z_fade_height) {
+          const float raw_lz = RAW_Z_POSITION(lz);
+          if (raw_lz >= z_fade_height) return 0.0;
+          if (last_raw_lz != raw_lz) {
+            last_raw_lz = raw_lz;
+            z_fade_factor = 1.0 - raw_lz * inverse_z_fade_height;
+          }
+          return z_fade_factor;
+        }
+        return 1.0;
+      }
+
+    #else
+
+      FORCE_INLINE static float fade_scaling_factor_for_z(const float &lz) {
+        UNUSED(lz);
+        return 1.0;
+      }
+
+    #endif
+
     #if PLANNER_LEVELING
 
       #define ARG_X float lx