Add an option to segment leveled moves

Marlin/Conditionals_post.h

   /**
    * Set granular options based on the specific type of leveling
    */
-  #define UBL_DELTA  (ENABLED(AUTO_BED_LEVELING_UBL) && (ENABLED(DELTA) || ENABLED(UBL_GRANULAR_SEGMENTATION_FOR_CARTESIAN)))
+  #define UBL_DELTA  (ENABLED(AUTO_BED_LEVELING_UBL) && (ENABLED(DELTA) || ENABLED(SEGMENT_LEVELED_MOVES)))
   #define ABL_PLANAR (ENABLED(AUTO_BED_LEVELING_LINEAR) || ENABLED(AUTO_BED_LEVELING_3POINT))
   #define ABL_GRID   (ENABLED(AUTO_BED_LEVELING_LINEAR) || ENABLED(AUTO_BED_LEVELING_BILINEAR))
   #define OLDSCHOOL_ABL         (ABL_PLANAR || ABL_GRID)
     #define PROBE_BED_HEIGHT abs(BACK_PROBE_BED_POSITION - (FRONT_PROBE_BED_POSITION))
   #endif
 
+  #if ENABLED(SEGMENT_LEVELED_MOVES) && !defined(LEVELED_SEGMENT_LENGTH)
+    #define LEVELED_SEGMENT_LENGTH 5
+  #endif
+
   /**
    * Bed Probing rectangular bounds
    * These can be further constrained in code for Delta and SCARA

Marlin/Configuration.h

   // The height can be set with M420 Z<height>
   #define ENABLE_LEVELING_FADE_HEIGHT
 
+  // For Cartesian machines, instead of dividing moves on mesh boundaries,
+  // split up moves into short segments like a Delta.
+  #define SEGMENT_LEVELED_MOVES
+  #define LEVELED_SEGMENT_LENGTH 5.0 // (mm) Length of all segments (except the last one)
+
   /**
    * Enable the G26 Mesh Validation Pattern tool.
    */

Marlin/Marlin_main.cpp

     current_position[axis] = cartes[axis];
 }
 
-#if ENABLED(MESH_BED_LEVELING)
+#if IS_CARTESIAN
+#if ENABLED(SEGMENT_LEVELED_MOVES)
+
+  /**
+   * Prepare a segmented move on a CARTESIAN setup.
+   *
+   * This calls planner.buffer_line several times, adding
+   * small incremental moves. This allows the planner to
+   * apply more detailed bed leveling to the full move.
+   */
+  inline void segmented_line_to_destination(const float fr_mm_s, const float segment_size=LEVELED_SEGMENT_LENGTH) {
+
+    const float xdiff = destination[X_AXIS] - current_position[X_AXIS],
+                ydiff = destination[Y_AXIS] - current_position[Y_AXIS];
+
+    // If the move is only in Z/E don't split up the move
+    if (!xdiff && !ydiff) {
+      planner.buffer_line_kinematic(destination, fr_mm_s, active_extruder);
+      return;
+    }
+
+    // Remaining cartesian distances
+    const float zdiff = destination[Z_AXIS] - current_position[Z_AXIS],
+                ediff = destination[E_AXIS] - current_position[E_AXIS];
+
+    // Get the linear distance in XYZ
+    // If the move is very short, check the E move distance
+    // No E move either? Game over.
+    float cartesian_mm = SQRT(sq(xdiff) + sq(ydiff) + sq(zdiff));
+    if (UNEAR_ZERO(cartesian_mm)) cartesian_mm = FABS(ediff);
+    if (UNEAR_ZERO(cartesian_mm)) return;
+
+    // The length divided by the segment size
+    // At least one segment is required
+    uint16_t segments = cartesian_mm / segment_size;
+    NOLESS(segments, 1);
+
+    // The approximate length of each segment
+    const float inv_segments = 1.0 / float(segments),
+                segment_distance[XYZE] = {
+                  xdiff * inv_segments,
+                  ydiff * inv_segments,
+                  zdiff * inv_segments,
+                  ediff * inv_segments
+                };
+
+    // SERIAL_ECHOPAIR("mm=", cartesian_mm);
+    // SERIAL_ECHOLNPAIR(" segments=", segments);
+
+    // Drop one segment so the last move is to the exact target.
+    // If there's only 1 segment, loops will be skipped entirely.
+    --segments;
+
+    // Get the raw current position as starting point
+    float raw[XYZE];
+    COPY(raw, current_position);
+
+    // Calculate and execute the segments
+    for (uint16_t s = segments + 1; --s;) {
+      static millis_t next_idle_ms = millis() + 200UL;
+      thermalManager.manage_heater();  // This returns immediately if not really needed.
+      if (ELAPSED(millis(), next_idle_ms)) {
+        next_idle_ms = millis() + 200UL;
+        idle();
+      }
+      LOOP_XYZE(i) raw[i] += segment_distance[i];
+      planner.buffer_line_kinematic(raw, fr_mm_s, active_extruder);
+    }
+
+    // Since segment_distance is only approximate,
+    // the final move must be to the exact destination.
+    planner.buffer_line_kinematic(destination, fr_mm_s, active_extruder);
+  }
+
+#elif ENABLED(MESH_BED_LEVELING)
 
   /**
    * Prepare a mesh-leveled linear move in a Cartesian setup,
     mesh_line_to_destination(fr_mm_s, x_splits, y_splits);
   }
 
-#elif ENABLED(AUTO_BED_LEVELING_BILINEAR) && !IS_KINEMATIC
+#elif ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
   #define CELL_INDEX(A,V) ((V - bilinear_start[A##_AXIS]) * ABL_BG_FACTOR(A##_AXIS))
 
   }
 
 #endif // AUTO_BED_LEVELING_BILINEAR
+#endif // IS_CARTESIAN
 
 #if !UBL_DELTA
 #if IS_KINEMATIC
     // Get the top feedrate of the move in the XY plane
     const float _feedrate_mm_s = MMS_SCALED(feedrate_mm_s);
 
+    const float xdiff = rtarget[X_AXIS] - current_position[X_AXIS],
+                ydiff = rtarget[Y_AXIS] - current_position[Y_AXIS];
+
     // If the move is only in Z/E don't split up the move
-    if (rtarget[X_AXIS] == current_position[X_AXIS] && rtarget[Y_AXIS] == current_position[Y_AXIS]) {
+    if (!xdiff && !ydiff) {
       planner.buffer_line_kinematic(rtarget, _feedrate_mm_s, active_extruder);
       return false;
     }
     // Fail if attempting move outside printable radius
     if (!position_is_reachable(rtarget[X_AXIS], rtarget[Y_AXIS])) return true;
 
-    // Get the cartesian distances moved in XYZE
-    const float difference[XYZE] = {
-      rtarget[X_AXIS] - current_position[X_AXIS],
-      rtarget[Y_AXIS] - current_position[Y_AXIS],
-      rtarget[Z_AXIS] - current_position[Z_AXIS],
-      rtarget[E_AXIS] - current_position[E_AXIS]
-    };
+    // Remaining cartesian distances
+    const float zdiff = rtarget[Z_AXIS] - current_position[Z_AXIS],
+                ediff = rtarget[E_AXIS] - current_position[E_AXIS];
 
     // Get the linear distance in XYZ
-    float cartesian_mm = SQRT(sq(difference[X_AXIS]) + sq(difference[Y_AXIS]) + sq(difference[Z_AXIS]));
-
     // If the move is very short, check the E move distance
-    if (UNEAR_ZERO(cartesian_mm)) cartesian_mm = FABS(difference[E_AXIS]);
-
     // No E move either? Game over.
+    float cartesian_mm = SQRT(sq(xdiff) + sq(ydiff) + sq(zdiff));
+    if (UNEAR_ZERO(cartesian_mm)) cartesian_mm = FABS(ediff);
     if (UNEAR_ZERO(cartesian_mm)) return true;
 
     // Minimum number of seconds to move the given distance
     // The approximate length of each segment
     const float inv_segments = 1.0 / float(segments),
                 segment_distance[XYZE] = {
-                  difference[X_AXIS] * inv_segments,
-                  difference[Y_AXIS] * inv_segments,
-                  difference[Z_AXIS] * inv_segments,
-                  difference[E_AXIS] * inv_segments
+                  xdiff * inv_segments,
+                  ydiff * inv_segments,
+                  zdiff * inv_segments,
+                  ediff * inv_segments
                 };
 
     // SERIAL_ECHOPAIR("mm=", cartesian_mm);
    */
   inline bool prepare_move_to_destination_cartesian() {
     #if HAS_MESH
-      if (planner.leveling_active) {
+      if (planner.leveling_active && planner.leveling_active_at_z(destination[Z_AXIS])) {
         #if ENABLED(AUTO_BED_LEVELING_UBL)
           ubl.line_to_destination_cartesian(MMS_SCALED(feedrate_mm_s), active_extruder);  // UBL's motion routine needs to know about
           return true;                                                                    // all moves, including Z-only moves.
+        #elif ENABLED(SEGMENT_LEVELED_MOVES)
+          segmented_line_to_destination(MMS_SCALED(feedrate_mm_s));
+          return false;
         #else
           /**
            * For MBL and ABL-BILINEAR only segment moves when X or Y are involved.

Marlin/SanityCheck.h

   #error "ENABLE_MESH_EDIT_GFX_OVERLAY is now MESH_EDIT_GFX_OVERLAY. Please update your configuration."
 #elif defined(BABYSTEP_ZPROBE_GFX_REVERSE)
   #error "BABYSTEP_ZPROBE_GFX_REVERSE is now set by OVERLAY_GFX_REVERSE. Please update your configurations."
+#elif defined(UBL_GRANULAR_SEGMENTATION_FOR_CARTESIAN)
+  #error "UBL_GRANULAR_SEGMENTATION_FOR_CARTESIAN is now SEGMENT_LEVELED_MOVES. Please update your configuration."
 #endif
 
 /**