Example #1
0
    void unified_bed_leveling::line_to_destination_cartesian(const float &feed_rate, const uint8_t extruder) {
      /**
       * Much of the nozzle movement will be within the same cell. So we will do as little computation
       * as possible to determine if this is the case. If this move is within the same cell, we will
       * just do the required Z-Height correction, call the Planner's buffer_line() routine, and leave
       */
      #if ENABLED(SKEW_CORRECTION)
        // For skew correction just adjust the destination point and we're done
        float start[XYZE] = { current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS] },
              end[XYZE] = { destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS] };
        planner.skew(start[X_AXIS], start[Y_AXIS], start[Z_AXIS]);
        planner.skew(end[X_AXIS], end[Y_AXIS], end[Z_AXIS]);
      #else
        const float (&start)[XYZE] = current_position,
                      (&end)[XYZE] = destination;
      #endif

      const int cell_start_xi = get_cell_index_x(start[X_AXIS]),
                cell_start_yi = get_cell_index_y(start[Y_AXIS]),
                cell_dest_xi  = get_cell_index_x(end[X_AXIS]),
                cell_dest_yi  = get_cell_index_y(end[Y_AXIS]);

      if (g26_debug_flag) {
        SERIAL_ECHOPAIR(" ubl.line_to_destination_cartesian(xe=", destination[X_AXIS]);
        SERIAL_ECHOPAIR(", ye=", destination[Y_AXIS]);
        SERIAL_ECHOPAIR(", ze=", destination[Z_AXIS]);
        SERIAL_ECHOPAIR(", ee=", destination[E_AXIS]);
        SERIAL_CHAR(')');
        SERIAL_EOL();
        debug_current_and_destination(PSTR("Start of ubl.line_to_destination_cartesian()"));
      }

      // A move within the same cell needs no splitting
      if (cell_start_xi == cell_dest_xi && cell_start_yi == cell_dest_yi) {

        // For a move off the bed, use a constant Z raise
        if (!WITHIN(cell_dest_xi, 0, GRID_MAX_POINTS_X - 1) || !WITHIN(cell_dest_yi, 0, GRID_MAX_POINTS_Y - 1)) {

          // Note: There is no Z Correction in this case. We are off the grid and don't know what
          // a reasonable correction would be.  If the user has specified a UBL_Z_RAISE_WHEN_OFF_MESH
          // value, that will be used instead of a calculated (Bi-Linear interpolation) correction.

          const float z_raise = 0.0
            #ifdef UBL_Z_RAISE_WHEN_OFF_MESH
              + UBL_Z_RAISE_WHEN_OFF_MESH
            #endif
          ;
          planner.buffer_segment(end[X_AXIS], end[Y_AXIS], end[Z_AXIS] + z_raise, end[E_AXIS], feed_rate, extruder);
          set_current_from_destination();

          if (g26_debug_flag)
            debug_current_and_destination(PSTR("out of bounds in ubl.line_to_destination_cartesian()"));

          return;
        }

        FINAL_MOVE:

        // The distance is always MESH_X_DIST so multiply by the constant reciprocal.
        const float xratio = (end[X_AXIS] - mesh_index_to_xpos(cell_dest_xi)) * (1.0f / (MESH_X_DIST));

        float z1 = z_values[cell_dest_xi    ][cell_dest_yi    ] + xratio *
                  (z_values[cell_dest_xi + 1][cell_dest_yi    ] - z_values[cell_dest_xi][cell_dest_yi    ]),
              z2 = z_values[cell_dest_xi    ][cell_dest_yi + 1] + xratio *
                  (z_values[cell_dest_xi + 1][cell_dest_yi + 1] - z_values[cell_dest_xi][cell_dest_yi + 1]);

        if (cell_dest_xi >= GRID_MAX_POINTS_X - 1) z1 = z2 = 0.0;

        // X cell-fraction done. Interpolate the two Z offsets with the Y fraction for the final Z offset.
        const float yratio = (end[Y_AXIS] - mesh_index_to_ypos(cell_dest_yi)) * (1.0f / (MESH_Y_DIST)),
                    z0 = cell_dest_yi < GRID_MAX_POINTS_Y - 1 ? (z1 + (z2 - z1) * yratio) * planner.fade_scaling_factor_for_z(end[Z_AXIS]) : 0.0;

        // Undefined parts of the Mesh in z_values[][] are NAN.
        // Replace NAN corrections with 0.0 to prevent NAN propagation.
        planner.buffer_segment(end[X_AXIS], end[Y_AXIS], end[Z_AXIS] + (isnan(z0) ? 0.0 : z0), end[E_AXIS], feed_rate, extruder);

        if (g26_debug_flag)
          debug_current_and_destination(PSTR("FINAL_MOVE in ubl.line_to_destination_cartesian()"));

        set_current_from_destination();
        return;
      }

      /**
       * Past this point the move is known to cross one or more mesh lines. Check for the most common
       * case - crossing only one X or Y line - after details are worked out to reduce computation.
       */

      const float dx = end[X_AXIS] - start[X_AXIS],
                  dy = end[Y_AXIS] - start[Y_AXIS];

      const int left_flag = dx < 0.0 ? 1 : 0,
                down_flag = dy < 0.0 ? 1 : 0;

      const float adx = left_flag ? -dx : dx,
                  ady = down_flag ? -dy : dy;

      const int dxi = cell_start_xi == cell_dest_xi ? 0 : left_flag ? -1 : 1,
                dyi = cell_start_yi == cell_dest_yi ? 0 : down_flag ? -1 : 1;

      /**
       * Compute the extruder scaling factor for each partial move, checking for
       * zero-length moves that would result in an infinite scaling factor.
       * A float divide is required for this, but then it just multiplies.
       * Also select a scaling factor based on the larger of the X and Y
       * components. The larger of the two is used to preserve precision.
       */

      const bool use_x_dist = adx > ady;

      float on_axis_distance = use_x_dist ? dx : dy,
            e_position = end[E_AXIS] - start[E_AXIS],
            z_position = end[Z_AXIS] - start[Z_AXIS];

      const float e_normalized_dist = e_position / on_axis_distance,
                  z_normalized_dist = z_position / on_axis_distance;

      int current_xi = cell_start_xi,
          current_yi = cell_start_yi;

      const float m = dy / dx,
                  c = start[Y_AXIS] - m * start[X_AXIS];

      const bool inf_normalized_flag = (isinf(e_normalized_dist) != 0),
                 inf_m_flag = (isinf(m) != 0);

      /**
       * Handle vertical lines that stay within one column.
       * These need not be perfectly vertical.
       */
      if (dxi == 0) {             // Vertical line?
        current_yi += down_flag;  // Line going down? Just go to the bottom.
        while (current_yi != cell_dest_yi + down_flag) {
          current_yi += dyi;
          const float next_mesh_line_y = mesh_index_to_ypos(current_yi);

          /**
           * Skip the calculations for an infinite slope.
           * For others the next X is the same so this can continue.
           * Calculate X at the next Y mesh line.
           */
          const float rx = inf_m_flag ? start[X_AXIS] : (next_mesh_line_y - c) / m;

          float z0 = z_correction_for_x_on_horizontal_mesh_line(rx, current_xi, current_yi)
                     * planner.fade_scaling_factor_for_z(end[Z_AXIS]);

          // Undefined parts of the Mesh in z_values[][] are NAN.
          // Replace NAN corrections with 0.0 to prevent NAN propagation.
          if (isnan(z0)) z0 = 0.0;

          const float ry = mesh_index_to_ypos(current_yi);

          /**
           * Without this check, it's possible to generate a zero length move, as in the case where
           * the line is heading down, starting exactly on a mesh line boundary. Since this is rare
           * it might be fine to remove this check and let planner.buffer_segment() filter it out.
           */
          if (ry != start[Y_AXIS]) {
            if (!inf_normalized_flag) {
              on_axis_distance = use_x_dist ? rx - start[X_AXIS] : ry - start[Y_AXIS];
              e_position = start[E_AXIS] + on_axis_distance * e_normalized_dist;
              z_position = start[Z_AXIS] + on_axis_distance * z_normalized_dist;
            }
            else {
              e_position = end[E_AXIS];
              z_position = end[Z_AXIS];
            }

            planner.buffer_segment(rx, ry, z_position + z0, e_position, feed_rate, extruder);
          } //else printf("FIRST MOVE PRUNED  ");
        }

        if (g26_debug_flag)
          debug_current_and_destination(PSTR("vertical move done in ubl.line_to_destination_cartesian()"));

        // At the final destination? Usually not, but when on a Y Mesh Line it's completed.
        if (current_position[X_AXIS] != end[X_AXIS] || current_position[Y_AXIS] != end[Y_AXIS])
          goto FINAL_MOVE;

        set_current_from_destination();
        return;
      }

      /**
       * Handle horizontal lines that stay within one row.
       * These need not be perfectly horizontal.
       */
      if (dyi == 0) {             // Horizontal line?
        current_xi += left_flag;  // Heading left? Just go to the left edge of the cell for the first move.
        while (current_xi != cell_dest_xi + left_flag) {
          current_xi += dxi;
          const float next_mesh_line_x = mesh_index_to_xpos(current_xi),
                      ry = m * next_mesh_line_x + c;   // Calculate Y at the next X mesh line

          float z0 = z_correction_for_y_on_vertical_mesh_line(ry, current_xi, current_yi)
                     * planner.fade_scaling_factor_for_z(end[Z_AXIS]);

          // Undefined parts of the Mesh in z_values[][] are NAN.
          // Replace NAN corrections with 0.0 to prevent NAN propagation.
          if (isnan(z0)) z0 = 0.0;

          const float rx = mesh_index_to_xpos(current_xi);

          /**
           * Without this check, it's possible to generate a zero length move, as in the case where
           * the line is heading left, starting exactly on a mesh line boundary. Since this is rare
           * it might be fine to remove this check and let planner.buffer_segment() filter it out.
           */
          if (rx != start[X_AXIS]) {
            if (!inf_normalized_flag) {
              on_axis_distance = use_x_dist ? rx - start[X_AXIS] : ry - start[Y_AXIS];
              e_position = start[E_AXIS] + on_axis_distance * e_normalized_dist;  // is based on X or Y because this is a horizontal move
              z_position = start[Z_AXIS] + on_axis_distance * z_normalized_dist;
            }
            else {
              e_position = end[E_AXIS];
              z_position = end[Z_AXIS];
            }

            if (!planner.buffer_segment(rx, ry, z_position + z0, e_position, feed_rate, extruder))
              break;
          } //else printf("FIRST MOVE PRUNED  ");
        }

        if (g26_debug_flag)
          debug_current_and_destination(PSTR("horizontal move done in ubl.line_to_destination_cartesian()"));

        if (current_position[X_AXIS] != end[X_AXIS] || current_position[Y_AXIS] != end[Y_AXIS])
          goto FINAL_MOVE;

        set_current_from_destination();
        return;
      }

      /**
       *
       * Handle the generic case of a line crossing both X and Y Mesh lines.
       *
       */

      int xi_cnt = cell_start_xi - cell_dest_xi,
          yi_cnt = cell_start_yi - cell_dest_yi;

      if (xi_cnt < 0) xi_cnt = -xi_cnt;
      if (yi_cnt < 0) yi_cnt = -yi_cnt;

      current_xi += left_flag;
      current_yi += down_flag;

      while (xi_cnt || yi_cnt) {

        const float next_mesh_line_x = mesh_index_to_xpos(current_xi + dxi),
                    next_mesh_line_y = mesh_index_to_ypos(current_yi + dyi),
                    ry = m * next_mesh_line_x + c,   // Calculate Y at the next X mesh line
                    rx = (next_mesh_line_y - c) / m; // Calculate X at the next Y mesh line
                                                     // (No need to worry about m being zero.
                                                     //  If that was the case, it was already detected
                                                     //  as a vertical line move above.)

        if (left_flag == (rx > next_mesh_line_x)) { // Check if we hit the Y line first
          // Yes!  Crossing a Y Mesh Line next
          float z0 = z_correction_for_x_on_horizontal_mesh_line(rx, current_xi - left_flag, current_yi + dyi)
                     * planner.fade_scaling_factor_for_z(end[Z_AXIS]);

          // Undefined parts of the Mesh in z_values[][] are NAN.
          // Replace NAN corrections with 0.0 to prevent NAN propagation.
          if (isnan(z0)) z0 = 0.0;

          if (!inf_normalized_flag) {
            on_axis_distance = use_x_dist ? rx - start[X_AXIS] : next_mesh_line_y - start[Y_AXIS];
            e_position = start[E_AXIS] + on_axis_distance * e_normalized_dist;
            z_position = start[Z_AXIS] + on_axis_distance * z_normalized_dist;
          }
          else {
            e_position = end[E_AXIS];
            z_position = end[Z_AXIS];
          }
          if (!planner.buffer_segment(rx, next_mesh_line_y, z_position + z0, e_position, feed_rate, extruder))
            break;
          current_yi += dyi;
          yi_cnt--;
        }
        else {
          // Yes!  Crossing a X Mesh Line next
          float z0 = z_correction_for_y_on_vertical_mesh_line(ry, current_xi + dxi, current_yi - down_flag)
                     * planner.fade_scaling_factor_for_z(end[Z_AXIS]);

          // Undefined parts of the Mesh in z_values[][] are NAN.
          // Replace NAN corrections with 0.0 to prevent NAN propagation.
          if (isnan(z0)) z0 = 0.0;

          if (!inf_normalized_flag) {
            on_axis_distance = use_x_dist ? next_mesh_line_x - start[X_AXIS] : ry - start[Y_AXIS];
            e_position = start[E_AXIS] + on_axis_distance * e_normalized_dist;
            z_position = start[Z_AXIS] + on_axis_distance * z_normalized_dist;
          }
          else {
            e_position = end[E_AXIS];
            z_position = end[Z_AXIS];
          }

          if (!planner.buffer_segment(next_mesh_line_x, ry, z_position + z0, e_position, feed_rate, extruder))
            break;
          current_xi += dxi;
          xi_cnt--;
        }

        if (xi_cnt < 0 || yi_cnt < 0) break; // Too far! Exit the loop and go to FINAL_MOVE
      }

      if (g26_debug_flag)
        debug_current_and_destination(PSTR("generic move done in ubl.line_to_destination_cartesian()"));

      if (current_position[X_AXIS] != end[X_AXIS] || current_position[Y_AXIS] != end[Y_AXIS])
        goto FINAL_MOVE;

      set_current_from_destination();
    }
Example #2
0
    void unified_bed_leveling::line_to_destination_cartesian(const float &feed_rate, const uint8_t extruder) {
      /**
       * Much of the nozzle movement will be within the same cell. So we will do as little computation
       * as possible to determine if this is the case. If this move is within the same cell, we will
       * just do the required Z-Height correction, call the Planner's buffer_line() routine, and leave
       */
      #if ENABLED(SKEW_CORRECTION)
        // For skew correction just adjust the destination point and we're done
        float start[XYZE] = { current_position[X_AXIS], current_position[Y_AXIS], current_position[Z_AXIS], current_position[E_AXIS] },
              end[XYZE] = { destination[X_AXIS], destination[Y_AXIS], destination[Z_AXIS], destination[E_AXIS] };
        planner.skew(start[X_AXIS], start[Y_AXIS], start[Z_AXIS]);
        planner.skew(end[X_AXIS], end[Y_AXIS], end[Z_AXIS]);
      #else
        const float (&start)[XYZE] = current_position,
                      (&end)[XYZE] = destination;
      #endif

      const int cell_start_xi = get_cell_index_x(start[X_AXIS]),
                cell_start_yi = get_cell_index_y(start[Y_AXIS]),
                cell_dest_xi  = get_cell_index_x(end[X_AXIS]),
                cell_dest_yi  = get_cell_index_y(end[Y_AXIS]);

      if (g26_debug_flag) {
        SERIAL_ECHOPAIR(" ubl.line_to_destination_cartesian(xe=", destination[X_AXIS]);
        SERIAL_ECHOPAIR(", ye=", destination[Y_AXIS]);
        SERIAL_ECHOPAIR(", ze=", destination[Z_AXIS]);
        SERIAL_ECHOPAIR(", ee=", destination[E_AXIS]);
        SERIAL_CHAR(')');
        SERIAL_EOL();
        debug_current_and_destination(PSTR("Start of ubl.line_to_destination_cartesian()"));
      }

      if (cell_start_xi == cell_dest_xi && cell_start_yi == cell_dest_yi) { // if the whole move is within the same cell,
        /**
         * we don't need to break up the move
         *
         * If we are moving off the print bed, we are going to allow the move at this level.
         * But we detect it and isolate it. For now, we just pass along the request.
         */

        if (!WITHIN(cell_dest_xi, 0, GRID_MAX_POINTS_X - 1) || !WITHIN(cell_dest_yi, 0, GRID_MAX_POINTS_Y - 1)) {

          // Note: There is no Z Correction in this case. We are off the grid and don't know what
          // a reasonable correction would be.

          planner.buffer_segment(end[X_AXIS], end[Y_AXIS], end[Z_AXIS], end[E_AXIS], feed_rate, extruder);
          set_current_from_destination();

          if (g26_debug_flag)
            debug_current_and_destination(PSTR("out of bounds in ubl.line_to_destination_cartesian()"));

          return;
        }

        FINAL_MOVE:

        /**
         * Optimize some floating point operations here. We could call float get_z_correction(float x0, float y0) to
         * generate the correction for us. But we can lighten the load on the CPU by doing a modified version of the function.
         * We are going to only calculate the amount we are from the first mesh line towards the second mesh line once.
         * We will use this fraction in both of the original two Z Height calculations for the bi-linear interpolation. And,
         * instead of doing a generic divide of the distance, we know the distance is MESH_X_DIST so we can use the preprocessor
         * to create a 1-over number for us. That will allow us to do a floating point multiply instead of a floating point divide.
         */

        const float xratio = (end[X_AXIS] - mesh_index_to_xpos(cell_dest_xi)) * (1.0 / (MESH_X_DIST));

        float z1 = z_values[cell_dest_xi    ][cell_dest_yi    ] + xratio *
                  (z_values[cell_dest_xi + 1][cell_dest_yi    ] - z_values[cell_dest_xi][cell_dest_yi    ]),
              z2 = z_values[cell_dest_xi    ][cell_dest_yi + 1] + xratio *
                  (z_values[cell_dest_xi + 1][cell_dest_yi + 1] - z_values[cell_dest_xi][cell_dest_yi + 1]);

        if (cell_dest_xi >= GRID_MAX_POINTS_X - 1) z1 = z2 = 0.0;

        // we are done with the fractional X distance into the cell. Now with the two Z-Heights we have calculated, we
        // are going to apply the Y-Distance into the cell to interpolate the final Z correction.

        const float yratio = (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) * planner.fade_scaling_factor_for_z(end[Z_AXIS]) : 0.0;

        /**
         * If part of the Mesh is undefined, it will show up as NAN
         * in z_values[][] and propagate through the
         * calculations. If our correction is NAN, we throw it out
         * because part of the Mesh is undefined and we don't have the
         * information we need to complete the height correction.
         */
        if (isnan(z0)) z0 = 0.0;

        planner.buffer_segment(end[X_AXIS], end[Y_AXIS], end[Z_AXIS] + z0, end[E_AXIS], feed_rate, extruder);

        if (g26_debug_flag)
          debug_current_and_destination(PSTR("FINAL_MOVE in ubl.line_to_destination_cartesian()"));

        set_current_from_destination();
        return;
      }

      /**
       * If we get here, we are processing a move that crosses at least one Mesh Line. We will check
       * for the simple case of just crossing X or just crossing Y Mesh Lines after we get all the details
       * of the move figured out. We can process the easy case of just crossing an X or Y Mesh Line with less
       * computation and in fact most lines are of this nature. We will check for that in the following
       * blocks of code:
       */

      const float dx = end[X_AXIS] - start[X_AXIS],
                  dy = end[Y_AXIS] - start[Y_AXIS];

      const int left_flag = dx < 0.0 ? 1 : 0,
                down_flag = dy < 0.0 ? 1 : 0;

      const float adx = left_flag ? -dx : dx,
                  ady = down_flag ? -dy : dy;

      const int dxi = cell_start_xi == cell_dest_xi ? 0 : left_flag ? -1 : 1,
                dyi = cell_start_yi == cell_dest_yi ? 0 : down_flag ? -1 : 1;

      /**
       * Compute the scaling factor for the extruder for each partial move.
       * We need to watch out for zero length moves because it will cause us to
       * have an infinate scaling factor. We are stuck doing a floating point
       * divide to get our scaling factor, but after that, we just multiply by this
       * number. We also pick our scaling factor based on whether the X or Y
       * component is larger. We use the biggest of the two to preserve precision.
       */

      const bool use_x_dist = adx > ady;

      float on_axis_distance = use_x_dist ? dx : dy,
            e_position = end[E_AXIS] - start[E_AXIS],
            z_position = end[Z_AXIS] - start[Z_AXIS];

      const float e_normalized_dist = e_position / on_axis_distance,
                  z_normalized_dist = z_position / on_axis_distance;

      int current_xi = cell_start_xi,
          current_yi = cell_start_yi;

      const float m = dy / dx,
                  c = start[Y_AXIS] - m * start[X_AXIS];

      const bool inf_normalized_flag = (isinf(e_normalized_dist) != 0),
                 inf_m_flag = (isinf(m) != 0);
      /**
       * This block handles vertical lines. These are lines that stay within the same
       * X Cell column. They do not need to be perfectly vertical. They just can
       * not cross into another X Cell column.
       */
      if (dxi == 0) {       // Check for a vertical line
        current_yi += down_flag;  // Line is heading down, we just want to go to the bottom
        while (current_yi != cell_dest_yi + down_flag) {
          current_yi += dyi;
          const float next_mesh_line_y = mesh_index_to_ypos(current_yi);

          /**
           * if the slope of the line is infinite, we won't do the calculations
           * else, we know the next X is the same so we can recover and continue!
           * Calculate X at the next Y mesh line
           */
          const float rx = inf_m_flag ? start[X_AXIS] : (next_mesh_line_y - c) / m;

          float z0 = z_correction_for_x_on_horizontal_mesh_line(rx, current_xi, current_yi)
                     * planner.fade_scaling_factor_for_z(end[Z_AXIS]);

          /**
           * If part of the Mesh is undefined, it will show up as NAN
           * in z_values[][] and propagate through the
           * calculations. If our correction is NAN, we throw it out
           * because part of the Mesh is undefined and we don't have the
           * information we need to complete the height correction.
           */
          if (isnan(z0)) z0 = 0.0;

          const float ry = mesh_index_to_ypos(current_yi);

          /**
           * Without this check, it is possible for the algorithm to generate a zero length move in the case
           * where the line is heading down and it is starting right on a Mesh Line boundary. For how often that
           * happens, it might be best to remove the check and always 'schedule' the move because
           * the planner.buffer_segment() routine will filter it if that happens.
           */
          if (ry != start[Y_AXIS]) {
            if (!inf_normalized_flag) {
              on_axis_distance = use_x_dist ? rx - start[X_AXIS] : ry - start[Y_AXIS];
              e_position = start[E_AXIS] + on_axis_distance * e_normalized_dist;
              z_position = start[Z_AXIS] + on_axis_distance * z_normalized_dist;
            }
            else {
              e_position = end[E_AXIS];
              z_position = end[Z_AXIS];
            }

            planner.buffer_segment(rx, ry, z_position + z0, e_position, feed_rate, extruder);
          } //else printf("FIRST MOVE PRUNED  ");
        }

        if (g26_debug_flag)
          debug_current_and_destination(PSTR("vertical move done in ubl.line_to_destination_cartesian()"));

        //
        // Check if we are at the final destination. Usually, we won't be, but if it is on a Y Mesh Line, we are done.
        //
        if (current_position[X_AXIS] != end[X_AXIS] || current_position[Y_AXIS] != end[Y_AXIS])
          goto FINAL_MOVE;

        set_current_from_destination();
        return;
      }

      /**
       *
       * This block handles horizontal lines. These are lines that stay within the same
       * Y Cell row. They do not need to be perfectly horizontal. They just can
       * not cross into another Y Cell row.
       *
       */

      if (dyi == 0) {             // Check for a horizontal line
        current_xi += left_flag;  // Line is heading left, we just want to go to the left
                                  // edge of this cell for the first move.
        while (current_xi != cell_dest_xi + left_flag) {
          current_xi += dxi;
          const float next_mesh_line_x = mesh_index_to_xpos(current_xi),
                      ry = m * next_mesh_line_x + c;   // Calculate Y at the next X mesh line

          float z0 = z_correction_for_y_on_vertical_mesh_line(ry, current_xi, current_yi)
                     * planner.fade_scaling_factor_for_z(end[Z_AXIS]);

          /**
           * If part of the Mesh is undefined, it will show up as NAN
           * in z_values[][] and propagate through the
           * calculations. If our correction is NAN, we throw it out
           * because part of the Mesh is undefined and we don't have the
           * information we need to complete the height correction.
           */
          if (isnan(z0)) z0 = 0.0;

          const float rx = mesh_index_to_xpos(current_xi);

          /**
           * Without this check, it is possible for the algorithm to generate a zero length move in the case
           * where the line is heading left and it is starting right on a Mesh Line boundary. For how often
           * that happens, it might be best to remove the check and always 'schedule' the move because
           * the planner.buffer_segment() routine will filter it if that happens.
           */
          if (rx != start[X_AXIS]) {
            if (!inf_normalized_flag) {
              on_axis_distance = use_x_dist ? rx - start[X_AXIS] : ry - start[Y_AXIS];
              e_position = start[E_AXIS] + on_axis_distance * e_normalized_dist;  // is based on X or Y because this is a horizontal move
              z_position = start[Z_AXIS] + on_axis_distance * z_normalized_dist;
            }
            else {
              e_position = end[E_AXIS];
              z_position = end[Z_AXIS];
            }

            planner.buffer_segment(rx, ry, z_position + z0, e_position, feed_rate, extruder);
          } //else printf("FIRST MOVE PRUNED  ");
        }

        if (g26_debug_flag)
          debug_current_and_destination(PSTR("horizontal move done in ubl.line_to_destination_cartesian()"));

        if (current_position[X_AXIS] != end[X_AXIS] || current_position[Y_AXIS] != end[Y_AXIS])
          goto FINAL_MOVE;

        set_current_from_destination();
        return;
      }

      /**
       *
       * This block handles the generic case of a line crossing both X and Y Mesh lines.
       *
       */

      int xi_cnt = cell_start_xi - cell_dest_xi,
          yi_cnt = cell_start_yi - cell_dest_yi;

      if (xi_cnt < 0) xi_cnt = -xi_cnt;
      if (yi_cnt < 0) yi_cnt = -yi_cnt;

      current_xi += left_flag;
      current_yi += down_flag;

      while (xi_cnt > 0 || yi_cnt > 0) {

        const float next_mesh_line_x = mesh_index_to_xpos(current_xi + dxi),
                    next_mesh_line_y = mesh_index_to_ypos(current_yi + dyi),
                    ry = m * next_mesh_line_x + c,   // Calculate Y at the next X mesh line
                    rx = (next_mesh_line_y - c) / m; // Calculate X at the next Y mesh line
                                                     // (No need to worry about m being zero.
                                                     //  If that was the case, it was already detected
                                                     //  as a vertical line move above.)

        if (left_flag == (rx > next_mesh_line_x)) { // Check if we hit the Y line first
          // Yes!  Crossing a Y Mesh Line next
          float z0 = z_correction_for_x_on_horizontal_mesh_line(rx, current_xi - left_flag, current_yi + dyi)
                     * planner.fade_scaling_factor_for_z(end[Z_AXIS]);

          /**
           * If part of the Mesh is undefined, it will show up as NAN
           * in z_values[][] and propagate through the
           * calculations. If our correction is NAN, we throw it out
           * because part of the Mesh is undefined and we don't have the
           * information we need to complete the height correction.
           */
          if (isnan(z0)) z0 = 0.0;

          if (!inf_normalized_flag) {
            on_axis_distance = use_x_dist ? rx - start[X_AXIS] : next_mesh_line_y - start[Y_AXIS];
            e_position = start[E_AXIS] + on_axis_distance * e_normalized_dist;
            z_position = start[Z_AXIS] + on_axis_distance * z_normalized_dist;
          }
          else {
            e_position = end[E_AXIS];
            z_position = end[Z_AXIS];
          }
          planner.buffer_segment(rx, next_mesh_line_y, z_position + z0, e_position, feed_rate, extruder);
          current_yi += dyi;
          yi_cnt--;
        }
        else {
          // Yes!  Crossing a X Mesh Line next
          float z0 = z_correction_for_y_on_vertical_mesh_line(ry, current_xi + dxi, current_yi - down_flag)
                     * planner.fade_scaling_factor_for_z(end[Z_AXIS]);

          /**
           * If part of the Mesh is undefined, it will show up as NAN
           * in z_values[][] and propagate through the
           * calculations. If our correction is NAN, we throw it out
           * because part of the Mesh is undefined and we don't have the
           * information we need to complete the height correction.
           */
          if (isnan(z0)) z0 = 0.0;

          if (!inf_normalized_flag) {
            on_axis_distance = use_x_dist ? next_mesh_line_x - start[X_AXIS] : ry - start[Y_AXIS];
            e_position = start[E_AXIS] + on_axis_distance * e_normalized_dist;
            z_position = start[Z_AXIS] + on_axis_distance * z_normalized_dist;
          }
          else {
            e_position = end[E_AXIS];
            z_position = end[Z_AXIS];
          }

          planner.buffer_segment(next_mesh_line_x, ry, z_position + z0, e_position, feed_rate, extruder);
          current_xi += dxi;
          xi_cnt--;
        }

        if (xi_cnt < 0 || yi_cnt < 0) break; // we've gone too far, so exit the loop and move on to FINAL_MOVE
      }

      if (g26_debug_flag)
        debug_current_and_destination(PSTR("generic move done in ubl.line_to_destination_cartesian()"));

      if (current_position[X_AXIS] != end[X_AXIS] || current_position[Y_AXIS] != end[Y_AXIS])
        goto FINAL_MOVE;

      set_current_from_destination();
    }