bed_mesh: Force bicubic when lagrange would fail

Author: jschuh

bed_mesh_fast.cfg

@@ -55,11 +55,21 @@ gcode:
                         (safe_max_y - safe_min_y) * probe_count_scale )
                         | round(0) | int %}
         {% set y_probes = ((y_probes, probe_min_count)|max, max_y_probes)|min %}
+        # Add probes for bicubic if one axis has too many probes for lagrange.
+        {% if x_probes > 6 and y_probes < 4 %}
+          {% set y_probes = 4 %}
+        {% elif y_probes > 6 and x_probes < 4 %}
+          {% set x_probes = 4 %}
+        {% endif %}
         {% set probe_count = [x_probes,y_probes] %}
     {% endif %}
     {% set dummy = params.__setitem__("MESH_MIN", mesh_min_x~","~mesh_min_y) %}
     {% set dummy = params.__setitem__("MESH_MAX", mesh_max_x~","~mesh_max_y) %}
     {% set dummy = params.__setitem__("PROBE_COUNT", probe_count|join(',')) %}
+    # Force bicubic if we've exceeded the max for lagrange.
+    {% if probe_count[0]|int > 6 or probe_count[1]|default(0)|int > 6 %}
+      {% set dummy = params.__setitem__("ALGORITHM", "bicubic") %}
+    {% endif %}
   {% endif %}
   {% if printer["gcode_macro bed_mesh_calibrate"].km_override|default(False) %}
     {% set calibrate_cmd = "_km_bed_mesh_calibrate_base" %}