Add EXTRAPOLATE_BEYOND_GRID option to bilinear leveling

Marlin/Configuration.h

@@ -825,6 +825,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/Marlin_main.cpp

@@ -10592,12 +10592,25 @@ void ok_to_send() {
     const float x = RAW_X_POSITION(logical[X_AXIS]) - bilinear_start[X_AXIS],
                 y = RAW_Y_POSITION(logical[Y_AXIS]) - bilinear_start[Y_AXIS];
 
+    #if ENABLED(EXTRAPOLATE_BEYOND_GRID)
+      // Keep using the last grid box
+      #define FAR_EDGE_OR_BOX 2
+    #else
+      // Just use the grid far edge
+      #define FAR_EDGE_OR_BOX 1
+    #endif
+
     if (last_x != x) {
       last_x = x;
       ratio_x = x * ABL_BG_FACTOR(X_AXIS);
-      const float gx = constrain(floor(ratio_x), 0, ABL_BG_POINTS_X - 1);
+      const float gx = constrain(floor(ratio_x), 0, ABL_BG_POINTS_X - FAR_EDGE_OR_BOX);
       ratio_x -= gx;      // Subtract whole to get the ratio within the grid box
+
+      #if DISABLED(EXTRAPOLATE_BEYOND_GRID)
+        // Beyond the grid maintain height at grid edges
         NOLESS(ratio_x, 0); // Never < 0.0. (> 1.0 is ok when nextx==gridx.)
+      #endif
+
       gridx = gx;
       nextx = min(gridx + 1, ABL_BG_POINTS_X - 1);
     }
@@ -10607,9 +10620,14 @@ void ok_to_send() {
       if (last_y != y) {
         last_y = y;
         ratio_y = y * ABL_BG_FACTOR(Y_AXIS);
-        const float gy = constrain(floor(ratio_y), 0, ABL_BG_POINTS_Y - 1);
+        const float gy = constrain(floor(ratio_y), 0, ABL_BG_POINTS_Y - FAR_EDGE_OR_BOX);
         ratio_y -= gy;
-        NOLESS(ratio_y, 0);
+
+        #if DISABLED(EXTRAPOLATE_BEYOND_GRID)
+          // Beyond the grid maintain height at grid edges
+          NOLESS(ratio_y, 0); // Never < 0.0. (> 1.0 is ok when nexty==gridy.)
+        #endif
+
         gridy = gy;
         nexty = min(gridy + 1, ABL_BG_POINTS_Y - 1);
       }

Marlin/example_configurations/Cartesio/Configuration.h

@@ -823,6 +823,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/Felix/Configuration.h

@@ -807,6 +807,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/Felix/DUAL/Configuration.h

@@ -807,6 +807,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/FolgerTech-i3-2020/Configuration.h

@@ -827,6 +827,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/Hephestos/Configuration.h

@@ -815,6 +815,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/Hephestos_2/Configuration.h

@@ -818,6 +818,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/K8200/Configuration.h

@@ -853,6 +853,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/K8400/Configuration.h

@@ -824,6 +824,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/K8400/Dual-head/Configuration.h

@@ -824,6 +824,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/RepRapWorld/Megatronics/Configuration.h

@@ -824,6 +824,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/RigidBot/Configuration.h

@@ -823,6 +823,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/SCARA/Configuration.h

@@ -839,6 +839,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/TAZ4/Configuration.h

@@ -844,6 +844,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/TinyBoy2/Configuration.h

@@ -880,6 +880,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/WITBOX/Configuration.h

@@ -815,6 +815,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/adafruit/ST7565/Configuration.h

@@ -824,6 +824,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/delta/FLSUN/auto_calibrate/Configuration.h

@@ -943,6 +943,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/delta/kossel_mini/Configuration.h

@@ -935,6 +935,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/delta/kossel_pro/Configuration.h

@@ -941,6 +941,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/gCreate_gMax1.5+/Configuration.h

@@ -809,6 +809,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/makibox/Configuration.h

@@ -827,6 +827,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/tvrrug/Round2/Configuration.h

@@ -820,6 +820,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.

Marlin/example_configurations/wt150/Configuration.h

@@ -829,6 +829,10 @@
 
   #if ENABLED(AUTO_BED_LEVELING_BILINEAR)
 
+    // Beyond the probed grid, continue the implied tilt?
+    // Default is to maintain the height of the nearest edge.
+    //#define EXTRAPOLATE_BEYOND_GRID
+
     //
     // Experimental Subdivision of the grid by Catmull-Rom method.
     // Synthesizes intermediate points to produce a more detailed mesh.