ENH: snappyHexMesh: detect small distance snapping

applications/utilities/mesh/generation/snappyHexMesh/snappyHexMesh.C

@@ -1312,8 +1312,16 @@ int main(int argc, char *argv[])
 
         // Use the resolveFeatureAngle from the refinement parameters
         scalar curvature = refineParams.curvature();
+        scalar planarAngle = refineParams.planarAngle();
 
-        snapDriver.doSnap(snapDict, motionDict, curvature, snapParams);
+        snapDriver.doSnap
+        (
+            snapDict,
+            motionDict,
+            curvature,
+            planarAngle,
+            snapParams
+        );
 
         writeMesh
         (

applications/utilities/mesh/generation/snappyHexMesh/snappyHexMeshDict

@@ -194,10 +194,13 @@ castellatedMeshControls
 
     // Planar angle:
     // - used to determine if surface normals
-    //   are roughly the same or opposite. Used e.g. in proximity refinement
-    //   and to decide when to merge free-standing baffles
-    //   If e.g. running in surfaceSimplify mode set this to 180 to
-    //   merge all baffles
+    //   are roughly the same or opposite. Used
+    //      - in proximity refinement
+    //      - to decide when to merge free-standing baffles
+    //        (if e.g. running in surfaceSimplify mode set this to 180 to
+    //         merge all baffles)
+    //      - in snapping to avoid snapping to nearest on 'wrong' side
+    //        of thin gap
     //
     // If not specified same as resolveFeatureAngle
     planarAngle 30;
@@ -284,6 +287,10 @@ snapControls
         // Detect features between multiple surfaces
         // (only for explicitFeatureSnap, default = false)
         multiRegionFeatureSnap false;
+
+
+    // wip: disable snapping to opposite near surfaces (revert to 22x behaviour)
+    // detectNearSurfacesSnap false;
 }
 
 // Settings for the layer addition.