diff --git a/src/experimental/sf_sphere.scad b/src/experimental/sf_sphere.scad
index a3b92c85..d7f13b91 100644
--- a/src/experimental/sf_sphere.scad
+++ b/src/experimental/sf_sphere.scad
@@ -1,3 +1,4 @@
+use <experimental/_impl/_sf_square_surfaces.scad>;
 use <experimental/sf_solidify.scad>;
 use <experimental/tf_sphere.scad>;
 
@@ -9,38 +10,22 @@ use <experimental/tf_sphere.scad>;
     invert: inverts how the gray levels are translated into height values.
 */
 module sf_sphere(levels, radius, thickness, angle = [180, 360], invert = false) {
+    surface = _sf_square_surfaces(levels, thickness, invert);
     rows = len(levels);
     columns = len(levels[0]);
     size = [columns - 1, rows - 1];
 
-    surface1 = [
-        for(r = [0:rows - 1]) 
-        [
-            for(c = [0:columns - 1]) 
-            let(lv = invert ? 255 - levels[rows - r - 1][c] : levels[rows - r - 1][c])
-            [c, r, lv / 255 * thickness]
-        ]
-    ];
-
-    surface2 = [
-        for(r = [0:rows - 1]) 
-        [
-            for(c = [0:columns - 1]) 
-            [c, r, 0]
-        ]
-    ];
-
     offset_z = invert ? thickness : 0;
     sf_solidify(
         [
-            for(row = surface1) 
+            for(row = surface[0]) 
             [
                 for(p = row) tf_sphere(size, p, radius + offset_z, angle)
             ]
         ]
         ,
         [
-            for(row = surface2) 
+            for(row = surface[1]) 
             [
                 for(p = row) tf_sphere(size, p, radius, angle)
             ]