diff --git a/ShoulderCase/@MaskSubdivider/MaskSubdivider.m b/ShoulderCase/@MaskSubdivider/MaskSubdivider.m
new file mode 100644
index 0000000..174271c
--- /dev/null
+++ b/ShoulderCase/@MaskSubdivider/MaskSubdivider.m
@@ -0,0 +1,50 @@
+classdef MaskSubdivider < handle
+
+  properties (Access = private)
+    % 10° slices
+    numberOfAngularDivisions = 36;
+    numberOfRadialDivisions = 10;
+    center
+    mask
+    maskPixelsAngle
+  end
+
+  methods 
+    function obj = MaskSubdivider(mask)
+      obj.mask = mask;
+      % default center is the middle of the mask
+      obj.center = round(size(obj.mask)/2);
+    end
+
+    function setNumberOfAngularDivisions(obj, value)
+      obj.numberOfAngularDivisions = value;
+    end
+
+    function setNumberOfRadialDivisions(obj, value)
+      obj.numberOfRadialDivisions = value;
+    end
+
+    function setCenterOfDivisions(obj, centerIndices)
+      obj.center = centerIndices;
+    end
+
+    function set.center(obj, value)
+      obj.center = value;
+      obj.maskPixelsAngle = obj.getMaskPixelsAngle();
+    end
+
+    function output = getMaskPixelsAngle(obj)
+      [maskColumnIndex, maskRowIndex] =...
+        meshgrid(1:size(obj.mask, 1), 1:size(obj.mask, 2));
+      maskColumnIndex = maskColumnIndex-obj.center(1);
+      maskRowIndex = maskRowIndex-obj.center(2);
+      normToCenter = sqrt(maskColumnIndex.^2 + maskRowIndex.^2);
+      maskPixelsAngle = acosd(maskColumnIndex./normToCenter);
+      maskSinus = maskRowIndex./normToCenter;
+      maskPixelsAngle(maskSinus < 0) =...
+        360 - maskPixelsAngle(maskSinus < 0);
+      output = maskPixelsAngle;
+    end
+  end
+
+end
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