--- a
+++ b/Tools/ModelUtilities/SegmentCoM/CreateCoMRefNode.any
@@ -0,0 +1,93 @@
+/*
+---
+group: Utilities
+topic: Center of mass
+descr: |
+  Class template to create a reference node at the center of mass of a segment
+  with its axis aligned with the principal axes of inertia. 
+---
+
+To use the class template import the file:
+#include "<ANYBODY_PATH_MODELUTILS>/SegmentCoM/CreateCoMRefNode.any"
+
+*/
+
+
+// Creates a reference node at the center of mass of the segment. The orientation of the reference
+// node is determined from the principal axes of inertia, which are determined from the Jmatrix of
+// the segment. This class template must be used inside the scope of AnySeg.
+//
+// This class template calculates the Jmatrix about the center of mass and its eigenvectors and eigenvalues   
+// to determine the principal axes of inertia. In cases with symmetric shape, for example a sphere, 
+// cylinder, etc., some of the eigenvalue terms are duplicated. Therefore, the principal axes may not 
+// be uniquely defined in these cases.
+//
+// In the example below a reference node is created inside a segment.
+//
+// :::{rubric} Example
+// :::
+//
+// :::{code-block} AnyScriptDoc
+// AnySeg MySegment = {
+//   CreateCoMRefNode CoMNode () = {
+//     viewRefFrame.Visible = On;
+//   };
+// };
+//:::
+//
+#class_template CreateCoMRefNode (__CLASS__ = AnyRefNode,
+  SUPPRESS_SYMMETRY_NOTICE = "Off"){
+  // Arguments
+  // -----------
+  //  CreateCoMRefNode#SUPPRESS_SYMMETRY_NOTICE
+  //   Switch to suppress the notice detecting duplicate eigenvalues of the Jmatrix about the center of mass, 
+  //   indicating that two or three axes of the center of mass node may not be uniquely defined.
+
+  /// Jmatrix about the center of mass
+  AnyMat33 JMatrixCoM = .Jmatrix + .Mass*skewmat3d(.sCoM)*skewmat3d(.sCoM);
+  /// Matrix with eigenvectors and eigenvalues from the Jmatrix about center of mass
+  AnyMatrix JMatrixEV = LAPACK_syevd(JMatrixCoM,"V","V");
+  /// Eigenvectors of the Jmatrix about the center of mass
+  AnyFloat EigenVectors = {JMatrixEV[0],JMatrixEV[1],JMatrixEV[2]};
+  /// Eigenvalues of the Jmatrix about the center of mass
+  AnyFloat EigenValues = JMatrixEV[3];
+  
+  #if SUPPRESS_SYMMETRY_NOTICE == "Off"
+  /// Check if first and second eigenvalues are same
+  AnyInt test0_1 = iffun(ltfun(abs(EigenValues[0]-EigenValues[1]),SymmetryTolerance),1,0);
+  /// Check if second and third eigenvalues are same
+  AnyInt test1_2 = iffun(ltfun(abs(EigenValues[1]-EigenValues[2]),SymmetryTolerance),1,0);
+  /// Check if first and third eigenvalues are same
+  AnyInt test0_2 = iffun(ltfun(abs(EigenValues[0]-EigenValues[2]),SymmetryTolerance),1,0);
+  /// Sum of the three tests.
+  AnyInt sumcheck = test0_1+test1_2+test0_2;
+  /// Notice when 2 Eigenvalues are same
+  AnyInt AxisNotice_2 = notice(sumcheck-1, strformat("2 of 3 eigenvalues are the same. 2 axes of the Center of Mass node may not be uniquely defined due to symmetric moment of inertia about 2 axes.\n\t\t\tYou can suppress this notice by setting SUPPRESS_SYMMETRY_NOTICE = " + strquote("On")));
+  /// Notice when 3 Eigenvalues are same
+  AnyInt AxisNotice_3 = notice(sumcheck-3, strformat("3 of 3 eigenvalues are the same. The axes of the Center of Mass node may not be uniquely defined due to symmetric moment of inertia about 3 axes. \n\t\t\tYou can suppress this notice by setting SUPPRESS_SYMMETRY_NOTICE = " + strquote("On")));
+  #endif
+  
+  //CreateCoMRefNode
+  /// Tolerance for checking duplicate eigenvalues
+  #var AnyFloat SymmetryTolerance = 1e-10;
+  
+  // sRel
+  /// Relative position of the reference node in the segmental frame. This defaults to
+  /// segment sCoM.
+  #var sRel = .sCoM;
+  // ARel 
+  /// Relative orientation of the reference node in the segmental frame. This defaults to
+  /// be aligned with the principal axes of inertia.
+  #var ARel = {EigenVectors[0],EigenVectors[1],cross(EigenVectors[0],EigenVectors[1])}';
+  viewRefFrame = {
+    // viewRefFrame.Visible
+    /// Switch to view the reference node.
+    #var Visible = Off;
+    // viewRefFrame.ScaleXYZ
+    /// Size of the drawing of the reference node.
+    #var ScaleXYZ = 0.5*{1,1,1};
+    // viewRefFrame.RGB
+    /// Color of the drawing of the reference node.
+    #var RGB = {0.8,0.2,0.2};
+  };
+};
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