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--- doc:user:elements:volumes:user_defined_materials [2024/06/06 15:53] – radermecker
+++ doc:user:elements:volumes:user_defined_materials [2024/10/22 14:15] (current) – radermecker
@@ Line 7: / Line 7: @@
   * ''def PythonHyperMaterial.<nowiki>__init__</nowiki>(self, _no):'' with ''_no'' being the material number chosen.
   * ''def computeStressPython(self, FTotal):''
-    * **Input:** The total deformation gradient ''FTotal'', sent from C++ to Python through a `std::vector` [F11, F12, F13, F21, F22, F23, F31, F32, F33]
+    * **Input:** The total deformation gradient ''FTotal'', sent from C++ to Python through a ''std::vector'' [F11, F12, F13, F21, F22, F23, F31, F32, F33], hence ''FTotal[0] = F11'', etc.
     * **Output:** The Cauchy stress, in the current configuration, returned from Python to C++ through a Python list [Sig11, Sig22, Sig33, Sig12, Sig13, Sig23]
@@ Line 13: / Line 13: @@
 <WRAP center round important 60%>
-So far, global perturbation (of the internal forces) must be used. Cfr.
+Selective integration with pressure report ''SRIPR'' for the integration will not work.
+</WRAP>
+<WRAP center round info 60%>
+The material tangent moduli is automatically approximated using finite central difference.
 </WRAP>
@@ Line 20: / Line 23: @@
 <code python>
 from wrap import *
+import numpy as np
 metafor = None
-class PythonHyperMaterial:
-    def __init__(self, _no):
-        self._no = _no
 class UserMat(PythonHyperMaterial):
@@ Line 53: / Line 53: @@
     elementsProps = ElementProperties(Volume2DElement)
     elementsProps.put(MATERIAL, 1)
-    elementsProps.put(STIFFMETHOD, STIFF_NUMERIC)
     # ... some code ... #