[MPL] Fixed storage order of property input

MaterialLib/MPL/Property.cpp

@@ -39,7 +39,9 @@ PropertyDataType fromVector(std::vector<double> const& values)
         case 4:
         {
             using M = Eigen::Matrix2d;
-            return M{Eigen::Map<M const>{values.data(), 2, 2}};
+            // the values vector is in row major order
+            using MRM = Eigen::Matrix<double, 2, 2, Eigen::RowMajor>;
+            return M{Eigen::Map<MRM const>{values.data(), 2, 2}};
         }
         case 6:
         {
@@ -50,7 +52,9 @@ PropertyDataType fromVector(std::vector<double> const& values)
         case 9:
         {
             using M = Eigen::Matrix3d;
-            return M{Eigen::Map<M const>{values.data(), 3, 3}};
+            // the values vector is in row major order
+            using MRM = Eigen::Matrix<double, 3, 3, Eigen::RowMajor>;
+            return M{Eigen::Map<MRM const>{values.data(), 3, 3}};
         }
         default:
         {

MaterialLib/MPL/Property.h

@@ -36,7 +36,12 @@ using PropertyDataType =
 
 /// Conversion of a vector to PropertyDataType for different sizes of the
 /// vector.
-/// \attention It cannot distinguish between 2x2 matrix and 4x1 vector.
+///
+/// \attention This method cannot distinguish between 2x2 matrix and 4x1 vector.
+///
+/// \note If the \c values vector stores all elements of a 2x2 or 3x3 matrix
+/// (i.e. the general case for 2x2 and 3x3 matrices), it is assumed to be in row
+/// major storage order.
 PropertyDataType fromVector(std::vector<double> const& values);
 
 /// This class is the base class for any material property of any