double Tetrahedra<ConcreteShape>::estimatedElementRadius() {
Matrix3d invJ;
double detJ;
std::tie(invJ, detJ) = ConcreteShape::inverseJacobian(mVtxCrd);
Matrix3d J = invJ.inverse();
VectorXcd eivals = J.eigenvalues();
// get minimum h (smallest direction)
Vector3d eivals_norm;
for(int i=0;i<3;i++) {
eivals_norm(i) = std::norm(eivals[i]);
}
return eivals_norm.minCoeff();
}
