double
compute_deformed_length(node_set& nodes, EquationSystems* equation_systems)
{
System& X_system = equation_systems->get_system<System>(IBFEMethod::COORDS_SYSTEM_NAME);
const unsigned int X_sys_num = X_system.number();
NumericVector<double>* X_vec = X_system.solution.get();
AutoPtr<NumericVector<Number> > X_serial_vec = NumericVector<Number>::build(X_vec->comm());
X_serial_vec->init(X_vec->size(), true, SERIAL);
X_vec->localize(*X_serial_vec);
// Get the current positions of the points.
std::vector<IBTK::Point> points;
points.reserve(nodes.size());
IBTK::Point p;
for (typename node_set::iterator it = nodes.begin(); it != nodes.end(); ++it)
{
Node* node = *it;
for (unsigned int d = 0; d < NDIM; ++d)
{
p(d) = (*X_serial_vec)(node->dof_number(X_sys_num, d, 0));
}
points.push_back(p);
}
// Compute the length of the center line.
IBTK::Point p0, p1;
double l = 0.0;
std::vector<IBTK::Point>::iterator it = points.begin();
p0 = *it;
++it;
for (; it != points.end(); ++it)
{
p1 = *it;
double l_segment_sq = 0.0;
for (int d = 0; d < NDIM; ++d)
{
l_segment_sq += pow(p0(d) - p1(d), 2.0);
}
l += sqrt(l_segment_sq);
p0 = p1;
}
return l;
}
double
compute_displaced_area(node_set& nodes, EquationSystems* equation_systems)
{
System& X_system = equation_systems->get_system<System>(IBFEMethod::COORDS_SYSTEM_NAME);
const unsigned int X_sys_num = X_system.number();
NumericVector<double>* X_vec = X_system.solution.get();
AutoPtr<NumericVector<Number> > X_serial_vec = NumericVector<Number>::build(X_vec->comm());
X_serial_vec->init(X_vec->size(), true, SERIAL);
X_vec->localize(*X_serial_vec);
// Get the current positions of the points.
std::vector<IBTK::Point> points;
points.reserve(nodes.size());
IBTK::Point p;
for (typename node_set::iterator it = nodes.begin(); it != nodes.end(); ++it)
{
Node* node = *it;
for (unsigned int d = 0; d < NDIM; ++d)
{
p(d) = (*X_serial_vec)(node->dof_number(X_sys_num, d, 0));
}
points.push_back(p);
}
// Compute the area of the polygon.
IBTK::Point p0, p1;
double A2 = 0.0;
p0 = *points.rbegin();
for (std::vector<IBTK::Point>::iterator it = points.begin(); it != points.end(); ++it)
{
p1 = *it;
A2 += p0(0) * p1(1) - p0(1) * p1(0);
p0 = p1;
}
return 0.5 * abs(A2);
}