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MeshFlatteningLscmRelax.cpp
719 lines (633 loc) · 25.2 KB
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MeshFlatteningLscmRelax.cpp
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/***************************************************************************
* Copyright (c) 2017 Lorenz Lechner *
* *
* This file is part of the FreeCAD CAx development system. *
* *
* This library is free software; you can redistribute it and/or *
* modify it under the terms of the GNU Library General Public *
* License as published by the Free Software Foundation; either *
* version 2 of the License, or (at your option) any later version. *
* *
* This library is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU Library General Public License for more details. *
* *
* You should have received a copy of the GNU Library General Public *
* License along with this library; see the file COPYING.LIB. If not, *
* write to the Free Software Foundation, Inc., 59 Temple Place, *
* Suite 330, Boston, MA 02111-1307, USA *
* *
***************************************************************************/
#include "PreCompiled.h"
#ifndef _PreComp_
#include <array>
#include <cmath>
#include <iostream>
#include <map>
#include <set>
#include <vector>
#endif
#ifndef M_PI
#define M_PI 3.14159265358979323846f
#endif
#include <Eigen/SparseCholesky>
#include "MeshFlatteningLscmRelax.h"
// TODO:
// area constrained (scale the final unwrapped mesh to the original area)
// FEM approach
// clang-format off
namespace lscmrelax
{
using trip = Eigen::Triplet<double>;
using spMat = Eigen::SparseMatrix<double>;
ColMat<double, 2> map_to_2D(ColMat<double, 3> points)
{
ColMat<double, 4> mat(points.size(), 4);
mat << points, ColMat<double, 1>::Ones(points.size());
Eigen::JacobiSVD<Eigen::MatrixXd> svd(mat, Eigen::ComputeThinU | Eigen::ComputeThinV);
Vector3 n = svd.matrixV().row(2);
n.normalize();
Vector3 y(0, 1, 0);
if ((n - y).norm() < 0.0001)
y = Vector3(1, 0, 0);
Vector3 x = n.cross(y);
x.normalize();
y = n.cross(x);
Eigen::Matrix<double, 3, 2> transform;
transform.col(0) = x;
transform.col(1) = y;
return points * transform;
}
unsigned int get_max_distance(Vector3 point, RowMat<double, 3> vertices, double & max_dist)
{
max_dist = 0;
double dist;
unsigned long max_dist_index = 0;
long j = 0;
for (j=0; j < vertices.cols(); j++)
{
// debugging
dist = (point - vertices.col(j)).norm();
if (dist > max_dist)
{
max_dist = dist;
max_dist_index = j;
}
}
return max_dist_index;
}
LscmRelax::LscmRelax(
RowMat<double, 3> vertices,
RowMat<long, 3> triangles,
std::vector<long> fixed_pins)
{
this->vertices = vertices;
this->triangles = triangles;
this->flat_vertices.resize(2, this->vertices.cols());
this->fixed_pins = fixed_pins;
// set the fixed pins of the flat-mesh:
this->set_fixed_pins();
unsigned int fixed_count = 0;
for (long i=0; i < this->vertices.cols(); i++)
{
if (fixed_count < this->fixed_pins.size())
{
if (i == this->fixed_pins[fixed_count])
fixed_count ++;
else
this->old_order.push_back(i);
}
else
this->old_order.push_back(i);
}
for (auto fixed_index: this->fixed_pins)
this->old_order.push_back(fixed_index);
// get the reversed map:
this->new_order.resize(this->old_order.size());
long j = 0;
for (auto index: this->old_order)
{
this->new_order[index] = j;
j++;
}
// set the C-mat
this->C << 1, nue, 0,
nue, 1, 0,
0, 0, (1 - nue) / 2;
this->C *= elasticity / (1 - nue * nue);
}
//////////////////////////////////////////////////////////////////////////
///////////////// F.E.M /////////////
//////////////////////////////////////////////////////////////////////////
void LscmRelax::relax(double weight)
{
ColMat<double, 3> d_q_l_g = this->q_l_m - this->q_l_g;
// for every triangle
Eigen::Matrix<double, 3, 6> B;
Eigen::Matrix<double, 2, 2> T;
Eigen::Matrix<double, 6, 6> K_m;
Eigen::Matrix<double, 6, 1> u_m, rhs_m;
Eigen::VectorXd rhs(this->vertices.cols() * 2 + 3);
if (this->sol.size() == 0)
this->sol.Zero(this->vertices.cols() * 2 + 3);
spMat K_g(this->vertices.cols() * 2 + 3, this->vertices.cols() * 2 + 3);
std::vector<trip> K_g_triplets;
Vector2 v1, v2, v3, v12, v23, v31;
long row_pos, col_pos;
double A;
rhs.setZero();
for (long i=0; i<this->triangles.cols(); i++)
{
// 1: construct B-mat in m-system
v1 = this->flat_vertices.col(this->triangles(0, i));
v2 = this->flat_vertices.col(this->triangles(1, i));
v3 = this->flat_vertices.col(this->triangles(2, i));
v12 = v2 - v1;
v23 = v3 - v2;
v31 = v1 - v3;
B << -v23.y(), 0, -v31.y(), 0, -v12.y(), 0,
0, v23.x(), 0, v31.x(), 0, v12.x(),
-v23.x(), v23.y(), -v31.x(), v31.y(), -v12.x(), v12.y();
T << v12.x(), -v12.y(),
v12.y(), v12.x();
T /= v12.norm();
A = std::abs(this->q_l_m(i, 0) * this->q_l_m(i, 2) / 2);
B /= A * 2; // (2*area)
// 2: sigma due dqlg in m-system
u_m << Vector2(0, 0), T * Vector2(d_q_l_g(i, 0), 0), T * Vector2(d_q_l_g(i, 1), d_q_l_g(i, 2));
// 3: rhs_m = B.T * C * B * dqlg_m
// K_m = B.T * C * B
rhs_m = B.transpose() * this->C * B * u_m * A;
K_m = B.transpose() * this->C * B * A;
// 5: add to rhs_g, K_g
for (int j=0; j < 3; j++)
{
row_pos = this->triangles(j, i);
rhs[row_pos * 2] += rhs_m[j * 2];
rhs[row_pos * 2 + 1] += rhs_m[j * 2 +1];
for (int k=0; k < 3; k++)
{
col_pos = this->triangles(k, i);
K_g_triplets.emplace_back(trip(row_pos * 2, col_pos * 2, K_m(j * 2, k * 2)));
K_g_triplets.emplace_back(trip(row_pos * 2 + 1, col_pos * 2, K_m(j * 2 + 1, k * 2)));
K_g_triplets.emplace_back(trip(row_pos * 2 + 1, col_pos * 2 + 1, K_m(j * 2 + 1, k * 2 + 1)));
K_g_triplets.emplace_back(trip(row_pos * 2, col_pos * 2 + 1, K_m(j * 2, k * 2 + 1)));
// we don't have to fill all because the matrix is symmetric.
}
}
}
// FIXING SOME PINS:
// - if there are no pins (or only one pin) selected solve the system without the nullspace solution.
// - if there are some pins selected, delete all columns, rows that refer to this pins
// set the diagonal element of these pins to 1 + the rhs to zero
// (? is it possible to fix in the inner of the face? for sure for fem, but lscm could have some problems)
// (we also need some extra variables to see if the pins come from user)
// fixing some points
// although only internal forces are applied there has to be locked
// at least 3 degrees of freedom to stop the mesh from pure rotation and pure translation
// std::vector<long> fixed_dof;
// fixed_dof.push_back(this->triangles(0, 0) * 2); //x0
// fixed_dof.push_back(this->triangles(0, 0) * 2 + 1); //y0
// fixed_dof.push_back(this->triangles(1, 0) * 2 + 1); // y1
// align flat mesh to fixed edge
// Vector2 edge = this->flat_vertices.col(this->triangles(1, 0)) -
// this->flat_vertices.col(this->triangles(0, 0));
// edge.normalize();
// Eigen::Matrix<double, 2, 2> rot;
// rot << edge.x(), edge.y(), -edge.y(), edge.x();
// this->flat_vertices = rot * this->flat_vertices;
// // return true if triplet row / col is in fixed_dof
// auto is_in_fixed_dof = [fixed_dof](const trip & element) -> bool {
// return (
// (std::find(fixed_dof.begin(), fixed_dof.end(), element.row()) != fixed_dof.end()) or
// (std::find(fixed_dof.begin(), fixed_dof.end(), element.col()) != fixed_dof.end()));
// };
// std::cout << "size of triplets: " << K_g_triplets.size() << std::endl;
// K_g_triplets.erase(
// std::remove_if(K_g_triplets.begin(), K_g_triplets.end(), is_in_fixed_dof),
// K_g_triplets.end());
// std::cout << "size of triplets: " << K_g_triplets.size() << std::endl;
// for (long fixed: fixed_dof)
// {
// K_g_triplets.push_back(trip(fixed, fixed, 1.));
// rhs[fixed] = 0;
// }
// for (long i=0; i< this->vertices.cols() * 2; i++)
// K_g_triplets.push_back(trip(i, i, 0.01));
// lagrange multiplier
for (long i=0; i < this->flat_vertices.cols() ; i++)
{
// fixing total ux
K_g_triplets.emplace_back(trip(i * 2, this->flat_vertices.cols() * 2, 1));
K_g_triplets.emplace_back(trip(this->flat_vertices.cols() * 2, i * 2, 1));
// fixing total uy
K_g_triplets.emplace_back(trip(i * 2 + 1, this->flat_vertices.cols() * 2 + 1, 1));
K_g_triplets.emplace_back(trip(this->flat_vertices.cols() * 2 + 1, i * 2 + 1, 1));
// fixing ux*y-uy*x
K_g_triplets.emplace_back(trip(i * 2, this->flat_vertices.cols() * 2 + 2, - this->flat_vertices(1, i)));
K_g_triplets.emplace_back(trip(this->flat_vertices.cols() * 2 + 2, i * 2, - this->flat_vertices(1, i)));
K_g_triplets.emplace_back(trip(i * 2 + 1, this->flat_vertices.cols() * 2 + 2, this->flat_vertices(0, i)));
K_g_triplets.emplace_back(trip(this->flat_vertices.cols() * 2 + 2, i * 2 + 1, this->flat_vertices(0, i)));
}
// project out the nullspace solution:
// Eigen::VectorXd nullspace1(this->flat_vertices.cols() * 2);
// Eigen::VectorXd nullspace2(this->flat_vertices.cols() * 2);
// nullspace1.setZero();
// nullspace2.setOnes();
// for (long i= 0; i < this->flat_vertices.cols(); i++)
// {
// nullspace1(i) = 1;
// nullspace2(i) = 0;
// }
// nullspace1.normalize();
// nullspace2.normalize();
// rhs -= nullspace1.dot(rhs) * nullspace1;
// rhs -= nullspace2.dot(rhs) * nullspace2;
K_g.setFromTriplets(K_g_triplets.begin(), K_g_triplets.end());
// rhs += K_g * Eigen::VectorXd::Ones(K_g.rows());
// solve linear system (privately store the value for guess in next step)
Eigen::SimplicialLDLT<spMat, Eigen::Lower> solver;
solver.compute(K_g);
this->sol = solver.solve(-rhs);
this->set_shift(this->sol.head(this->vertices.cols() * 2) * weight);
this->set_q_l_m();
}
void LscmRelax::area_relax(double weight)
{
// TODO: doesn't work so far
if (this->sol.size() == 0)
this->sol.Zero(this->vertices.cols());
std::vector<trip> K_g_triplets;
spMat K_g(this->vertices.cols() * 2, this->vertices.cols() * 2);
spMat K_g_lsq(this->triangles.cols(), this->vertices.cols() * 2);
Eigen::VectorXd rhs_lsq(this->triangles.cols());
Eigen::VectorXd rhs(this->vertices.cols() * 2);
rhs.setZero();
Eigen::Matrix<double, 1, 6> B;
double delta_a;
Vector2 v1, v2, v3, v12, v23, v31;
for (long i=0; i<this->triangles.cols(); i++)
{
// 1: construct B-mat in m-system
v1 = this->flat_vertices.col(this->triangles(0, i));
v2 = this->flat_vertices.col(this->triangles(1, i));
v3 = this->flat_vertices.col(this->triangles(2, i));
v12 = v2 - v1;
v23 = v3 - v2;
v31 = v1 - v3;
B << -v23.y(), v23.x(), -v31.y(), v31.x(), -v12.y(), v12.x();
delta_a = fabs(this->q_l_g(i, 0) * this->q_l_g(i, 2)) -
fabs(this->q_l_m(i, 0) * this->q_l_m(i, 2));
rhs_lsq[i] = delta_a * 0.1;
std::array<int, 6> range_6 {{0, 1, 2, 3, 4, 5}};
std::array<long, 6> indices;
for (int index=0; index<3; index++)
{
indices[index * 2] = this->triangles(index, i) * 2;
indices[index * 2 + 1] = this->triangles(index, i) * 2 + 1;
}
for(auto col: range_6)
{
K_g_triplets.emplace_back(trip(i, indices[col], (double) B[col]));
}
}
K_g_lsq.setFromTriplets(K_g_triplets.begin(), K_g_triplets.end());
K_g_triplets.clear();
K_g.setFromTriplets(K_g_triplets.begin(), K_g_triplets.end());
Eigen::ConjugateGradient<spMat> solver;
solver.compute(K_g);
this->sol = solver.solve(-rhs);
this->set_shift(this->sol * weight);
}
void LscmRelax::edge_relax(double weight)
{
// 1. get all edges
std::set<std::array<long, 2>> edges;
std::array<long, 2> edge;
for(long i=0; i<this->triangles.cols(); i++)
{
for(int j=0; j<3; j++)
{
long k = j+1;
if (k==3)
k = 0;
if (this->triangles(j, i) < this->triangles(k, i))
edge = std::array<long, 2>{{this->triangles(j, i), this->triangles(k, i)}};
else
edge = std::array<long, 2>{{this->triangles(k, i), this->triangles(j, i)}};
edges.insert(edge);
}
}
// 2. create system
if (this->sol.size() == 0)
this->sol.Zero(this->vertices.cols());
std::vector<trip> K_g_triplets;
spMat K_g(this->vertices.cols() * 2, this->vertices.cols() * 2);
Eigen::VectorXd rhs(this->vertices.cols() * 2);
rhs.setZero();
for(auto edge : edges)
{
// this goes to the right side
Vector3 v1_g = this->vertices.col(edge[0]);
Vector3 v2_g = this->vertices.col(edge[1]);
Vector2 v1_l = this->flat_vertices.col(edge[0]);
Vector2 v2_l = this->flat_vertices.col(edge[1]);
std::vector<int> range_4 {0, 1, 2, 3};
std::vector<long> indices {edge[0] * 2, edge[0] * 2 + 1, edge[1] * 2, edge[1] * 2 + 1};
double l_g = (v2_g - v1_g).norm();
double l_l = (v2_l - v1_l).norm();
Vector2 t = (v2_l - v1_l); // direction
t.normalize();
Eigen::Matrix<double, 1, 4> B;
Eigen::Matrix<double, 4, 4> K;
Eigen::Matrix<double, 4, 1> rhs_m;
B << -t.x(), -t.y(), t.x(), t.y();
K = 1. / l_g * B.transpose() * B;
rhs_m = - B.transpose() * (l_g - l_l);
for(auto row: range_4)
{
for (auto col: range_4)
{
K_g_triplets.emplace_back(trip(indices[row], indices[col], (double) K(row, col)));
}
rhs(indices[row]) += rhs_m[row];
}
}
K_g.setFromTriplets(K_g_triplets.begin(), K_g_triplets.end());
Eigen::ConjugateGradient<spMat,Eigen::Lower, NullSpaceProjector> solver;
solver.preconditioner().setNullSpace(this->get_nullspace());
solver.compute(K_g);
this->sol = solver.solve(-rhs);
this->set_shift(this->sol * weight);
}
//////////////////////////////////////////////////////////////////////////
///////////////// L.S.C.M /////////////
//////////////////////////////////////////////////////////////////////////
void LscmRelax::lscm()
{
this->set_q_l_g();
std::vector<trip> triple_list;
long i;
double x21, x31, y31, x32;
// 1. create the triplet list (t * 2, v * 2)
for(i=0; i<this->triangles.cols(); i++)
{
x21 = this->q_l_g(i, 0);
x31 = this->q_l_g(i, 1);
y31 = this->q_l_g(i, 2);
x32 = x31 - x21;
triple_list.emplace_back(trip(2 * i, this->new_order[this->triangles(0, i)] * 2, x32));
triple_list.emplace_back(trip(2 * i, this->new_order[this->triangles(0, i)] * 2 + 1, -y31));
triple_list.emplace_back(trip(2 * i, this->new_order[this->triangles(1, i)] * 2, -x31));
triple_list.emplace_back(trip(2 * i, this->new_order[this->triangles(1, i)] * 2 + 1, y31));
triple_list.emplace_back(trip(2 * i, this->new_order[this->triangles(2, i)] * 2, x21));
triple_list.emplace_back(trip(2 * i + 1, this->new_order[this->triangles(0, i)] * 2, y31));
triple_list.emplace_back(trip(2 * i + 1, this->new_order[this->triangles(0, i)] * 2 + 1, x32));
triple_list.emplace_back(trip(2 * i + 1, this->new_order[this->triangles(1, i)] * 2, -y31));
triple_list.emplace_back(trip(2 * i + 1, this->new_order[this->triangles(1, i)] * 2 + 1, -x31));
triple_list.emplace_back(trip(2 * i + 1, this->new_order[this->triangles(2, i)] * 2 + 1, x21));
}
// 2. divide the triplets in matrix(unknown part) and rhs(known part) and reset the position
std::vector<trip> rhs_triplets;
std::vector<trip> mat_triplets;
for (auto triplet: triple_list)
{
if (triplet.col() > static_cast<int>((this->vertices.cols() - this->fixed_pins.size()) * 2 - 1))
rhs_triplets.push_back(triplet);
else
mat_triplets.push_back(triplet);
}
// 3. create a rhs_pos vector
Eigen::VectorXd rhs_pos(this->vertices.cols() * 2);
rhs_pos.setZero();
for (auto index: this->fixed_pins)
{
rhs_pos[this->new_order[index] * 2] = this->flat_vertices(0, index); //TODO: not yet set
rhs_pos[this->new_order[index] * 2 + 1] = this->flat_vertices(1, index);
}
// 4. fill a sparse matrix and calculdate the rhs
Eigen::VectorXd rhs(this->triangles.cols() * 2); // maybe use a sparse vector
spMat B(this->triangles.cols() * 2, this->vertices.cols() * 2);
B.setFromTriplets(rhs_triplets.begin(), rhs_triplets.end());
rhs = B * rhs_pos;
// 5. create the lhs matrix
spMat A(this->triangles.cols() * 2, (this->vertices.cols() - this->fixed_pins.size()) * 2);
A.setFromTriplets(mat_triplets.begin(), mat_triplets.end());
// 6. solve the system and set the flatted coordinates
// Eigen::SparseQR<spMat, Eigen::COLAMDOrdering<int> > solver;
Eigen::LeastSquaresConjugateGradient<spMat > solver;
Eigen::VectorXd sol(this->vertices.size() * 2);
solver.compute(A);
sol = solver.solve(-rhs);
// TODO: create function, is needed also in the fem step
this->set_position(sol);
this->set_q_l_m();
this->transform(true);
// this->rotate_by_min_bound_area();
this->set_q_l_m();
}
void LscmRelax::set_q_l_g()
{
// get the coordinates of a triangle in local coordinates from the 3d mesh
// x1, y1, y2 = 0
// -> vector<x2, x3, y3>
this->q_l_g.resize(this->triangles.cols(), 3);
for (long i = 0; i < this->triangles.cols(); i++)
{
Vector3 r1 = this->vertices.col(this->triangles(0, i));
Vector3 r2 = this->vertices.col(this->triangles(1, i));
Vector3 r3 = this->vertices.col(this->triangles(2, i));
Vector3 r21 = r2 - r1;
Vector3 r31 = r3 - r1;
double r21_norm = r21.norm();
r21.normalize();
// if triangle is fliped this gives wrong results?
this->q_l_g.row(i) << r21_norm, r31.dot(r21), r31.cross(r21).norm();
}
}
void LscmRelax::set_q_l_m()
{
// get the coordinates of a triangle in local coordinates from the 2d map
// x1, y1, y2 = 0
// -> vector<x2, x3, y3>
this->q_l_m.resize(this->triangles.cols(), 3);
for (long i = 0; i < this->triangles.cols(); i++)
{
Vector2 r1 = this->flat_vertices.col(this->triangles(0, i));
Vector2 r2 = this->flat_vertices.col(this->triangles(1, i));
Vector2 r3 = this->flat_vertices.col(this->triangles(2, i));
Vector2 r21 = r2 - r1;
Vector2 r31 = r3 - r1;
double r21_norm = r21.norm();
r21.normalize();
// if triangle is fliped this gives wrong results!
this->q_l_m.row(i) << r21_norm, r31.dot(r21), -(r31.x() * r21.y() - r31.y() * r21.x());
}
}
void LscmRelax::set_fixed_pins()
{
// if less then one fixed pin is set find two by an automated algorithm and align them to y = 0
// if more then two pins are chosen find a leastsquare-plane and project the points on it
// insert the points in the flat-vertices vector
if (this->fixed_pins.size() == 0)
this->fixed_pins.push_back(0);
if (this->fixed_pins.size() == 1)
{
double dist;
this->fixed_pins.push_back(get_max_distance(this->vertices.col(this->fixed_pins[0]), this->vertices, dist));
this->flat_vertices.col(this->fixed_pins[0]) = Vector2(0, 0);
this->flat_vertices.col(this->fixed_pins[1]) = Vector2(dist, 0);
}
std::sort(this->fixed_pins.begin(), this->fixed_pins.end());
// not yet working
// if (this->fixed_pins.size() > 2)
// {
// std::vector<Vector3> fixed_3d_points;
// for (unsigned int index: this->fixed_pins)
// fixed_3d_points.push_back(this->vertices[index]);
// std::vector<Vector2> maped_points = map_to_2D(fixed_3d_points);
// unsigned int i = 0;
// for (unsigned int index: this->fixed_pins)
// {
// this->flat_vertices[i] = maped_points[i];
// i++;
// }
// }
}
ColMat<double, 3> LscmRelax::get_flat_vertices_3D()
{
ColMat<double, 2> mat = this->flat_vertices.transpose();
ColMat<double, 3> mat3d(mat.rows(), 3);
mat3d << mat, ColMat<double, 1>::Zero(mat.rows());
return mat3d;
}
void LscmRelax::set_position(Eigen::VectorXd sol)
{
for (long i=0; i < this->vertices.size(); i++)
{
if (sol.size() > i * 2 + 1)
this->flat_vertices.col(this->old_order[i]) << sol[i * 2], sol[i * 2 + 1];
}
}
void LscmRelax::set_shift(Eigen::VectorXd sol)
{
for (long i=0; i < this->vertices.size(); i++)
{
if (sol.size() > i * 2 + 1)
this->flat_vertices.col(i) += Vector2(sol[i * 2], sol[i * 2 + 1]);
}
}
double LscmRelax::get_area()
{
double area = 0;
for(long i = 0; i < this->triangles.cols(); i++)
{
area += this->q_l_g(i, 0) * this->q_l_g(i, 2);
}
return area / 2;
}
double LscmRelax::get_flat_area()
{
double area = 0;
for(long i = 0; i < this->triangles.cols(); i++)
{
area += this->q_l_m(i, 0) * this->q_l_m(i, 2);
}
return area / 2;
}
void LscmRelax::transform(bool scale)
{
// assuming q_l_m and flat_vertices are set
Vector2 weighted_center, center;
weighted_center.setZero();
double flat_area = 0;
double global_area = 0;
double element_area;
for(long i = 0; i < this->triangles.cols(); i++)
{
global_area += this->q_l_g(i, 0) * this->q_l_g(i, 2) / 2;
element_area = this->q_l_m(i, 0) * this->q_l_m(i, 2) / 2;
for (int j=0; j < 3; j++)
weighted_center += this->flat_vertices.col(this->triangles(j, i)) * element_area / 3;
flat_area += element_area;
}
center = weighted_center / flat_area;
for (long i = 0; i < this->flat_vertices.cols(); i++)
this->flat_vertices.col(i) -= center;
if (scale)
this->flat_vertices *= std::pow(global_area / flat_area, 0.5);
this->set_q_l_m();
}
void LscmRelax::rotate_by_min_bound_area()
{
int n = 100;
double phi;
double min_phi = 0;
double min_area = 0;
bool x_dominant = false;
// rotate vector by 90 degree and find min area
for (int i = 0; i < n + 1; i++ )
{
phi = i * M_PI / n;
Eigen::VectorXd x_proj = this->flat_vertices.transpose() * Vector2(std::cos(phi), std::sin(phi));
Eigen::VectorXd y_proj = this->flat_vertices.transpose() * Vector2(-std::sin(phi), std::cos(phi));
double x_distance = x_proj.maxCoeff() - x_proj.minCoeff();
double y_distance = y_proj.maxCoeff() - y_proj.minCoeff();
double area = x_distance * y_distance;
if (min_area == 0 || area < min_area)
{
min_area = area;
min_phi = phi;
x_dominant = x_distance > y_distance;
}
}
Eigen::Matrix<double, 2, 2> rot;
min_phi += x_dominant * M_PI / 2;
rot << std::cos(min_phi), std::sin(min_phi), -std::sin(min_phi), std::cos(min_phi);
this->flat_vertices = rot * this->flat_vertices;
}
std::vector<long> LscmRelax::get_fem_fixed_pins()
{
long min_x_index = 0;
double min_x = this->vertices(0, 0);
for (long i=0; i<this->flat_vertices.cols(); i++)
{
// get index with min x
if (this->flat_vertices(0, i) < min_x)
{
min_x = this->flat_vertices(0, i);
min_x_index = i;
}
}
double min_y = this->flat_vertices(1, min_x_index);
long max_x_index = 0;
double max_x = 0;
for (long i=0; i<this->flat_vertices.cols(); i++)
{
// get index with min x
double d_x = (this->flat_vertices(0, i) - min_x);
double d_y = (this->flat_vertices(1, i) - min_y);
if (d_x * d_x - d_y * d_y > max_x)
{
max_x = d_x * d_x - d_y * d_y;
max_x_index = i;
}
}
return std::vector<long>{min_x_index * 2, min_x_index * 2 + 1, max_x_index * 2 + 1};
}
Eigen::MatrixXd LscmRelax::get_nullspace()
{
Eigen::MatrixXd null_space;
null_space.setZero(this->flat_vertices.size() * 2, 3);
for (int i=0; i<this->flat_vertices.cols(); i++)
{
null_space(i * 2, 0) = 1; // x-translation
null_space(i * 2 + 1, 1) = 1; // y-translation
null_space(i * 2, 2) = - this->flat_vertices(1, i); // z-rotation
null_space(i * 2 + 1, 2) = this->flat_vertices(0, i); // z-rotation
}
return null_space;
}
}
// clang-format on