84 lines
2.3 KiB
C++
84 lines
2.3 KiB
C++
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#include "fruchterman_reingold.hpp"
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#include "algebra.hpp"
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#include <algorithm>
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#include <cmath>
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#include <iostream>
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namespace nodesoup {
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using std::vector;
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FruchtermanReingold::FruchtermanReingold(const adj_list_t& g, double k)
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: g_(g)
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, k_(k)
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, k_squared_(k * k)
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, temp_(10 * sqrt(g.size()))
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, mvmts_(g_.size()) {}
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void FruchtermanReingold::operator()(vector<Point2D>& positions) {
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Vector2D zero = { 0.0, 0.0 };
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fill(mvmts_.begin(), mvmts_.end(), zero);
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// Repulsion force between vertice pairs
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for (vertex_id_t v_id = 0; v_id < g_.size(); v_id++) {
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for (vertex_id_t other_id = v_id + 1; other_id < g_.size(); other_id++) {
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if (v_id == other_id) {
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continue;
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}
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Vector2D delta = positions[v_id] - positions[other_id];
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double distance = delta.norm();
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// TODO: handle distance == 0.0
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// > 1000.0: not worth computing
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if (distance > 1000.0) {
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continue;
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}
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double repulsion = k_squared_ / distance;
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mvmts_[v_id] += delta / distance * repulsion;
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mvmts_[other_id] -= delta / distance * repulsion;
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}
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// Attraction force between edges
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for (vertex_id_t adj_id : g_[v_id]) {
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if (adj_id > v_id) {
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continue;
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}
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Vector2D delta = positions[v_id] - positions[adj_id];
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double distance = delta.norm();
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if (distance == 0.0) {
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continue;
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}
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double attraction = distance * distance / k_;
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mvmts_[v_id] -= delta / distance * attraction;
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mvmts_[adj_id] += delta / distance * attraction;
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}
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}
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// Max movement capped by current temperature
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for (vertex_id_t v_id = 0; v_id < g_.size(); v_id++) {
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double mvmt_norm = mvmts_[v_id].norm();
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// < 1.0: not worth computing
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if (mvmt_norm < 1.0) {
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continue;
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}
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double capped_mvmt_norm = std::min(mvmt_norm, temp_);
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Vector2D capped_mvmt = mvmts_[v_id] / mvmt_norm * capped_mvmt_norm;
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positions[v_id] += capped_mvmt;
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}
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// Cool down fast until we reach 1.5, then stay at low temperature
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if (temp_ > 1.5) {
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temp_ *= 0.85;
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} else {
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temp_ = 1.5;
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}
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}
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}
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