101 lines
2.7 KiB
C++
101 lines
2.7 KiB
C++
// Begin License:
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// Copyright (C) 2006-2008 Tobias Sargeant (tobias.sargeant@gmail.com).
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// All rights reserved.
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//
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// This file is part of the Carve CSG Library (http://carve-csg.com/)
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//
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// This file may be used under the terms of the GNU General Public
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// License version 2.0 as published by the Free Software Foundation
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// and appearing in the file LICENSE.GPL2 included in the packaging of
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// this file.
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//
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// This file is provided "AS IS" with NO WARRANTY OF ANY KIND,
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// INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE.
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// End:
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#if defined(HAVE_CONFIG_H)
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# include <carve_config.h>
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#endif
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#include <carve/csg.hpp>
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#include <carve/convex_hull.hpp>
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#include <algorithm>
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namespace {
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bool grahamScan(const std::vector<carve::geom2d::P2> &points,
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int vpp, int vp,
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const std::vector<int> &ordered,
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int start,
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std::vector<int> &result, int _i = 0) {
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carve::geom2d::P2 v1 = points[vp] - points[vpp];
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if (start == (int)ordered.size()) return true;
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for (int i = start; i < (int)ordered.size(); ++i) {
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int v = ordered[i];
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carve::geom2d::P2 v2 = points[v] - points[vp];
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double cp = v1.x * v2.y - v2.x * v1.y;
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if (cp < 0) return false;
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int j = i + 1;
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while (j < (int)ordered.size() && points[ordered[j]] == points[v]) j++;
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result.push_back(v);
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if (grahamScan(points, vp, v, ordered, j, result, _i + 1)) return true;
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result.pop_back();
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}
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return false;
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}
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}
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namespace carve {
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namespace geom {
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std::vector<int> convexHull(const std::vector<carve::geom2d::P2> &points) {
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double max_x = points[0].x;
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unsigned max_v = 0;
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for (unsigned i = 1; i < points.size(); ++i) {
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if (points[i].x > max_x) {
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max_x = points[i].x;
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max_v = i;
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}
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}
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std::vector<std::pair<double, double> > angle_dist;
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std::vector<int> ordered;
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angle_dist.reserve(points.size());
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ordered.reserve(points.size() - 1);
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for (unsigned i = 0; i < points.size(); ++i) {
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if (i == max_v) continue;
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angle_dist[i] = std::make_pair(carve::math::ANG(carve::geom2d::atan2(points[i] - points[max_v])), distance2(points[i], points[max_v]));
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ordered.push_back(i);
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}
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std::sort(ordered.begin(),
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ordered.end(),
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make_index_sort(angle_dist.begin()));
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std::vector<int> result;
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result.push_back(max_v);
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result.push_back(ordered[0]);
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if (!grahamScan(points, max_v, ordered[0], ordered, 1, result)) {
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result.clear();
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throw carve::exception("convex hull failed!");
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}
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return result;
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}
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}
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}
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