47 lines
1.1 KiB
C++
47 lines
1.1 KiB
C++
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#include "Geometry.hpp"
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#include <algorithm>
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namespace Slic3r {
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static bool
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sort_points (Point a, Point b)
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{
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return (a.x < b.x) || (a.x == b.x && a.y < b.y);
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}
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void
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convex_hull(Points points, Polygon &hull)
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{
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assert(points.size() >= 2);
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// sort input points
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std::sort(points.begin(), points.end(), sort_points);
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typedef const Point* PointPtr;
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PointPtr* out_hull = (PointPtr*)malloc(points.size()*2*sizeof(PointPtr));
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/* lower hull */
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size_t k = 0;
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for (Points::const_iterator it = points.begin(); it != points.end(); ++it) {
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while (k >= 2 && it->ccw(out_hull[k-2], out_hull[k-1]) <= 0) --k;
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Point pz = *&*it;
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out_hull[k++] = &*it;
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}
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/* upper hull */
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size_t t = k+1;
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for (Points::const_iterator it = points.end() - 2; it != points.begin(); --it) {
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while (k >= t && it->ccw(out_hull[k-2], out_hull[k-1]) <= 0) --k;
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out_hull[k++] = &*it;
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}
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// we assume hull is empty
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hull.points.reserve(k);
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for (size_t i = 0; i < k; ++i) {
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hull.points.push_back(*(out_hull[i]));
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}
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free(out_hull);
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}
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}
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