遵循这两个资源:
我用boost
写了一个Delaunay三角剖分。如果点坐标是积分的,它可以正常工作(我生成了几个随机测试,但没有观察到错误)。但是,如果这些点是非整数的,我会发现许多不正确的三角剖分,边缘缺失或边缘错误。
例如,此图像已使用舍入值构建并且是正确的(请参阅下面的代码)
但是这个图像是用原始值构建的并且不正确(参见下面的代码)
此代码重现了这两个示例(没有显示)。
#include <boost/polygon/voronoi.hpp>
using boost::polygon::voronoi_builder;
using boost::polygon::voronoi_diagram;
struct Point
{
double a;
double b;
Point(double x, double y) : a(x), b(y) {}
};
namespace boost
{
namespace polygon
{
template <>
struct geometry_concept<Point>
{
typedef point_concept type;
};
template <>
struct point_traits<Point>
{
typedef double coordinate_type;
static inline coordinate_type get(const Point& point, orientation_2d orient)
{
return (orient == HORIZONTAL) ? point.a : point.b;
}
};
} // polygon
} // boost
int main()
{
std::vector<double> xx = {8.45619987, 9.96573889, 0.26574428, 7.63918524, 8.15187618, 0.09100718};
std::vector<double> yy = {9.2452883, 7.0843455, 0.4811701, 3.1193826, 5.1336435, 5.5368374};
// std::vector<double> xx = {8, 10, 0, 8, 8, 0};
// std::vector<double> yy = {9, 7, 0, 3, 5, 6};
std::vector<Point> points;
for (int i = 0 ; i < xx.size() ; i++)
{
points.push_back(Point(xx[i], yy[i]));
}
// Construction of the Voronoi Diagram.
voronoi_diagram<double> vd;
construct_voronoi(points.begin(), points.end(), &vd);
for (const auto& vertex: vd.vertices())
{
std::vector<Point> triangle;
auto edge = vertex.incident_edge();
do
{
auto cell = edge->cell();
assert(cell->contains_point());
triangle.push_back(points[cell->source_index()]);
if (triangle.size() == 3)
{
// process output triangles
std::cout << "Got triangle: (" << triangle[0].a << " " << triangle[0].b << ") (" << triangle[1].a << " " << triangle[1].b << ") (" << triangle[2].a << " " << triangle[2].b << ")" << std::endl;
triangle.erase(triangle.begin() + 1);
}
edge = edge->rot_next();
} while (edge != vertex.incident_edge());
}
return 0;
}
如果点坐标不是十进制,它可以正常工作
在玩了你的样本后,我突然意识到你并不是说“当坐标不是十进制”时。你的意思是“积分”。很大的区别。
坐标类型应该是不可或缺的
和
所有算法都不支持浮点坐标类型,目前通常不适合与库一起使用。
我对你的输入数据看了很多。我只能从中“想象”出两个有效的多边形:
我们在代码中定义它们:
Ring const inputs[] = {
Ring { {0,0}, {8, 3}, {10, 7}, {8, 9}, {0, 6}, }, // {0, 0},
Ring { {0,0}, {8, 3}, {8, 5}, {10, 7}, {8, 9}, {0, 6}, } // {0, 0},
};
注释掉的结束点是因为您有一个需要关闭多边形的多边形模型。
在这种情况下,我选择了Boost Geometries多边形模型,并将其参数化为非闭合:
static constexpr bool closed_polygons = false; using bgPoly = bgm::polygon<Point, false, closed_polygons>; using bgMulti = bgm::multi_polygon<bgPoly>; using Ring = bgPoly::ring_type;
template <typename G> void validate(std::string name, G& geom) {
std::cout << name << ": " << bg::wkt(geom) << "\n";
std::string reason;
if (!bg::is_valid(geom, reason)) {
std::cout << name << ": " << reason << "\n";
bg::correct(geom);
std::cout << bg::wkt(geom) << "\n";
if (!bg::is_valid(geom, reason)) {
std::cout << name << " corrected: " << reason << "\n";
}
}
}
#include <boost/polygon/voronoi.hpp>
#include <cassert>
#include <iostream>
using boost::polygon::voronoi_builder;
using boost::polygon::voronoi_diagram;
struct Point
{
double a;
double b;
Point(double x = 0, double y = 0) : a(x), b(y) {}
};
namespace boost { namespace polygon {
template <> struct geometry_concept<Point> { typedef point_concept type; };
template <> struct point_traits<Point> {
typedef double coordinate_type;
static inline coordinate_type get(const Point& point, orientation_2d orient) {
return (orient == HORIZONTAL) ? point.a : point.b;
}
};
} }
#include <boost/geometry.hpp>
#include <boost/geometry/geometries/point_xy.hpp>
#include <boost/geometry/algorithms/convex_hull.hpp>
#include <boost/geometry/algorithms/transform.hpp>
#include <boost/geometry/strategies/transform.hpp>
#include <boost/geometry/geometries/polygon.hpp>
#include <boost/geometry/geometries/multi_polygon.hpp>
#include <boost/geometry/geometries/register/point.hpp>
#include <boost/geometry/io/io.hpp>
#include <fstream>
namespace bg = boost::geometry;
namespace bgm = bg::model;
namespace bgs = bg::strategy;
BOOST_GEOMETRY_REGISTER_POINT_2D(Point, double, bg::cs::cartesian, a, b)
static constexpr bool closed_polygons = false;
using bgPoly = bgm::polygon<Point, false, closed_polygons>;
using bgMulti = bgm::multi_polygon<bgPoly>;
using Ring = bgPoly::ring_type;
template <typename G> void validate(std::string name, G& geom) {
std::cout << name << ": " << bg::wkt(geom) << "\n";
std::string reason;
if (!bg::is_valid(geom, reason)) {
std::cout << name << ": " << reason << "\n";
bg::correct(geom);
std::cout << bg::wkt(geom) << "\n";
if (!bg::is_valid(geom, reason)) {
std::cout << name << " corrected: " << reason << "\n";
}
}
}
int main()
{
int count = 0;
Ring const inputs[] = {
Ring { {0,0}, {8, 3}, {10, 7}, {8, 9}, {0, 6}, }, // {0, 0},
Ring { {0,0}, {8, 3}, {8, 5}, {10, 7}, {8, 9}, {0, 6}, } // {0, 0},
};
bgs::transform::matrix_transformer<double, 2, 2> const transformations[] = {
{ 1, 0, 0, // identity transformation
0, 1, 0,
0, 0, 1 },
{ M_PI, 0, 1, // just to get nice non-integral numbers everywhere
0, M_PI, 1, // shift to (1,1) and scale everything by π
0, 0, 1 },
};
for (auto transformation : transformations) {
for (auto input : inputs) {
validate("Input", input);
Ring transformed_input;
bg::transform(input, transformed_input, transformation);
validate("transformed_input", transformed_input);
// Construction of the Voronoi Diagram.
voronoi_diagram<double> vd;
construct_voronoi(transformed_input.begin(), transformed_input.end(), &vd);
bgMulti out;
Ring triangle;
for (const auto& vertex: vd.vertices()) {
triangle.clear();
for(auto edge = vertex.incident_edge(); triangle.empty() || edge != vertex.incident_edge(); edge = edge->rot_next()) {
triangle.push_back(transformed_input[edge->cell()->source_index()]);
if (triangle.size() == 3) {
#if 0
std::cout << " -- found \n";
bgPoly t{triangle};
validate("Triangle", t);
out.push_back(t);
#else
out.push_back({ triangle });
#endif
triangle.erase(triangle.begin() + 1);
}
}
}
std::cout << "Out " << bg::wkt(out) << "\n";
{
std::ofstream svg("/tmp/svg" + std::to_string(++count) + ".svg");
boost::geometry::svg_mapper<Point> mapper(svg, 600, 600);
mapper.add(out);
mapper.map(out, R"(fill-opacity:0.5;fill:rgb(153,204,0);stroke:rgb(153,204,0);stroke-dasharray=5,5;stroke-width:2)");
mapper.add(transformed_input);
mapper.map(transformed_input, R"(fill-opacity:0.1;fill:rgb(204,153,0);stroke:red;stroke-width:3)");
}
} // inputs
} // transformations
}
输出:
Input: POLYGON((0 0,8 3,10 7,8 9,0 6))
transformed_input: POLYGON((0 0,8 3,10 7,8 9,0 6))
Out MULTIPOLYGON(((0 6,0 0,8 3,0 6)),((8 9,0 6,8 3,8 9)),((10 7,8 9,8 3,10 7)))
Input: POLYGON((0 0,8 3,8 5,10 7,8 9,0 6))
transformed_input: POLYGON((0 0,8 3,8 5,10 7,8 9,0 6))
Out MULTIPOLYGON(((0 6,0 0,8 3,0 6)),((8 5,0 6,8 3,8 5)),((8 9,0 6,8 5,8 9)),((8 9,8 5,10 7,8 9)),((10 7,8 5,8 3,10 7)))
Input: POLYGON((0 0,8 3,10 7,8 9,0 6))
transformed_input: POLYGON((1 1,26.1327 10.4248,32.4159 22.9911,26.1327 29.2743,1 19.8496))
Out MULTIPOLYGON(((1 19.8496,1 1,26.1327 10.4248,1 19.8496)),((26.1327 29.2743,1 19.8496,26.1327 10.4248,26.1327 29.2743)),((32.4159 22.9911,26.1327 29.2743,26.1327 10.4248,32.4159 22.9911)))
Input: POLYGON((0 0,8 3,8 5,10 7,8 9,0 6))
transformed_input: POLYGON((1 1,26.1327 10.4248,26.1327 16.708,32.4159 22.9911,26.1327 29.2743,1 19.8496))
Out MULTIPOLYGON(((1 19.8496,1 1,26.1327 10.4248,1 19.8496)),((26.1327 16.708,1 19.8496,26.1327 10.4248,26.1327 16.708)),((26.1327 29.2743,1 19.8496,26.1327 16.708,26.1327 29.2743)),((26.1327 29.2743,26.1327 16.708,32.4159 22.9911,26.1327 29.2743)),((32.4159 22.9911,26.1327 16.708,26.1327 10.4248,32.4159 22.9911)))
以及相应的SVG文件: