我需要一个算法来生成一个闭合的简单(无自相交)多边形曲线。它将成为我游戏中完美的迷宫。
请问您能否指导我正确的关键词?
请问您能否指导我正确的关键词?
你可能需要采用一些技巧来确保并集只是一个单一的形状。
rpoly.h
:#include <vector>
#include <list>
#include <algorithm>
#include <iterator>
#include <stdexcept>
#include <iostream>
using namespace std;
struct HalfEdge
{
HalfEdge() {};
HalfEdge(size_t start, size_t end) : start(start), end(end) {};
size_t start;
size_t end;
};
typedef vector<HalfEdge>::iterator edge_iterator;
typedef vector<HalfEdge>::const_iterator const_edge_iterator;
template <class Point>
struct non_intersecting_edges
{
non_intersecting_edges(const vector<Point>& vertices, vector<HalfEdge>& edgelist)
: vertices(vertices), edgelist(edgelist) {}
void operator() (size_t i)
{
const Point &p = vertices[i];
for (edge_iterator it=edgelist.begin(); it!=edgelist.end(); ++it)
{
HalfEdge edge = *it;
Point start_vertex = vertices[it->start];
Point end_vertex = vertices[it->end];
if (point_intersects_edge(p, start_vertex, end_vertex))
return; // skip this point
if(!edge_intersects_polygon(start_vertex, p) &&
!edge_intersects_polygon(end_vertex, p) )
{
edgelist.push_back( HalfEdge(i,it->end) );
it->end = i;
return;
}
}
cerr << "[rpoly] Warning: no possible edge found for vertex " << p << endl;
}
private:
bool point_intersects_edge(const Point& p, const Point& A, const Point& B) const
{
double d = (A.y-p.y) * (B.x-p.x) - (B.y-p.y) * (A.x-p.x);
if (abs(d) < 1e-14)
{
return ((A.x <= p.x && p.x <= B.x) || (A.x >= p.x && p.x >= B.x))
&& ((A.y <= p.y && p.y <= B.y) || (A.y >= p.y && p.y >= B.y));
}
else return false;
}
bool edge_intersects_polygon(const Point& A, const Point& B) const
{
double dx = B.x-A.x;
double dy = B.y-A.y;
for (const_edge_iterator it=edgelist.begin(); it!=edgelist.end(); ++it)
{
double d,u1,u2;
const Point &C = vertices[it->start];
const Point &D = vertices[it->end];
d = (D.y-C.y)*dx - (D.x-C.x)*dy;
if (d != 0) {
u1 = ((D.x-C.x)*(A.y-C.y) - (D.y-C.y)*(A.x-C.x)) / d;
u2 = (dx*(A.y-C.y) - dy*(A.x-C.x)) / d;
if (u1 > 0 && u1 <= 1 && u2 > 0 && u2 <= 1) // half-open edges
return true;
}
}
return false;
}
const vector<Point>& vertices;
vector<HalfEdge>& edgelist;
};
bool start_index_less(const HalfEdge &a, const HalfEdge &b)
{
return a.start < b.start;
}
bool start_index_equals(const HalfEdge &a, size_t idx)
{
return a.start == idx;
}
template <class Point>
struct random_point
{
Point operator () () const
{
return Point( rand() % 1000 - 500, rand() % 1000 - 500 );
}
};
const HalfEdge& find_edge(const vector<HalfEdge>& list, size_t start)
{
for (const_edge_iterator it=list.begin(); it!=list.end(); ++it)
if (it->start == start) return *it;
throw runtime_error("find_edge: requested edge not found");
}
/// \brief Outputs random, non self-intersecting polygon with \a N vertices
template <class Point, class OutputIterator>
void generate_random_polygon(unsigned int N, OutputIterator out)
{
if (N<3) return;
vector<Point> vertices(N);
generate(vertices.begin(), vertices.end(), random_point<Point>());
vector<HalfEdge> edgelist(2);
edgelist.reserve(N);
edgelist[0] = HalfEdge(0,1);
edgelist[1] = HalfEdge(1,0);
non_intersecting_edges<Point> generator(vertices,edgelist);
for (size_t i=2; i<vertices.size(); ++i)
generator(i);
int index=0;
for (unsigned int i=0; i<N; ++i)
{
const HalfEdge &edge = find_edge(edgelist, index);
*out++ = vertices[edge.start];
index = edge.end;
}
}
很抱歉我没有任何好的关键词给你查找。
我在想象一些由三角形在3D中逼近的3D地形。如果一个湖泊在轮廓线内形成,使得湖泊没有岛屿-那么湖泊的轮廓线就是您所需的多边形-并且它可能会对游戏产生相当直观的影响,因为它是基于真实世界的景观。
如果您能够找到众所周知的算法来制作由三角形组成的3D地形,我将找到最高点,并找到一个循环路径,使得循环中的最低点被最大化。根据地形的不同,您可能会得到一些有趣的多边形。
再次抱歉,我不知道任何完美的算法,但我认为这是一个非常有趣的问题。