#include <iostream>
#include <ctime>
#include <GL/glut.h>
#include <math.h>
#include <vector>
using namespace std;
struct Pos
{
int x;
int y;
};
struct Edge
{
int x1, x2;
int y1, y2;
int vx;
int vy;
int a, b, c;
};
struct Poly
{
// 点集
int xx[100];
int yy[100];
// 边集
Edge Edges[100];
int plotNums = 0; //点数量
int edgeNums = 0; //边数量
// 记录凹点
int conv = 0;
};
Poly poly;
// 求交点坐标
Pos CrossPos(int p1,int p2){
Pos res;
int A1 = poly.Edges[p1].a;
int B1 = poly.Edges[p1].b;
int A2 = poly.Edges[p2].a;
int B2 = poly.Edges[p2].b;
int C1 = poly.Edges[p1].c;
int C2 = poly.Edges[p2].c;
int m = A1 * B2 - A2 * B1;
if (m == 0)
cout <<"第"<<p1<<"边和第"<<p2<<"边"<< "无交点" << endl;
else
{
res.x = (C2*B1 - C1 * B2) / m;
res.y = (C1*A2 - C2 * A1) / m;
}
return res;
}
// 判断点是否在线段内
bool JudgeInLine(Pos pos,Edge edge)
{
int maxX = edge.x1 >= edge.x2 ? edge.x1 : edge.x2;
int minX = edge.x1 <= edge.x2 ? edge.x1 : edge.x2;
int maxY = edge.y1 >= edge.y2 ? edge.y1 : edge.y2;
int minY = edge.y1 <= edge.y2 ? edge.y1 : edge.y2;
if (pos.x<=maxX && pos.x>=minX && pos.y<=maxY && pos.y>=minY)
{
return true;
}
return false;
}
// 求叉积 返回正负值
int CrossProduct(int n)
{
n = n % poly.edgeNums;
int np = (n + 1) % poly.edgeNums;
return (poly.Edges[n].vx*poly.Edges[np].vy - poly.Edges[np].vx*poly.Edges[n].vy) >= 0 ? 1 : -1;
}
// 切割凹多边形
void ChangePoly() {
int convP = poly.conv; //凹点的下一个点
Pos interPos;
for (int i = 0; i < poly.edgeNums; i++)
{
if (i<convP-1 || i>convP+1)
{
interPos = CrossPos(convP, i);
}
}
glClearColor(0.0, 0.0, 0.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT);
glBegin(GL_POLYGON);
glColor3f(1.0f, 0.0f, 0.0f);
for (int i = 0; i <= convP; i++)
{
glVertex2f(poly.xx[i], poly.yy[i]);
}
glVertex2f(interPos.x, interPos.y);
glEnd();
glBegin(GL_POLYGON);
glColor3f(0.0f, 1.0f, 1.0f);
glVertex2f(interPos.x, interPos.y);
for (int i=convP+1;i<poly.plotNums;i++)
{
glVertex2f(poly.xx[i], poly.yy[i]);
}
glEnd();
glFlush();
}
// 判断是什么多边形
bool Judge()
{
/*输出边信息*/
for (int i = 0; i < poly.edgeNums; i++)
{
cout << "Vx：" << poly.Edges[i].vx << " " << "Vy：" << poly.Edges[i].vy << " " << "A：" << poly.Edges[i].a<< " " << "B：" << poly.Edges[i].b << " " << "C：" << poly.Edges[i].c <<endl;
}
/*判断自交*/
Pos interPos;
if (poly.edgeNums > 3)
for (int i = 0; i < poly.edgeNums; i++)
{
interPos = CrossPos(i, (i + 2) % poly.edgeNums);
if (JudgeInLine(interPos, poly.Edges[i]) && JudgeInLine(interPos, poly.Edges[(i + 2) % poly.edgeNums]))
{
cout << "该多边形为自相交多边形" << endl;
return false;
}
}
/*判断凹凸*/
// 判断向量叉积 是否为同一正负
int judge;
if (CrossProduct(0) >= 0)
judge = 1;
else
judge = -1;
//判断每一个角，两边向量乘积是否同符号
for (int i = 1; i <= poly.edgeNums; i++)
{
if (judge*CrossProduct(i) < 0)
{
poly.conv = i;
ChangePoly();
cout << "该多边形为凹多边形" << endl;
return false;
}
}
cout << "该多边形为凸多边形" << endl;
return true;
}
void init(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glMatrixMode(GL_PROJECTION);//设置投影矩阵
gluOrtho2D(0.0, 400.0, 0.0, 300.0);//二维视景区域
glColor3f(1.0, 0.0, 0.0);
glPointSize(3.0);//点的大小
}
void plotpoint(GLint x, GLint y)
{
glBegin(GL_POINTS);
glVertex2i(x, y);
glEnd();
}
void displayFcn(void)
{
glClearColor(0.0, 0.0, 0.0, 0.0);
glClear(GL_COLOR_BUFFER_BIT);
for (int i = 0; i < poly.plotNums; i++)
{
plotpoint(poly.xx[i], poly.yy[i]);
}
glBegin(GL_POLYGON);
for (int i = 0; i < poly.edgeNums; i++)
{
glVertex2f(poly.xx[i], poly.yy[i]);
}
glEnd();
glFlush();
}
void mouse(GLint button, GLint action, GLint x, GLint y)
{
if (button == GLUT_LEFT_BUTTON && action == GLUT_DOWN)
{
poly.xx[poly.plotNums] = x;
poly.yy[poly.plotNums] = 300 - y;
cout << "x：" << x << " " << "y：" << 300 - y << endl;
poly.plotNums++;
glutPostRedisplay();//重绘窗口
}
if (button == GLUT_RIGHT_BUTTON && action == GLUT_DOWN)
{
poly.edgeNums = poly.plotNums;
if (poly.plotNums > 2)
{
for (int i = 1; i <= poly.plotNums; i++)
{
poly.Edges[i - 1].x1 = poly.xx[i - 1];
poly.Edges[i - 1].y1 = poly.yy[i - 1];
poly.Edges[i - 1].x2 = poly.xx[i%poly.plotNums];
poly.Edges[i - 1].y2 = poly.yy[i%poly.plotNums];
poly.Edges[i - 1].vx = poly.Edges[i - 1].x2 - poly.Edges[i - 1].x1;
poly.Edges[i - 1].vy = poly.Edges[i - 1].y2 - poly.Edges[i - 1].y1;
poly.Edges[i - 1].a = poly.Edges[i - 1].vy;
poly.Edges[i - 1].b = -poly.Edges[i - 1].vx;
poly.Edges[i - 1].c = poly.Edges[i - 1].x2 * poly.Edges[i - 1].y1 - poly.Edges[i - 1].x1 * poly.Edges[i - 1].y2;
}
if (Judge())
glutPostRedisplay();//重绘窗口
}
}
}
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
glutInitWindowPosition(50, 100);
glutInitWindowSize(400, 300);
glutCreateWindow("mouse");
init();
glutDisplayFunc(displayFcn);
glutMouseFunc(mouse);
glutMainLoop();
}
转载于:https://www.cnblogs.com/ruoh3kou/p/9893427.html
