分形Koch曲线实现及扩展：

注意事项：配置好OpenGL环境。

//Koch.h
#include <GL/glut.h>
#include <math.h>
#define PI 3.1415926
void Koch(float ax,float ay,float bx,float by, float c);
void DrawTrigon(float ax,float ay, float bx,float by,float cx,float cy,float c);

//Koch.cpp
#include"Koch.h"
//ax,ay,bx,by是直线端点坐标，c是最小分形线段长度
void Koch(float ax,float ay,float bx,float by, float c){
    if( (bx-ax)*(bx-ax) +(by-ay)*(by-ay) < c*c ){
        glBegin(GL_LINES);
        glVertex2f(ax,ay);
        glVertex2f(bx,by);
        glEnd();        
    }else {
        float dx,dy,ex,ey,fx,fy;
        dx = ax + (bx - ax)/3; 
        dy = ay + (by - ay)/3;
        fx = ax + (bx - ax)*2/3;
        fy = ay + (by - ay)*2/3;
        float l = sqrt( (fx - dx)*(fx - dx)+ (fy-dy)*(fy-dy) );
        //get the angle 
        double angle = atan( (fy - dy)/(fx - dx) );
        if( ( (angle>0&&(fx - dx) <0))||( (angle<0&&(fx - dx) <0)))angle += PI;
        ex = dx + cos(angle + PI/3)*l;
        ey = dy + sin(angle + PI/3)*l;
        Koch(ax,ay,dx,dy,c); 
        Koch(dx,dy,ex,ey,c);
        Koch(ex,ey,fx,fy,c);           
        Koch(fx,fy,bx,by,c);
    }
}
//ax,ay,bx,by,cx,cy是三角形顶点坐标，c是最小分形线段长度
void DrawTrigon(float ax,float ay, float bx,float by,float cx,float cy,float c){
    Koch(ax,ay,bx,by,c);
    Koch(bx,by,cx,cy,c);
    Koch(cx,cy,ax,ay,c);
}

//main.cpp
#include "Koch.h"
void display(){
    glClear(GL_COLOR_BUFFER_BIT);
    glColor3f(1.0,1.0,1.0);
  /* Koch(0.2,0.5 ,0.8,0.8,0.002);
     Koch(0.8,0.8, 0.5,0.2,0.002);
     Koch(0.5,0.2, 0.2,0.5,0.002);*/
    DrawTrigon(0.2,0.8,0.8,0.8,0.5,0.2,0.005);
    glFlush();
}
void init(){
    glClearColor(0.0,0.0,0.0,0.0);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0.0,1.0,0.0,1.0,-1.0,1.0);
}
int main(int argc, char * argv[]){
 glutInit(&argc,argv);
 glutInitWindowSize(800,800);
 glutInitWindowPosition(100,100);
 glutCreateWindow("Koch");
 init();
 glutDisplayFunc(display);
 glutMainLoop();
 return 0;
}