kotch curve opengl c++ code example

Example: kotch curve opengl c++

#include <GL/glut.h>
#include <math.h>
#include <list>
#include <iostream>
#define PI 3.14159/180

typedef struct _point {
  float x;
  float y;
}point;

using namespace std;

/* Deklaracije callback funkcija. */
static void on_display(void);

int main(int argc, char **argv)
{
    /* Inicijalizuje se GLUT. */
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_RGB | /*GLUT_DEPTH | */ GLUT_DOUBLE);

    /* Kreira se prozor. */
    glutInitWindowSize(800, 800);
    glutInitWindowPosition(100, 100);
    glutCreateWindow(argv[0]);
    glEnable (GL_LINE_SMOOTH);
    glEnable (GL_BLEND);
    glBlendFunc (GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glHint (GL_LINE_SMOOTH_HINT, GL_NICEST);


    /* Registruju se callback funkcije. */
    glutDisplayFunc(on_display);

    /* Obavlja se OpenGL inicijalizacija. */
    glClearColor(0.75, 0.75, 0.75, 0);
    glEnable(GL_DEPTH_TEST);

    /* Program ulazi u glavnu petlju. */
    glutMainLoop();

    return 0;
}

static void on_display(void)
{
    /* Brise se prethodni sadrzaj prozora. */
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
  
    list<point> l;
    list<point>::iterator i;
    point niz[3];
    point p1,p2;
    
    p1.x = -0.8;
    p1.y = 0;
    p2.x = 0.8;
    p2.y = 0;
    
    l.push_back(p1);
    l.push_back(p2);

    int br_iteracija = 4;

    while(br_iteracija > 0)
    {
        unsigned z = l.size();
        int p = 1;
        int j = 0;
        while(p < z)
        {
            if(j==0)
            {
              i = l.begin();
	      point pom1 = *i;
              i++;
	      point pom3 = *i;
              niz[0].x = ((pom3.x-pom1.x)/3) + pom1.x;
              niz[0].y = ((pom3.y-pom1.y)/3) + pom1.y;
	      niz[2].x = (2*((pom3.x-pom1.x))/3) + pom1.x;
	      niz[2].y = (2*((pom3.y-pom1.y))/3) + pom1.y;
	      
	      float r = sqrt(pow(niz[0].x-niz[2].x,2)+pow(niz[0].y-niz[2].y,2));
	      float altitude = (r*sqrt(3.0))/2;
	      float dx = niz[0].x - niz[2].x;
	      
	      point p;
	      p.x = ((pom3.x-pom1.x)/2) + pom1.x;
	      p.y = ((pom3.y-pom1.y)/2) + pom1.y;
	      
	      float slope = -dx / (niz[0].y-niz[2].y+0.000001);
	      
	      niz[1].x = sqrt(fabs(altitude*altitude - dx*dx)) / slope + p.x;
	      niz[1].y = slope * (niz[1].x - p.x) + p.y;
	      
              l.insert(i,niz,niz+3);
            }
            else
            {
                point pom1 = *i;
                i++;
		point pom3 = *i;
                niz[0].x = ((pom3.x-pom1.x)/3) + pom1.x;
		niz[0].y = ((pom3.y-pom1.y)/3) + pom1.y;
		niz[2].x = (2*((pom3.x-pom1.x))/3) + pom1.x;
		niz[2].y = (2*((pom3.y-pom1.y))/3) + pom1.y;
		
		float r = sqrt(pow(niz[0].x-niz[2].x,2)+pow(niz[0].y-niz[2].y,2));
		float altitude = (r*sqrt(3.0))/2;
		float dx = niz[0].x - niz[2].x;
		
		point p;
		p.x = ((pom3.x-pom1.x)/2) + pom1.x;
		p.y = ((pom3.y-pom1.y)/2) + pom1.y;
		
		float slope = -dx / (niz[0].y-niz[2].y+0.000001);
		
		niz[1].x = sqrt(fabs(altitude*altitude - dx*dx)) / slope + p.x;
		niz[1].y = slope * (niz[1].x - p.x) + p.y;
		
                l.insert(i,niz,niz+3);
            }
            p++;
            j++;
        }
        br_iteracija--;
    }

    glColor3f(0,0,1);
    //glPointSize(2);
    list<point>::iterator it;
    it = l.end();
    it--;
    
      for(i = l.begin();i!=it;i++) {
	glBegin(GL_LINES);
	point tmp = *i;
	i++;
	point tmp2 = *i;
	glVertex2f(tmp.x,tmp.y);
	glVertex2f(tmp2.x,tmp2.y);
	glEnd();
	i--;
      }

    /* Nova slika se salje na ekran. */
    glutSwapBuffers();
}