Subversion Repositories planix.SVN

#include "mplot.h"
void parabola(double x0, double y0, double x1, double y1, double xb, double yb){
        register double x, y, t;
        double  c0x, c0y, c1x, c1y;
        double  dt, d2, d1;
        d1 = sqrt((xb - x0) * (xb - x0) + (yb - y0) * (yb - y0));
        d2 = sqrt((xb - x1) * (xb - x1) + (yb - y1) * (yb - y1));
        if (d1 <= e1->quantum || d2 <= e1->quantum) { 
                plotline(x0, y0, x1, y1); 
                return; 
        }
        c0x = x0 + x1 - 2. * xb; 
        c1x = 2. * (xb - x0);
        c0y = y0 + y1 - 2. * yb; 
        c1y = 2. * (yb - y0);
        move(x0, y0);
        dt = e1->quantum / d1;
        dt /= e1->grade;
        for (t = dt; t < 0.5; t += dt) {
                x = (c0x * t + c1x) * t + x0;
                y = (c0y * t + c1y) * t + y0;
                vec(x, y);
        }
        dt = e1->quantum / d2;
        dt /= e1->grade;
        for (; t < 1.0; t += dt) {
                x = (c0x * t + c1x) * t + x0;
                y = (c0y * t + c1y) * t + y0;
                vec(x, y);
        }
        vec(x1, y1);
}