tparabola.c - plan9port - [fork] Plan 9 from user space
  HTML git clone git://src.adamsgaard.dk/plan9port
   DIR Log
   DIR Files
   DIR Refs
   DIR README
   DIR LICENSE
       ---
       tparabola.c (815B)
       ---
            1 #include "mplot.h"
            2 void parabola(double x0, double y0, double x1, double y1, double xb, double yb){
            3         register double x, y, t;
            4         double        c0x, c0y, c1x, c1y;
            5         double        dt, d2, d1;
            6         d1 = sqrt((xb - x0) * (xb - x0) + (yb - y0) * (yb - y0));
            7         d2 = sqrt((xb - x1) * (xb - x1) + (yb - y1) * (yb - y1));
            8         if (d1 <= e1->quantum || d2 <= e1->quantum) {
            9                 plotline(x0, y0, x1, y1);
           10                 return;
           11         }
           12         c0x = x0 + x1 - 2. * xb;
           13         c1x = 2. * (xb - x0);
           14         c0y = y0 + y1 - 2. * yb;
           15         c1y = 2. * (yb - y0);
           16         move(x0, y0);
           17         dt = e1->quantum / d1;
           18         dt /= e1->grade;
           19         for (t = dt; t < 0.5; t += dt) {
           20                 x = (c0x * t + c1x) * t + x0;
           21                 y = (c0y * t + c1y) * t + y0;
           22                 vec(x, y);
           23         }
           24         dt = e1->quantum / d2;
           25         dt /= e1->grade;
           26         for (; t < 1.0; t += dt) {
           27                 x = (c0x * t + c1x) * t + x0;
           28                 y = (c0y * t + c1y) * t + y0;
           29                 vec(x, y);
           30         }
           31         vec(x1, y1);
           32 }