13e12c5d1SDavid du Colombier #include "mplot.h"
parabola(double x0,double y0,double x1,double y1,double xb,double yb)23e12c5d1SDavid du Colombier void parabola(double x0, double y0, double x1, double y1, double xb, double yb){
33e12c5d1SDavid du Colombier register double x, y, t;
43e12c5d1SDavid du Colombier double c0x, c0y, c1x, c1y;
53e12c5d1SDavid du Colombier double dt, d2, d1;
63e12c5d1SDavid du Colombier d1 = sqrt((xb - x0) * (xb - x0) + (yb - y0) * (yb - y0));
73e12c5d1SDavid du Colombier d2 = sqrt((xb - x1) * (xb - x1) + (yb - y1) * (yb - y1));
83e12c5d1SDavid du Colombier if (d1 <= e1->quantum || d2 <= e1->quantum) {
9*7dd7cddfSDavid du Colombier plotline(x0, y0, x1, y1);
103e12c5d1SDavid du Colombier return;
113e12c5d1SDavid du Colombier }
123e12c5d1SDavid du Colombier c0x = x0 + x1 - 2. * xb;
133e12c5d1SDavid du Colombier c1x = 2. * (xb - x0);
143e12c5d1SDavid du Colombier c0y = y0 + y1 - 2. * yb;
153e12c5d1SDavid du Colombier c1y = 2. * (yb - y0);
163e12c5d1SDavid du Colombier move(x0, y0);
173e12c5d1SDavid du Colombier dt = e1->quantum / d1;
183e12c5d1SDavid du Colombier dt /= e1->grade;
193e12c5d1SDavid du Colombier for (t = dt; t < 0.5; t += dt) {
203e12c5d1SDavid du Colombier x = (c0x * t + c1x) * t + x0;
213e12c5d1SDavid du Colombier y = (c0y * t + c1y) * t + y0;
223e12c5d1SDavid du Colombier vec(x, y);
233e12c5d1SDavid du Colombier }
243e12c5d1SDavid du Colombier dt = e1->quantum / d2;
253e12c5d1SDavid du Colombier dt /= e1->grade;
263e12c5d1SDavid du Colombier for (; t < 1.0; t += dt) {
273e12c5d1SDavid du Colombier x = (c0x * t + c1x) * t + x0;
283e12c5d1SDavid du Colombier y = (c0y * t + c1y) * t + y0;
293e12c5d1SDavid du Colombier vec(x, y);
303e12c5d1SDavid du Colombier }
313e12c5d1SDavid du Colombier vec(x1, y1);
323e12c5d1SDavid du Colombier }
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