parabola.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 }