private void getMinMax(double p1, double p2, double p3, double p4, double[] minMax) {
if (p4 > p1) {
minMax[0] = p1;
minMax[1] = p4;
} else {
minMax[0] = p4;
minMax[1] = p1;
}
double c0 = 3 * (p2 - p1);
double c1 = 6 * (p3 - p2);
double c2 = 3 * (p4 - p3);
double[] eqn = {c0, c1 - 2 * c0, c2 - c1 + c0};
int roots = QuadCurve2D.solveQuadratic(eqn);
for (int r = 0; r < roots; r++) {
double tv = eqn[r];
if ((tv <= 0) || (tv >= 1)) continue;
tv =
((1 - tv) * (1 - tv) * (1 - tv) * p1
+ 3 * tv * (1 - tv) * (1 - tv) * p2
+ 3 * tv * tv * (1 - tv) * p3
+ tv * tv * tv * p4);
if (tv < minMax[0]) minMax[0] = tv;
else if (tv > minMax[1]) minMax[1] = tv;
}
}
