Imath::solveCubic returns wrong root

[hulud75]

Hi there,

I suspect Imath::solveCubic to return wrong results in some configurations.

This test does not pass on master (commit 8916ff5) :

    double roots[3];
    const double a = 36.1182938;
    const double b = -37.4285049;
    const double c = 0.0;
    const double d = 12.6194038;
    const int n = Imath::solveCubic(a, b, c, d, roots); // n is 1
    const double t = roots[0];
    double x = t*t*t*a + t*t*b + t*c + d;
    assert(std::fabs(x) < 0.000001);  // x is 6.8453819766985458

Best,

Cyril

[cary-ilm]

Closing, this should be resolved now.