private static void FindBounds(
out float outMin, out float outMax,
float start, float startLeaveTan, float startT,
float end, float endArriveTan, float endT,
bool curve)
{
outMin = FMath.Min(start, end);
outMax = FMath.Max(start, end);
// Do we need to consider extermeties of a curve?
if (curve)
{
// Scale tangents based on time interval, so this code matches the behaviour in FInterpCurve::Eval
float diff = endT - startT;
startLeaveTan *= diff;
endArriveTan *= diff;
float a = 6.0f * start + 3.0f * startLeaveTan + 3.0f * endArriveTan - 6.0f * end;
float b = -6.0f * start - 4.0f * startLeaveTan - 2.0f * endArriveTan + 6.0f * end;
float c = startLeaveTan;
float discriminant = (b * b) - (4.0f * a * c);
if (discriminant > 0.0f && !FMath.IsNearlyZero(a)) // Solving doesn't work if a is zero, which usually indicates co-incident start and end, and zero tangents anyway
{
float sqrtDisc = FMath.Sqrt(discriminant);
float x0 = (-b + sqrtDisc) / (2.0f * a); // x0 is the 'Alpha' ie between 0 and 1
float t0 = startT + x0 * (endT - startT); // Then t0 is the actual 'time' on the curve
if (t0 > startT && t0 < endT)
{
float val = FMath.CubicInterp(start, startLeaveTan, end, endArriveTan, x0);
outMin = FMath.Min(outMin, val);
outMax = FMath.Max(outMax, val);
}
float x1 = (-b - sqrtDisc) / (2.0f * a);
float t1 = startT + x1 * (endT - startT);
if (t1 > startT && t1 < endT)
{
float val = FMath.CubicInterp(start, startLeaveTan, end, endArriveTan, x1);
outMin = FMath.Min(outMin, val);
outMax = FMath.Max(outMax, val);
}
}
}
}
