private unsafe void IntersectionSearch(double *y, double *dydx, double hupper, KerrBlackHoleEquation equation)
{
double hlower = 0.0;
equation.Function(y, dydx);
while ((y[0] > equation.Rhor) && (y[0] < equation.R0 * 2))
{
double *yout = stackalloc double[equation.N];
double *yerr = stackalloc double[equation.N];
double hdiff = hupper - hlower;
if (Math.Abs(hdiff) < 1e-7)
{
RungeKutta.IntegrateStep(equation, y, dydx, hupper, yout, yerr);
Util.memcpy((IntPtr)y, (IntPtr)yout, equation.N * sizeof(double));
return;
}
double hmid = (hupper + hlower) / 2;
RungeKutta.IntegrateStep(equation, y, dydx, hmid, yout, yerr);
if (yout[0] < equation.R0)
{
hlower = hmid;
}
else
{
hupper = hmid;
}
}
}
/// <summary>
/// Use Runge-Kutta steps to find intersection with horizontal plane of the scene.
/// This is necessary to stop integrating when the ray hits the accretion disc.
/// </summary>
private unsafe void IntersectionSearch(double *y, double *dydx, double hupper, KerrBlackHoleEquation equation)
{
double hlower = 0.0;
int side;
if (y[1] > Math.PI / 2)
{
side = 1;
}
else if (y[1] < Math.PI / 2)
{
side = -1;
}
else
{
// unlikely, but needs to handle a situation when ray hits the plane EXACTLY
return;
}
equation.Function(y, dydx);
while ((y[0] > equation.Rhor) && (y[0] < equation.R0) && (side != 0))
{
double *yout = stackalloc double[equation.N];
double *yerr = stackalloc double[equation.N];
double hdiff = hupper - hlower;
if (Math.Abs(hdiff) < 1e-7)
{
RungeKutta.IntegrateStep(equation, y, dydx, hupper, yout, yerr);
Util.memcpy((IntPtr)y, (IntPtr)yout, equation.N * sizeof(double));
return;
}
double hmid = (hupper + hlower) / 2;
RungeKutta.IntegrateStep(equation, y, dydx, hmid, yout, yerr);
if (side * (yout[1] - Math.PI / 2) > 0)
{
hlower = hmid;
}
else
{
hupper = hmid;
}
}
}
protected unsafe void IntersectionSearch(double *y, double *dydx, double hupper, KerrBlackHoleEquation equation)
{
double hlower = 0.0;
double tempX = 0, tempY = 0, tempZ = 0;
equation.Function(y, dydx);
while ((y[0] > equation.Rhor) && (y[0] < equation.R0))
{
double *yout = stackalloc double[equation.N];
double *yerr = stackalloc double[equation.N];
double hdiff = hupper - hlower;
if (Math.Abs(hdiff) < 1e-7)
{
RungeKutta.IntegrateStep(equation, y, dydx, hupper, yout, yerr);
Util.memcpy((IntPtr)y, (IntPtr)yout, equation.N * sizeof(double));
return;
}
double hmid = (hupper + hlower) / 2;
RungeKutta.IntegrateStep(equation, y, dydx, hmid, yout, yerr);
Util.ToCartesian(yout[0], yout[1], yout[2], ref tempX, ref tempY, ref tempZ);
double distance = Math.Sqrt((tempX - centerX) * (tempX - centerX)
+ (tempY - centerY) * (tempY - centerY)
+ (tempZ - centerZ) * (tempZ - centerZ));
if (distance > radius)
{
hlower = hmid;
}
else
{
hupper = hmid;
}
}
}
