/// offset-ellipse Brent solver
/// offfset-ellipse solver using Brent's method
/// find the EllipsePosition that makes the offset-ellipse point be at p
/// this is a zero of Ellipse::error()
/// returns number of iterations
///
/// called (only?) by BullCutter::singleEdgeDropCanonical()
public int solver_brent()
{
int iters = 1;
EllipsePosition apos = new EllipsePosition(); // Brent's method requires bracketing the root in [apos.diangle, bpos.diangle]
EllipsePosition bpos = new EllipsePosition();
apos.setDiangle(0.0);
Debug.Assert(apos.isValid());
bpos.setDiangle(3.0);
Debug.Assert(bpos.isValid());
if (Math.Abs(error(apos)) < DefineConstants.OE_ERROR_TOLERANCE)
{ // if we are lucky apos is the solution
EllipsePosition1.CopyFrom(apos); // and we do not need to search further.
find_EllipsePosition2();
return(iters);
}
else if (Math.Abs(error(bpos)) < DefineConstants.OE_ERROR_TOLERANCE)
{ // or bpos might be the solution?
EllipsePosition1.CopyFrom(bpos);
find_EllipsePosition2();
return(iters);
}
// neither apos nor bpos is the solution
// but root is now bracketed, so we can use brent_zero
Debug.Assert(error(apos) * error(bpos) < 0.0);
// this looks for the diangle that makes the offset-ellipse point y-coordinate zero
double dia_sln = ocl.GlobalMembers.brent_zero(apos.diangle, bpos.diangle, 3E-16, DefineConstants.OE_ERROR_TOLERANCE, this); // brent_zero.hpp
EllipsePosition1.setDiangle(dia_sln);
Debug.Assert(EllipsePosition1.isValid());
// because we only work with the y-coordinate of the offset-ellipse-point, there are two symmetric solutions
find_EllipsePosition2();
return(iters);
}
/// return a normalized normal vector of the ellipse at the given EllipsePosition
//C++ TO C# CONVERTER WARNING: 'const' methods are not available in C#:
//ORIGINAL LINE: virtual Point normal(const EllipsePosition& pos) const
public virtual Point normal(EllipsePosition pos)
{
Debug.Assert(pos.isValid());
Point n = new Point(b * pos.s, a * pos.t, 0);
n.normalize();
return(new ocl.Point(n));
}