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pre cond 160

This commit is contained in:
Shlomo Golubev 2007-07-04 11:57:08 +00:00
parent 02140b0e17
commit cac2d4b037
1 changed files with 64 additions and 16 deletions
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80
Arrangement_2/include/CGAL/Arr_traits_2/Bezier_x_monotone_2.h
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@ -571,17 +571,17 @@ _Bezier_x_monotone_2<RatKer, AlgKer, NtTrt, BndTrt>::_Bezier_x_monotone_2
_is_vert (false)
{
// Get the originators of the point that correspond to the curve B.
Originator_iterator ps_org = ps.get_originator(B);
CGAL_precondition (ps_org != ps.originators_end());
Originator_iterator ps_org = ps.get_originator(B);
CGAL_precondition (ps_org != ps.originators_end());
Originator_iterator pt_org = pt.get_originator(B);
CGAL_precondition (pt_org != pt.originators_end());
// Check if the subcurve is directed left or right.
const Comparison_result res = _ps.compare_x (_pt, cache);
// Iddo: TODO - alternative check if the original curve is vertical,
// a check that can work on intervals.
if (res == EQUAL)
{
// We have a vertical segment. Check if the source is below the target.
@ -593,12 +593,12 @@ _Bezier_x_monotone_2<RatKer, AlgKer, NtTrt, BndTrt>::_Bezier_x_monotone_2
{
_dir_right = (res == SMALLER);
}
// Check if the value of the parameter t increases when we traverse the
// curve from left to right: If the curve is directed to the right, we
// check if t_src < t_trg, otherwise we check whether t_src > t_trg.
Comparison_result t_res;
if (CGAL::compare (ps_org->point_bound().t_max,
pt_org->point_bound().t_min) == SMALLER ||
CGAL::compare (ps_org->point_bound().t_min,
@ -1141,7 +1141,7 @@ _Bezier_x_monotone_2<RatKer, AlgKer, NtTrt, BndTrt>::compare_to_left
// Compare the slopes of the two supporting curves at p. In the general
// case, the slopes are not equal and their comparison gives us the
// vertical order to p's right; note that we swap the order of the curves
// to obtains their position to the left.
// to obtain their position to the left.
Comparison_result slope_res = cv._compare_slopes (*this, p);
if (slope_res != EQUAL)
@ -1259,7 +1259,9 @@ _Bezier_x_monotone_2<RatKer, AlgKer, NtTrt, BndTrt>::merge
(const Self& cv) const
{
CGAL_precondition (_curve.is_same (cv._curve));
Self res = cv;
if (right().is_same (cv.left()))
{
// Extend the subcurve to the right.
@ -1275,6 +1277,7 @@ _Bezier_x_monotone_2<RatKer, AlgKer, NtTrt, BndTrt>::merge
else
{
CGAL_precondition (left().is_same (cv.right()));
// Extend the subcurve to the left.
if (_dir_right)
{
@ -1285,6 +1288,7 @@ _Bezier_x_monotone_2<RatKer, AlgKer, NtTrt, BndTrt>::merge
res._pt = cv.left();
}
}
return (res);
}
@ -1504,26 +1508,70 @@ _Bezier_x_monotone_2<RatKer, AlgKer, NtTrt, BndTrt>::_compare_slopes
// The slope of (X(t), Y(t)) at t0 is Y'(t)/X'(t).
// Compute the slope of (*this).
// Note that we take special care of the case X'(t) = 0, when the tangent
// is vertical and its slope is +/- oo.
CGAL_assertion (org1->has_parameter() && org2->has_parameter());
Nt_traits nt_traits;
const Algebraic& t1 = org1->parameter();
Polynomial derivX = nt_traits.derive (_curve.x_polynomial());
Polynomial derivY = nt_traits.derive (_curve.y_polynomial());
Algebraic numer1 = nt_traits.evaluate_at (derivY, t1) *
nt_traits.convert (_curve.x_norm());
Algebraic denom1 = nt_traits.evaluate_at (derivX, t1) *
nt_traits.convert (_curve.y_norm());
CGAL::Sign inf_slope1 = CGAL::ZERO;
Algebraic slope1;
Algebraic slope1 = (nt_traits.evaluate_at (derivY, t1) *
nt_traits.convert (_curve.x_norm())) /
(nt_traits.evaluate_at (derivX, t1) *
nt_traits.convert (_curve.y_norm()));
if (CGAL::sign (denom1) == CGAL::ZERO)
{
inf_slope1 = CGAL::sign (numer1);
// If also Y'(t) = 0, we cannot perform the comparison:
if (inf_slope1 == CGAL::ZERO)
return (EQUAL);
}
else
{
slope1 = numer1 / denom1;
}
// Compute the slope of the other subcurve.
const Algebraic& t2 = org2->parameter();
derivX = nt_traits.derive (cv._curve.x_polynomial());
derivY = nt_traits.derive (cv._curve.y_polynomial());
Algebraic slope2 = (nt_traits.evaluate_at (derivY, t2) *
nt_traits.convert (cv._curve.x_norm())) /
(nt_traits.evaluate_at (derivX, t2) *
nt_traits.convert (cv._curve.y_norm()));
Algebraic numer2 = nt_traits.evaluate_at (derivY, t2) *
nt_traits.convert (cv._curve.x_norm());
Algebraic denom2 = nt_traits.evaluate_at (derivX, t2) *
nt_traits.convert (cv._curve.y_norm());
CGAL::Sign inf_slope2 = CGAL::ZERO;
Algebraic slope2;
if (CGAL::sign (denom2) == CGAL::ZERO)
{
inf_slope2 = CGAL::sign (numer2);
// If also Y'(t) = 0, we cannot perform the comparison:
if (inf_slope2 == CGAL::ZERO)
return (EQUAL);
}
else
{
slope2 = numer2 / denom2;
}
// Handle the comparison when one slope (or both) is +/- oo.
if (inf_slope1 == CGAL::POSITIVE)
return (inf_slope2 == CGAL::POSITIVE ? EQUAL : LARGER);
if (inf_slope1 == CGAL::NEGATIVE)
return (inf_slope2 == CGAL::NEGATIVE ? EQUAL : SMALLER);
if (inf_slope2 == CGAL::POSITIVE)
return (SMALLER);
if (inf_slope2 == CGAL::NEGATIVE)
return (LARGER);
// Compare the slopes.
return (CGAL::compare (slope1, slope2));