bezier-clipping.cpp revision 76addc201c409e81eaaa73fe27cc0f79c4db097c
/*
* Implement the Bezier clipping algorithm for finding
* Bezier curve intersection points and collinear normals
*
* Authors:
* Marco Cecchetti <mrcekets at gmail.com>
*
* Copyright 2008 authors
*
* This library is free software; you can redistribute it and/or
* modify it either under the terms of the GNU Lesser General Public
* License version 2.1 as published by the Free Software Foundation
* (the "LGPL") or, at your option, under the terms of the Mozilla
* Public License Version 1.1 (the "MPL"). If you do not alter this
* notice, a recipient may use your version of this file under either
* the MPL or the LGPL.
*
* You should have received a copy of the LGPL along with this library
* in the file COPYING-LGPL-2.1; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
* You should have received a copy of the MPL along with this library
* in the file COPYING-MPL-1.1
*
* The contents of this file are subject to the Mozilla Public License
* Version 1.1 (the "License"); you may not use this file except in
* compliance with the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
* OF ANY KIND, either express or implied. See the LGPL or the MPL for
* the specific language governing rights and limitations.
*/
#include <2geom/basic-intersection.h>
#include <2geom/choose.h>
#include <2geom/point.h>
#include <2geom/interval.h>
#include <2geom/bezier.h>
#include <2geom/numeric/matrix.h>
#include <2geom/convex-hull.h>
#include <2geom/line.h>
#include <cassert>
#include <vector>
#include <algorithm>
#include <utility>
//#include <iomanip>
using std::swap;
#define VERBOSE 0
#define CHECK 0
namespace Geom {
namespace detail { namespace bezier_clipping {
////////////////////////////////////////////////////////////////////////////////
// for debugging
//
void print(std::vector<Point> const& cp, const char* msg = "")
{
std::cerr << msg << std::endl;
for (size_t i = 0; i < cp.size(); ++i)
std::cerr << i << " : " << cp[i] << std::endl;
}
template< class charT >
std::basic_ostream<charT> &
operator<< (std::basic_ostream<charT> & os, const Interval & I)
{
os << "[" << I.min() << ", " << I.max() << "]";
return os;
}
double angle (std::vector<Point> const& A)
{
size_t n = A.size() -1;
double a = std::atan2(A[n][Y] - A[0][Y], A[n][X] - A[0][X]);
return (180 * a / M_PI);
}
size_t get_precision(Interval const& I)
{
double d = I.extent();
double e = 0.1, p = 10;
int n = 0;
while (n < 16 && d < e)
{
p *= 10;
e = 1/p;
++n;
}
return n;
}
void range_assertion(int k, int m, int n, const char* msg)
{
if ( k < m || k > n)
{
std::cerr << "range assertion failed: \n"
<< msg << std::endl
<< "value: " << k
<< " range: " << m << ", " << n << std::endl;
assert (k >= m && k <= n);
}
}
////////////////////////////////////////////////////////////////////////////////
// numerical routines
/*
* Compute the binomial coefficient (n, k)
*/
double binomial(unsigned int n, unsigned int k)
{
return choose<double>(n, k);
}
/*
* Compute the determinant of the 2x2 matrix with column the point P1, P2
*/
double det(Point const& P1, Point const& P2)
{
return P1[X]*P2[Y] - P1[Y]*P2[X];
}
/*
* Solve the linear system [P1,P2] * P = Q
* in case there isn't exactly one solution the routine returns false
*/
bool solve(Point & P, Point const& P1, Point const& P2, Point const& Q)
{
double d = det(P1, P2);
if (d == 0) return false;
d = 1 / d;
P[X] = det(Q, P2) * d;
P[Y] = det(P1, Q) * d;
return true;
}
////////////////////////////////////////////////////////////////////////////////
// interval routines
/*
* Map the sub-interval I in [0,1] into the interval J and assign it to J
*/
void map_to(Interval & J, Interval const& I)
{
J.setEnds(J.valueAt(I.min()), J.valueAt(I.max()));
}
////////////////////////////////////////////////////////////////////////////////
// bezier curve routines
/*
* Return true if all the Bezier curve control points are near,
* false otherwise
*/
// Bezier.isConstant(precision)
bool is_constant(std::vector<Point> const& A, double precision)
{
for (unsigned int i = 1; i < A.size(); ++i)
{
if(!are_near(A[i], A[0], precision))
return false;
}
return true;
}
/*
* Compute the hodograph of the bezier curve B and return it in D
*/
// derivative(Bezier)
void derivative(std::vector<Point> & D, std::vector<Point> const& B)
{
D.clear();
size_t sz = B.size();
if (sz == 0) return;
if (sz == 1)
{
D.resize(1, Point(0,0));
return;
}
size_t n = sz-1;
D.reserve(n);
for (size_t i = 0; i < n; ++i)
{
D.push_back(n*(B[i+1] - B[i]));
}
}
/*
* Compute the hodograph of the Bezier curve B rotated of 90 degree
* and return it in D; we have N(t) orthogonal to B(t) for any t
*/
// rot90(derivative(Bezier))
void normal(std::vector<Point> & N, std::vector<Point> const& B)
{
derivative(N,B);
for (size_t i = 0; i < N.size(); ++i)
{
N[i] = rot90(N[i]);
}
}
/*
* Compute the portion of the Bezier curve "B" wrt the interval [0,t]
*/
// portion(Bezier, 0, t)
void left_portion(Coord t, std::vector<Point> & B)
{
size_t n = B.size();
for (size_t i = 1; i < n; ++i)
{
for (size_t j = n-1; j > i-1 ; --j)
{
B[j] = lerp(t, B[j-1], B[j]);
}
}
}
/*
* Compute the portion of the Bezier curve "B" wrt the interval [t,1]
*/
// portion(Bezier, t, 1)
void right_portion(Coord t, std::vector<Point> & B)
{
size_t n = B.size();
for (size_t i = 1; i < n; ++i)
{
for (size_t j = 0; j < n-i; ++j)
{
B[j] = lerp(t, B[j], B[j+1]);
}
}
}
/*
* Compute the portion of the Bezier curve "B" wrt the interval "I"
*/
// portion(Bezier, I)
void portion (std::vector<Point> & B , Interval const& I)
{
if (I.min() == 0)
{
if (I.max() == 1) return;
left_portion(I.max(), B);
return;
}
right_portion(I.min(), B);
if (I.max() == 1) return;
double t = I.extent() / (1 - I.min());
left_portion(t, B);
}
////////////////////////////////////////////////////////////////////////////////
// tags
struct intersection_point_tag;
struct collinear_normal_tag;
template <typename Tag>
OptInterval clip(std::vector<Point> const& A,
std::vector<Point> const& B,
double precision);
template <typename Tag>
void iterate(std::vector<Interval>& domsA,
std::vector<Interval>& domsB,
std::vector<Point> const& A,
std::vector<Point> const& B,
Interval const& domA,
Interval const& domB,
double precision );
////////////////////////////////////////////////////////////////////////////////
// intersection
/*
* Make up an orientation line using the control points c[i] and c[j]
* the line is returned in the output parameter "l" in the form of a 3 element
* vector : l[0] * x + l[1] * y + l[2] == 0; the line is normalized.
*/
// Line(c[i], c[j])
void orientation_line (std::vector<double> & l,
std::vector<Point> const& c,
size_t i, size_t j)
{
l[0] = c[j][Y] - c[i][Y];
l[1] = c[i][X] - c[j][X];
l[2] = cross(c[j], c[i]);
double length = std::sqrt(l[0] * l[0] + l[1] * l[1]);
assert (length != 0);
l[0] /= length;
l[1] /= length;
l[2] /= length;
}
/*
* Pick up an orientation line for the Bezier curve "c" and return it in
* the output parameter "l"
*/
Line pick_orientation_line (std::vector<Point> const &c, double precision)
{
size_t i = c.size();
while (--i > 0 && are_near(c[0], c[i], precision))
{}
// this should never happen because when a new curve portion is created
// we check that it is not constant;
// however this requires that the precision used in the is_constant
// routine has to be the same used here in the are_near test
assert(i != 0);
Line line(c[0], c[i]);
return line;
//std::cerr << "i = " << i << std::endl;
}
/*
* Make up an orientation line for constant bezier curve;
* the orientation line is made up orthogonal to the other curve base line;
* the line is returned in the output parameter "l" in the form of a 3 element
* vector : l[0] * x + l[1] * y + l[2] == 0; the line is normalized.
*/
Line orthogonal_orientation_line (std::vector<Point> const &c,
Point const &p,
double precision)
{
// this should never happen
assert(!is_constant(c, precision));
Line line(p, (c.back() - c.front()).cw() + p);
return line;
}
/*
* Compute the signed distance of the point "P" from the normalized line l
*/
double signed_distance(Point const &p, Line const &l)
{
Coord a, b, c;
l.coefficients(a, b, c);
return a * p[X] + b * p[Y] + c;
}
/*
* Compute the min and max distance of the control points of the Bezier
* curve "c" from the normalized orientation line "l".
* This bounds are returned through the output Interval parameter"bound".
*/
Interval fat_line_bounds (std::vector<Point> const &c,
Line const &l)
{
Interval bound(0, 0);
for (size_t i = 0; i < c.size(); ++i) {
bound.expandTo(signed_distance(c[i], l));
}
return bound;
}
/*
* return the x component of the intersection point between the line
* passing through points p1, p2 and the line Y = "y"
*/
double intersect (Point const& p1, Point const& p2, double y)
{
// we are sure that p2[Y] != p1[Y] because this routine is called
// only when the lower or the upper bound is crossed
double dy = (p2[Y] - p1[Y]);
double s = (y - p1[Y]) / dy;
return (p2[X]-p1[X])*s + p1[X];
}
/*
* Clip the Bezier curve "B" wrt the fat line defined by the orientation
* line "l" and the interval range "bound", the new parameter interval for
* the clipped curve is returned through the output parameter "dom"
*/
OptInterval clip_interval (std::vector<Point> const& B,
Line const &l,
Interval const &bound)
{
double n = B.size() - 1; // number of sub-intervals
std::vector<Point> D; // distance curve control points
D.reserve (B.size());
for (size_t i = 0; i < B.size(); ++i)
{
const double d = signed_distance(B[i], l);
D.push_back (Point(i/n, d));
}
//print(D);
ConvexHull p;
p.swap(D);
//print(p);
bool plower, phigher;
bool clower, chigher;
double t, tmin = 1, tmax = 0;
// std::cerr << "bound : " << bound << std::endl;
plower = (p[0][Y] < bound.min());
phigher = (p[0][Y] > bound.max());
if (!(plower || phigher)) // inside the fat line
{
if (tmin > p[0][X]) tmin = p[0][X];
if (tmax < p[0][X]) tmax = p[0][X];
// std::cerr << "0 : inside " << p[0]
// << " : tmin = " << tmin << ", tmax = " << tmax << std::endl;
}
for (size_t i = 1; i < p.size(); ++i)
{
clower = (p[i][Y] < bound.min());
chigher = (p[i][Y] > bound.max());
if (!(clower || chigher)) // inside the fat line
{
if (tmin > p[i][X]) tmin = p[i][X];
if (tmax < p[i][X]) tmax = p[i][X];
// std::cerr << i << " : inside " << p[i]
// << " : tmin = " << tmin << ", tmax = " << tmax
// << std::endl;
}
if (clower != plower) // cross the lower bound
{
t = intersect(p[i-1], p[i], bound.min());
if (tmin > t) tmin = t;
if (tmax < t) tmax = t;
plower = clower;
// std::cerr << i << " : lower " << p[i]
// << " : tmin = " << tmin << ", tmax = " << tmax
// << std::endl;
}
if (chigher != phigher) // cross the upper bound
{
t = intersect(p[i-1], p[i], bound.max());
if (tmin > t) tmin = t;
if (tmax < t) tmax = t;
phigher = chigher;
// std::cerr << i << " : higher " << p[i]
// << " : tmin = " << tmin << ", tmax = " << tmax
// << std::endl;
}
}
// we have to test the closing segment for intersection
size_t last = p.size() - 1;
clower = (p[0][Y] < bound.min());
chigher = (p[0][Y] > bound.max());
if (clower != plower) // cross the lower bound
{
t = intersect(p[last], p[0], bound.min());
if (tmin > t) tmin = t;
if (tmax < t) tmax = t;
// std::cerr << "0 : lower " << p[0]
// << " : tmin = " << tmin << ", tmax = " << tmax << std::endl;
}
if (chigher != phigher) // cross the upper bound
{
t = intersect(p[last], p[0], bound.max());
if (tmin > t) tmin = t;
if (tmax < t) tmax = t;
// std::cerr << "0 : higher " << p[0]
// << " : tmin = " << tmin << ", tmax = " << tmax << std::endl;
}
if (tmin == 1 && tmax == 0) {
return OptInterval();
} else {
return Interval(tmin, tmax);
}
}
/*
* Clip the Bezier curve "B" wrt the Bezier curve "A" for individuating
* intersection points the new parameter interval for the clipped curve
* is returned through the output parameter "dom"
*/
template <>
OptInterval clip<intersection_point_tag> (std::vector<Point> const& A,
std::vector<Point> const& B,
double precision)
{
Line bl;
if (is_constant(A, precision)) {
Point M = middle_point(A.front(), A.back());
bl = orthogonal_orientation_line(B, M, precision);
} else {
bl = pick_orientation_line(A, precision);
}
bl.normalize();
Interval bound = fat_line_bounds(A, bl);
return clip_interval(B, bl, bound);
}
///////////////////////////////////////////////////////////////////////////////
// collinear normal
/*
* Compute a closed focus for the Bezier curve B and return it in F
* A focus is any curve through which all lines perpendicular to B(t) pass.
*/
void make_focus (std::vector<Point> & F, std::vector<Point> const& B)
{
assert (B.size() > 2);
size_t n = B.size() - 1;
normal(F, B);
Point c(1, 1);
#if VERBOSE
if (!solve(c, F[0], -F[n-1], B[n]-B[0]))
{
std::cerr << "make_focus: unable to make up a closed focus" << std::endl;
}
#else
solve(c, F[0], -F[n-1], B[n]-B[0]);
#endif
// std::cerr << "c = " << c << std::endl;
// B(t) + c(t) * N(t)
double n_inv = 1 / (double)(n);
Point c0ni;
F.push_back(c[1] * F[n-1]);
F[n] += B[n];
for (size_t i = n-1; i > 0; --i)
{
F[i] *= -c[0];
c0ni = F[i];
F[i] += (c[1] * F[i-1]);
F[i] *= (i * n_inv);
F[i] -= c0ni;
F[i] += B[i];
}
F[0] *= c[0];
F[0] += B[0];
}
/*
* Compute the projection on the plane (t, d) of the control points
* (t, u, D(t,u)) where D(t,u) = <(B(t) - F(u)), B'(t)> with 0 <= t, u <= 1
* B is a Bezier curve and F is a focus of another Bezier curve.
* See Sederberg, Nishita, 1990 - Curve intersection using Bezier clipping.
*/
void distance_control_points (std::vector<Point> & D,
std::vector<Point> const& B,
std::vector<Point> const& F)
{
assert (B.size() > 1);
assert (!F.empty());
const size_t n = B.size() - 1;
const size_t m = F.size() - 1;
const size_t r = 2 * n - 1;
const double r_inv = 1 / (double)(r);
D.clear();
D.reserve (B.size() * F.size());
std::vector<Point> dB;
dB.reserve(n);
for (size_t k = 0; k < n; ++k)
{
dB.push_back (B[k+1] - B[k]);
}
NL::Matrix dBB(n,B.size());
for (size_t i = 0; i < n; ++i)
for (size_t j = 0; j < B.size(); ++j)
dBB(i,j) = dot (dB[i], B[j]);
NL::Matrix dBF(n, F.size());
for (size_t i = 0; i < n; ++i)
for (size_t j = 0; j < F.size(); ++j)
dBF(i,j) = dot (dB[i], F[j]);
size_t l;
double bc;
Point dij;
std::vector<double> d(F.size());
for (size_t i = 0; i <= r; ++i)
{
for (size_t j = 0; j <= m; ++j)
{
d[j] = 0;
}
const size_t k0 = std::max(i, n) - n;
const size_t kn = std::min(i, n-1);
const double bri = n / binomial(r,i);
for (size_t k = k0; k <= kn; ++k)
{
//if (k > i || (i-k) > n) continue;
l = i - k;
#if CHECK
assert (l <= n);
#endif
bc = bri * binomial(n,l) * binomial(n-1, k);
for (size_t j = 0; j <= m; ++j)
{
//d[j] += bc * dot(dB[k], B[l] - F[j]);
d[j] += bc * (dBB(k,l) - dBF(k,j));
}
}
double dmin, dmax;
dmin = dmax = d[m];
for (size_t j = 0; j < m; ++j)
{
if (dmin > d[j]) dmin = d[j];
if (dmax < d[j]) dmax = d[j];
}
dij[0] = i * r_inv;
dij[1] = dmin;
D.push_back (dij);
dij[1] = dmax;
D.push_back (dij);
}
}
/*
* Clip the Bezier curve "B" wrt the focus "F"; the new parameter interval for
* the clipped curve is returned through the output parameter "dom"
*/
OptInterval clip_interval (std::vector<Point> const& B,
std::vector<Point> const& F)
{
std::vector<Point> D; // distance curve control points
distance_control_points(D, B, F);
//print(D, "D");
// ConvexHull chD(D);
// std::vector<Point>& p = chD.boundary; // convex hull vertices
ConvexHull p;
p.swap(D);
//print(p, "CH(D)");
bool plower, clower;
double t, tmin = 1, tmax = 0;
plower = (p[0][Y] < 0);
if (p[0][Y] == 0) // on the x axis
{
if (tmin > p[0][X]) tmin = p[0][X];
if (tmax < p[0][X]) tmax = p[0][X];
// std::cerr << "0 : on x axis " << p[0]
// << " : tmin = " << tmin << ", tmax = " << tmax << std::endl;
}
for (size_t i = 1; i < p.size(); ++i)
{
clower = (p[i][Y] < 0);
if (p[i][Y] == 0) // on x axis
{
if (tmin > p[i][X]) tmin = p[i][X];
if (tmax < p[i][X]) tmax = p[i][X];
// std::cerr << i << " : on x axis " << p[i]
// << " : tmin = " << tmin << ", tmax = " << tmax
// << std::endl;
}
else if (clower != plower) // cross the x axis
{
t = intersect(p[i-1], p[i], 0);
if (tmin > t) tmin = t;
if (tmax < t) tmax = t;
plower = clower;
// std::cerr << i << " : lower " << p[i]
// << " : tmin = " << tmin << ", tmax = " << tmax
// << std::endl;
}
}
// we have to test the closing segment for intersection
size_t last = p.size() - 1;
clower = (p[0][Y] < 0);
if (clower != plower) // cross the x axis
{
t = intersect(p[last], p[0], 0);
if (tmin > t) tmin = t;
if (tmax < t) tmax = t;
// std::cerr << "0 : lower " << p[0]
// << " : tmin = " << tmin << ", tmax = " << tmax << std::endl;
}
if (tmin == 1 && tmax == 0) {
return OptInterval();
} else {
return Interval(tmin, tmax);
}
}
/*
* Clip the Bezier curve "B" wrt the Bezier curve "A" for individuating
* points which have collinear normals; the new parameter interval
* for the clipped curve is returned through the output parameter "dom"
*/
template <>
OptInterval clip<collinear_normal_tag> (std::vector<Point> const& A,
std::vector<Point> const& B,
double /*precision*/)
{
std::vector<Point> F;
make_focus(F, A);
return clip_interval(B, F);
}
const double MAX_PRECISION = 1e-8;
const double MIN_CLIPPED_SIZE_THRESHOLD = 0.8;
const Interval UNIT_INTERVAL(0,1);
const OptInterval EMPTY_INTERVAL;
const Interval H1_INTERVAL(0, 0.5);
const Interval H2_INTERVAL(nextafter(0.5, 1.0), 1.0);
/*
* iterate
*
* input:
* A, B: control point sets of two bezier curves
* domA, domB: real parameter intervals of the two curves
* precision: required computational precision of the returned parameter ranges
* output:
* domsA, domsB: sets of parameter intervals
*
* The parameter intervals are computed by using a Bezier clipping algorithm,
* in case the clipping doesn't shrink the initial interval more than 20%,
* a subdivision step is performed.
* If during the computation both curves collapse to a single point
* the routine exits indipendently by the precision reached in the computation
* of the curve intervals.
*/
template <>
void iterate<intersection_point_tag> (std::vector<Interval>& domsA,
std::vector<Interval>& domsB,
std::vector<Point> const& A,
std::vector<Point> const& B,
Interval const& domA,
Interval const& domB,
double precision )
{
// in order to limit recursion
static size_t counter = 0;
if (domA.extent() == 1 && domB.extent() == 1) counter = 0;
if (++counter > 100) return;
#if VERBOSE
std::cerr << std::fixed << std::setprecision(16);
std::cerr << ">> curve subdision performed <<" << std::endl;
std::cerr << "dom(A) : " << domA << std::endl;
std::cerr << "dom(B) : " << domB << std::endl;
// std::cerr << "angle(A) : " << angle(A) << std::endl;
// std::cerr << "angle(B) : " << angle(B) << std::endl;
#endif
if (precision < MAX_PRECISION)
precision = MAX_PRECISION;
std::vector<Point> pA = A;
std::vector<Point> pB = B;
std::vector<Point>* C1 = &pA;
std::vector<Point>* C2 = &pB;
Interval dompA = domA;
Interval dompB = domB;
Interval* dom1 = &dompA;
Interval* dom2 = &dompB;
OptInterval dom;
if ( is_constant(A, precision) && is_constant(B, precision) ){
Point M1 = middle_point(C1->front(), C1->back());
Point M2 = middle_point(C2->front(), C2->back());
if (are_near(M1,M2)){
domsA.push_back(domA);
domsB.push_back(domB);
}
return;
}
size_t iter = 0;
while (++iter < 100
&& (dompA.extent() >= precision || dompB.extent() >= precision))
{
#if VERBOSE
std::cerr << "iter: " << iter << std::endl;
#endif
dom = clip<intersection_point_tag>(*C1, *C2, precision);
if (dom.isEmpty())
{
#if VERBOSE
std::cerr << "dom: empty" << std::endl;
#endif
return;
}
#if VERBOSE
std::cerr << "dom : " << dom << std::endl;
#endif
// all other cases where dom[0] > dom[1] are invalid
assert(dom->min() <= dom->max());
map_to(*dom2, *dom);
portion(*C2, *dom);
if (is_constant(*C2, precision) && is_constant(*C1, precision))
{
Point M1 = middle_point(C1->front(), C1->back());
Point M2 = middle_point(C2->front(), C2->back());
#if VERBOSE
std::cerr << "both curves are constant: \n"
<< "M1: " << M1 << "\n"
<< "M2: " << M2 << std::endl;
print(*C2, "C2");
print(*C1, "C1");
#endif
if (are_near(M1,M2))
break; // append the new interval
else
return; // exit without appending any new interval
}
// if we have clipped less than 20% than we need to subdive the curve
// with the largest domain into two sub-curves
if (dom->extent() > MIN_CLIPPED_SIZE_THRESHOLD)
{
#if VERBOSE
std::cerr << "clipped less than 20% : " << dom->extent() << std::endl;
std::cerr << "angle(pA) : " << angle(pA) << std::endl;
std::cerr << "angle(pB) : " << angle(pB) << std::endl;
#endif
std::vector<Point> pC1, pC2;
Interval dompC1, dompC2;
if (dompA.extent() > dompB.extent())
{
pC1 = pC2 = pA;
portion(pC1, H1_INTERVAL);
portion(pC2, H2_INTERVAL);
dompC1 = dompC2 = dompA;
map_to(dompC1, H1_INTERVAL);
map_to(dompC2, H2_INTERVAL);
iterate<intersection_point_tag>(domsA, domsB, pC1, pB,
dompC1, dompB, precision);
iterate<intersection_point_tag>(domsA, domsB, pC2, pB,
dompC2, dompB, precision);
}
else
{
pC1 = pC2 = pB;
portion(pC1, H1_INTERVAL);
portion(pC2, H2_INTERVAL);
dompC1 = dompC2 = dompB;
map_to(dompC1, H1_INTERVAL);
map_to(dompC2, H2_INTERVAL);
iterate<intersection_point_tag>(domsB, domsA, pC1, pA,
dompC1, dompA, precision);
iterate<intersection_point_tag>(domsB, domsA, pC2, pA,
dompC2, dompA, precision);
}
return;
}
swap(C1, C2);
swap(dom1, dom2);
#if VERBOSE
std::cerr << "dom(pA) : " << dompA << std::endl;
std::cerr << "dom(pB) : " << dompB << std::endl;
#endif
}
domsA.push_back(dompA);
domsB.push_back(dompB);
}
/*
* iterate
*
* input:
* A, B: control point sets of two bezier curves
* domA, domB: real parameter intervals of the two curves
* precision: required computational precision of the returned parameter ranges
* output:
* domsA, domsB: sets of parameter intervals
*
* The parameter intervals are computed by using a Bezier clipping algorithm,
* in case the clipping doesn't shrink the initial interval more than 20%,
* a subdivision step is performed.
* If during the computation one of the two curve interval length becomes less
* than MAX_PRECISION the routine exits indipendently by the precision reached
* in the computation of the other curve interval.
*/
template <>
void iterate<collinear_normal_tag> (std::vector<Interval>& domsA,
std::vector<Interval>& domsB,
std::vector<Point> const& A,
std::vector<Point> const& B,
Interval const& domA,
Interval const& domB,
double precision)
{
// in order to limit recursion
static size_t counter = 0;
if (domA.extent() == 1 && domB.extent() == 1) counter = 0;
if (++counter > 100) return;
#if VERBOSE
std::cerr << std::fixed << std::setprecision(16);
std::cerr << ">> curve subdision performed <<" << std::endl;
std::cerr << "dom(A) : " << domA << std::endl;
std::cerr << "dom(B) : " << domB << std::endl;
// std::cerr << "angle(A) : " << angle(A) << std::endl;
// std::cerr << "angle(B) : " << angle(B) << std::endl;
#endif
if (precision < MAX_PRECISION)
precision = MAX_PRECISION;
std::vector<Point> pA = A;
std::vector<Point> pB = B;
std::vector<Point>* C1 = &pA;
std::vector<Point>* C2 = &pB;
Interval dompA = domA;
Interval dompB = domB;
Interval* dom1 = &dompA;
Interval* dom2 = &dompB;
OptInterval dom;
size_t iter = 0;
while (++iter < 100
&& (dompA.extent() >= precision || dompB.extent() >= precision))
{
#if VERBOSE
std::cerr << "iter: " << iter << std::endl;
#endif
dom = clip<collinear_normal_tag>(*C1, *C2, precision);
if (dom.isEmpty()) {
#if VERBOSE
std::cerr << "dom: empty" << std::endl;
#endif
return;
}
#if VERBOSE
std::cerr << "dom : " << dom << std::endl;
#endif
assert(dom->min() <= dom->max());
map_to(*dom2, *dom);
// it's better to stop before losing computational precision
if (iter > 1 && (dom2->extent() <= MAX_PRECISION))
{
#if VERBOSE
std::cerr << "beyond max precision limit" << std::endl;
#endif
break;
}
portion(*C2, *dom);
if (iter > 1 && is_constant(*C2, precision))
{
#if VERBOSE
std::cerr << "new curve portion pC1 is constant" << std::endl;
#endif
break;
}
// if we have clipped less than 20% than we need to subdive the curve
// with the largest domain into two sub-curves
if ( dom->extent() > MIN_CLIPPED_SIZE_THRESHOLD)
{
#if VERBOSE
std::cerr << "clipped less than 20% : " << dom->extent() << std::endl;
std::cerr << "angle(pA) : " << angle(pA) << std::endl;
std::cerr << "angle(pB) : " << angle(pB) << std::endl;
#endif
std::vector<Point> pC1, pC2;
Interval dompC1, dompC2;
if (dompA.extent() > dompB.extent())
{
if ((dompA.extent() / 2) < MAX_PRECISION)
{
break;
}
pC1 = pC2 = pA;
portion(pC1, H1_INTERVAL);
if (false && is_constant(pC1, precision))
{
#if VERBOSE
std::cerr << "new curve portion pC1 is constant" << std::endl;
#endif
break;
}
portion(pC2, H2_INTERVAL);
if (is_constant(pC2, precision))
{
#if VERBOSE
std::cerr << "new curve portion pC2 is constant" << std::endl;
#endif
break;
}
dompC1 = dompC2 = dompA;
map_to(dompC1, H1_INTERVAL);
map_to(dompC2, H2_INTERVAL);
iterate<collinear_normal_tag>(domsA, domsB, pC1, pB,
dompC1, dompB, precision);
iterate<collinear_normal_tag>(domsA, domsB, pC2, pB,
dompC2, dompB, precision);
}
else
{
if ((dompB.extent() / 2) < MAX_PRECISION)
{
break;
}
pC1 = pC2 = pB;
portion(pC1, H1_INTERVAL);
if (is_constant(pC1, precision))
{
#if VERBOSE
std::cerr << "new curve portion pC1 is constant" << std::endl;
#endif
break;
}
portion(pC2, H2_INTERVAL);
if (is_constant(pC2, precision))
{
#if VERBOSE
std::cerr << "new curve portion pC2 is constant" << std::endl;
#endif
break;
}
dompC1 = dompC2 = dompB;
map_to(dompC1, H1_INTERVAL);
map_to(dompC2, H2_INTERVAL);
iterate<collinear_normal_tag>(domsB, domsA, pC1, pA,
dompC1, dompA, precision);
iterate<collinear_normal_tag>(domsB, domsA, pC2, pA,
dompC2, dompA, precision);
}
return;
}
swap(C1, C2);
swap(dom1, dom2);
#if VERBOSE
std::cerr << "dom(pA) : " << dompA << std::endl;
std::cerr << "dom(pB) : " << dompB << std::endl;
#endif
}
domsA.push_back(dompA);
domsB.push_back(dompB);
}
/*
* get_solutions
*
* input: A, B - set of control points of two Bezier curve
* input: precision - required precision of computation
* input: clip - the routine used for clipping
* output: xs - set of pairs of parameter values
* at which the clipping algorithm converges
*
* This routine is based on the Bezier Clipping Algorithm,
* see: Sederberg - Computer Aided Geometric Design
*/
template <typename Tag>
void get_solutions (std::vector< std::pair<double, double> >& xs,
std::vector<Point> const& A,
std::vector<Point> const& B,
double precision)
{
std::pair<double, double> ci;
std::vector<Interval> domsA, domsB;
iterate<Tag> (domsA, domsB, A, B, UNIT_INTERVAL, UNIT_INTERVAL, precision);
if (domsA.size() != domsB.size())
{
assert (domsA.size() == domsB.size());
}
xs.clear();
xs.reserve(domsA.size());
for (size_t i = 0; i < domsA.size(); ++i)
{
#if VERBOSE
std::cerr << i << " : domA : " << domsA[i] << std::endl;
std::cerr << "extent A: " << domsA[i].extent() << " ";
std::cerr << "precision A: " << get_precision(domsA[i]) << std::endl;
std::cerr << i << " : domB : " << domsB[i] << std::endl;
std::cerr << "extent B: " << domsB[i].extent() << " ";
std::cerr << "precision B: " << get_precision(domsB[i]) << std::endl;
#endif
ci.first = domsA[i].middle();
ci.second = domsB[i].middle();
xs.push_back(ci);
}
}
} /* end namespace bezier_clipping */ } /* end namespace detail */
/*
* find_collinear_normal
*
* input: A, B - set of control points of two Bezier curve
* input: precision - required precision of computation
* output: xs - set of pairs of parameter values
* at which there are collinear normals
*
* This routine is based on the Bezier Clipping Algorithm,
* see: Sederberg, Nishita, 1990 - Curve intersection using Bezier clipping
*/
void find_collinear_normal (std::vector< std::pair<double, double> >& xs,
std::vector<Point> const& A,
std::vector<Point> const& B,
double precision)
{
using detail::bezier_clipping::get_solutions;
using detail::bezier_clipping::collinear_normal_tag;
get_solutions<collinear_normal_tag>(xs, A, B, precision);
}
/*
* find_intersections_bezier_clipping
*
* input: A, B - set of control points of two Bezier curve
* input: precision - required precision of computation
* output: xs - set of pairs of parameter values
* at which crossing happens
*
* This routine is based on the Bezier Clipping Algorithm,
* see: Sederberg, Nishita, 1990 - Curve intersection using Bezier clipping
*/
void find_intersections_bezier_clipping (std::vector< std::pair<double, double> >& xs,
std::vector<Point> const& A,
std::vector<Point> const& B,
double precision)
{
using detail::bezier_clipping::get_solutions;
using detail::bezier_clipping::intersection_point_tag;
get_solutions<intersection_point_tag>(xs, A, B, precision);
}
} // end namespace Geom
/*
Local Variables:
mode:c++
c-file-style:"stroustrup"
c-file-offsets:((innamespace . 0)(inline-open . 0)(case-label . +))
indent-tabs-mode:nil
fill-column:99
End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4:fileencoding=utf-8:textwidth=99 :