我尝试使用CGAL中的Arrangement，但由于不清楚原因，程序在CGAL 4.4中的某些曲线崩溃（在以前的版本4.3中没有这样的问题）。看一下问题的简单概述，曲线是字母D的轮廓，转换成线段：
dDouble dpts { 16.261, 95.267, ... 95.267, 16.261, 95.267};
dPoint pts = ... // converting to exact points with 3 decimal places
Curve_2 cu = Curve_2(pts.begin(), pts.end());
insert(arr, cu); // <---- here crash, supposed bug in CGAL 4.4 ------
此外，insert（）还将空行输出到stdout。我提供了cmake的完整示例 配置文件和程序输出。系统正在运行Linux Mint Petra。
完整计划：
的main.cpp
#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Cartesian.h>
#include <CGAL/Arr_segment_traits_2.h>
#include <CGAL/Arr_polyline_traits_2.h>
#include <CGAL/Arr_curve_data_traits_2.h>
#include <CGAL/Arrangement_with_history_2.h>
#include <CGAL/Arr_extended_dcel.h>
#include <CGAL/intersections.h>
#include <CGAL/Gmpq.h>
typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
typedef typename Kernel::FT Nt;
//***************************************************************
typedef CGAL::Aff_transformation_2<Kernel> Aff_Transformation_2;
typedef CGAL::Point_2<Kernel> Point_2;
//***************************************************************
typedef CGAL::Arr_segment_traits_2<Kernel> Segment_traits_2;
typedef CGAL::Arr_polyline_traits_2<Segment_traits_2> Polyline_traits_2;
typedef Polyline_traits_2::Curve_2 Curve_2;
typedef Polyline_traits_2 Traits_2; // renaming
typedef CGAL::Arr_extended_dcel<Traits_2, int, int, int> Dcel;
typedef CGAL::Arrangement_with_history_2<Traits_2, Dcel> Arrangement_2;
//***************************************************************
typedef CGAL::Gmpq Gmpq;
typedef std::deque<Point_2> dPoint_2;
typedef std::deque<double> dDouble;
#define MULVAL 1000
inline int toInt(double d, int mul) { return int(d*mul + .5); }
inline Gmpq toGmpq(double d, int mul=MULVAL) { return Gmpq(toInt(d,mul), mul); }
inline Point_2 toPoint_2(double x, double y, int mul=MULVAL) { return Point_2( Nt(toGmpq(x,mul)), Nt(toGmpq(y,mul)) ); }
int main() {
// simple D letter outline
dDouble dpts { 16.261, 95.267, 16.261, 48.027, 153.477, 48.027, 164.912, 49.104, 186.691, 51.458, 201.573, 54.251, 211.367, 56.921,
225.415, 61.957, 238.134, 68.049, 249.204, 74.952, 258.604, 82.468, 266.944, 91.033, 272.727, 98.754, 277.419,107.216, 280.673,116.053,
282.289,124.687, 282.364,132.995, 281.97, 136.238, 279.901,144.167, 276.218,152.181, 270.568,160.737, 262.216,170.448, 257.505,174.921,
248.805,181.405, 237.688,187.749, 221.082,195.281, 218.006,196.525, 204.35, 201.024, 187.094,204.993, 183.018,205.735, 165.239,208.084,
147.989,208.866, 16.261,208.866, 16.261,168.055, 38.329,167.772, 38.153, 95.267, 16.261, 95.267};
dPoint_2 pts;
for(int i=0;i<dpts.size()/2;i++) pts.push_back(toPoint_2(dpts[2*i],dpts[2*i+1])); // converting into exact points
for(auto &p : pts) std::cout << p << " | "; std::cout << "\n"; // control output
Arrangement_2 arr; // empty arrangement
Curve_2 cu = Curve_2(pts.begin(), pts.end());
insert(arr, cu); // bug in CGAL 4.4
std::cout << "Working\n";
return 0;
}
的CMakeLists.txt
cmake_minimum_required(VERSION 2.8)
SET(CMAKE_VERBOSE_MAKEFILE ON)
set(XXX main)
project(XXX)
SET(CMAKE_BUILD_TYPE Debug)
set(CMAKE_CXX_FLAGS "-std=c++0x -frounding-math")
find_package(CGAL QUIET COMPONENTS Core )
include( ${CGAL_USE_FILE} )
add_executable(${XXX} ${XXX}.cpp)
输出：cmake。
-- The C compiler identification is GNU 4.8.1
-- The CXX compiler identification is GNU 4.8.1
...
-- Using /usr/bin/c++ compiler.
-- Requested component: Core
-- Requested component: MPFR
-- Requested component: GMP
..
程序输出
16.261 95.267 | 16.261 48.027 | 153.477 48.027 | 164.912 49.104 | 186.691 51.458 | 201.573 54.251 | 211.367 56.921 | 225.415 61.957 |
238.134 68.049 | 249.204 74.952 | 258.604 82.468 | 266.944 91.033 | 272.727 98.754 | 277.419 107.216 | 280.673 116.053 | 282.289 124.687 |
282.364 132.995 | 281.97 136.238 | 279.901 144.167 | 276.218 152.181 | 270.568 160.737 | 262.216 170.448 | 257.505 174.921 | 248.805 181.405 |
237.688 187.749 | 221.082 195.281 | 218.006 196.525 | 204.35 201.024 | 187.094 204.993 | 183.018 205.735 | 165.239 208.084 | 147.989 208.866 |
16.261 208.866 | 16.261 168.055 | 38.329 167.772 | 38.153 95.267 | 16.261 95.267 |
terminate called after throwing an instance of 'CGAL::Precondition_exception'
what(): CGAL ERROR: precondition violation!
Expr: i != INVALID_INDEX
File: /usr/local/include/CGAL/Arr_polyline_traits_2.h
Line: 619
Aborted
答案 0 :(得分：1)
确实是4.4中的错误。
下面的补丁应该修复它。
将在下一次正式修订中修复。
diff --git a/Arrangement_on_surface_2/include/CGAL/Arr_polyline_traits_2.h b/Arrangement_on_surface_2/include/CGAL/Arr_polyline_traits_2.h
index 1a04d7d..aa48ded 100644
--- a/Arrangement_on_surface_2/include/CGAL/Arr_polyline_traits_2.h
+++ b/Arrangement_on_surface_2/include/CGAL/Arr_polyline_traits_2.h
@@ -2742,8 +2742,7 @@ namespace CGAL {
* If q is not in the x-range of cv, returns INVALID_INDEX.
*/
template <typename Compare>
- std::size_t locate_gen(const X_monotone_curve_2& cv,
- Compare compare) const
+ std::size_t locate_gen(const X_monotone_curve_2& cv, Compare compare) const
{
// The direction of cv. SMALLER means left-to-right and
// otherwise right-to-left
@@ -2766,7 +2765,14 @@ namespace CGAL {
Comparison_result res_to = compare(cv[to], ARR_MAX_END);
if (res_to == EQUAL) return to;
- if (res_to == res_from) return INVALID_INDEX;
+ // Check whether the point is either lexicographically to the left of
+ // the curve or lexicographically to the right of the curve.
+ if (res_to == res_from)
+ // If the x-monotone polyline is vertical, return the index of the
+ // segment that is closest to the point. Otherwise, the point is not
+ // in the x-range of the polyline.
+ return (is_vertical_2_object()(cv)) ?
+ ((res_to == SMALLER) ? from : to) : INVALID_INDEX;
// Perform a binary search to locate the segment that contains q in its
// range: