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ClipperOffset: fixed bug where rounding wasn't entirely accurate //#724
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@AngusJohnson
AngusJohnson committed Nov 25, 2023
1 parent 9299eb6 commit 906bc1d
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Showing 8 changed files with 292 additions and 104 deletions.
18 changes: 12 additions & 6 deletions CPP/Clipper2Lib/include/clipper2/clipper.core.h
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
/*******************************************************************************
* Author : Angus Johnson *
* Date : 22 November 2023 *
* Date : 24 November 2023 *
* Website : http://www.angusj.com *
* Copyright : Angus Johnson 2010-2023 *
* Purpose : Core Clipper Library structures and functions *
Expand Down Expand Up @@ -729,8 +729,9 @@ namespace Clipper2Lib
}
}

inline Point64 GetClosestPointOnSegment(const Point64& offPt,
const Point64& seg1, const Point64& seg2)
template<typename T>
inline Point<T> GetClosestPointOnSegment(const Point<T>& offPt,
const Point<T>& seg1, const Point<T>& seg2)
{
if (seg1.x == seg2.x && seg1.y == seg2.y) return seg1;
double dx = static_cast<double>(seg2.x - seg1.x);
Expand All @@ -740,9 +741,14 @@ namespace Clipper2Lib
static_cast<double>(offPt.y - seg1.y) * dy) /
(Sqr(dx) + Sqr(dy));
if (q < 0) q = 0; else if (q > 1) q = 1;
return Point64(
seg1.x + static_cast<int64_t>(nearbyint(q * dx)),
seg1.y + static_cast<int64_t>(nearbyint(q * dy)));
if constexpr (std::numeric_limits<T>::is_integer)
return Point<T>(
seg1.x + static_cast<T>(nearbyint(q * dx)),
seg1.y + static_cast<T>(nearbyint(q * dy)));
else
return Point<T>(
seg1.x + static_cast<T>(q * dx),
seg1.y + static_cast<T>(q * dy));
}

enum class PointInPolygonResult { IsOn, IsInside, IsOutside };
Expand Down
8 changes: 4 additions & 4 deletions CPP/Clipper2Lib/include/clipper2/clipper.engine.h
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Original file line number Diff line number Diff line change
Expand Up @@ -282,11 +282,11 @@ namespace Clipper2Lib {
void AddPaths(const Paths64& paths, PathType polytype, bool is_open);
public:
virtual ~ClipperBase();
int ErrorCode() { return error_code_; };
int ErrorCode() const { return error_code_; };
void PreserveCollinear(bool val) { preserve_collinear_ = val; };
bool PreserveCollinear() { return preserve_collinear_;};
bool PreserveCollinear() const { return preserve_collinear_;};
void ReverseSolution(bool val) { reverse_solution_ = val; };
bool ReverseSolution() { return reverse_solution_; };
bool ReverseSolution() const { return reverse_solution_; };
void Clear();
void AddReuseableData(const ReuseableDataContainer64& reuseable_data);
#ifdef USINGZ
Expand Down Expand Up @@ -419,7 +419,7 @@ namespace Clipper2Lib {
PolyPathDList::const_iterator end() const { return childs_.cend(); }

void SetScale(double value) { scale_ = value; }
double Scale() { return scale_; }
double Scale() const { return scale_; }

PolyPathD* AddChild(const Path64& path) override
{
Expand Down
19 changes: 14 additions & 5 deletions CPP/Clipper2Lib/src/clipper.offset.cpp
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Original file line number Diff line number Diff line change
@@ -1,6 +1,6 @@
/*******************************************************************************
* Author : Angus Johnson *
* Date : 22 November 2023 *
* Date : 25 November 2023 *
* Website : http://www.angusj.com *
* Copyright : Angus Johnson 2010-2023 *
* Purpose : Path Offset (Inflate/Shrink) *
Expand Down Expand Up @@ -411,19 +411,28 @@ void ClipperOffset::OffsetPoint(Group& group, const Path64& path, size_t j, size
}
else if (cos_a > 0.999) // almost straight - less than 2.5 degree (#424, #526)
{
DoMiter(path, j, k, cos_a);
// with ::Round, preserving near exact delta is more important than simpler paths
// See also Issues #424, #526 #482
if (join_type_ == JoinType::Round)
{
path_out.push_back(GetPerpendic(path[j], norms[k], group_delta_));
path_out.push_back(GetPerpendic(path[j], norms[j], group_delta_));
}
else
DoMiter(path, j, k, cos_a);
}
else if (join_type_ == JoinType::Miter)
{
// miter unless the angle is so acute the miter would exceeds ML
if (cos_a > temp_lim_ - 1) DoMiter(path, j, k, cos_a);
else DoSquare(path, j, k);
}
else if (cos_a > 0.99 || join_type_ == JoinType::Bevel)
// ie > 2.5 deg (see above) but less than ~8 deg ( acos(0.99) )
DoBevel(path, j, k);
else if (join_type_ == JoinType::Round)
DoRound(path, j, k, std::atan2(sin_a, cos_a));
else if (/*cos_a > 0.99 || */ join_type_ == JoinType::Bevel)
// cos_a > 0.99 here improves performance with extremely minor reduction in accuracy
// acos(0.99) == 8.1 deg. still a small angle but not as small as cos_a > 0.999 (see above)
DoBevel(path, j, k);
else
DoSquare(path, j, k);
}
Expand Down
207 changes: 194 additions & 13 deletions CPP/Tests/TestOffsets.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ TEST(Clipper2Tests, TestOffsets2) { // see #448 & #456
if (d < delta * 2)
{
if (d < min_dist) min_dist = d;
if (d > max_dist) max_dist = d;
if (d> max_dist) max_dist = d;
}
prevPt = pt;
}
Expand Down Expand Up @@ -119,33 +119,29 @@ TEST(Clipper2Tests, TestOffsets4) // see #482
{40000, 0}, {40000, 50000}, {0, 50000}, {0, 0}} };
Paths64 solution = InflatePaths(paths, -5000,
JoinType::Square, EndType::Polygon);
std::cout << solution[0].size() << std::endl;

//std::cout << solution[0].size() << std::endl;
EXPECT_EQ(solution[0].size(), 5);

paths = { { {0, 0}, {20000, 400},
{40000, 0}, {40000, 50000}, {0, 50000}, {0, 0}} };
solution = InflatePaths(paths, -5000,
JoinType::Square, EndType::Polygon);
std::cout << solution[0].size() << std::endl;

//std::cout << solution[0].size() << std::endl;
EXPECT_EQ(solution[0].size(), 5);

paths = { { {0, 0}, {20000, 400},
{40000, 0}, {40000, 50000}, {0, 50000}, {0, 0}} };
solution = InflatePaths(paths, -5000,
JoinType::Round, EndType::Polygon);
std::cout << solution[0].size() << std::endl;

EXPECT_EQ(solution[0].size(), 5);
JoinType::Round, EndType::Polygon, 2, 100);
//std::cout << solution[0].size() << std::endl;
EXPECT_GT(solution[0].size(), 5);

paths = { { {0, 0}, {20000, 1500},
{40000, 0}, {40000, 50000}, {0, 50000}, {0, 0}} };
solution = InflatePaths(paths, -5000,
JoinType::Round, EndType::Polygon);
std::cout << solution[0].size() << std::endl;

EXPECT_GT(solution[0].size(), 6);
JoinType::Round, EndType::Polygon, 2, 100);
//std::cout << solution[0].size() << std::endl;
EXPECT_GT(solution[0].size(), 5);
}

TEST(Clipper2Tests, TestOffsets5) // modified from #593 (tests offset clean up)
Expand Down Expand Up @@ -427,3 +423,188 @@ TEST(Clipper2Tests, TestOffsets7) // (#593 & #715)
solution = InflatePaths(subject, -50, JoinType::Miter, EndType::Polygon);
EXPECT_EQ(solution.size(), 0);
}

struct OffsetQual
{
double smallestDist;
double largestDist;
size_t idxSmallestIn; //index to first segment pt
size_t idxSmallestOut;
size_t idxLargestIn; //index to first segment pt
size_t idxLargestOut;
double standardDev;
};

template<typename T>
static OffsetQual GetOffsetQuality(const Path<T>& input, const Path<T>& output, const double desiredDist)
{
if (!input.size() || !output.size()) return OffsetQual();

double desiredDistSqr = desiredDist * desiredDist;
double smallestSqr = desiredDistSqr, largestSqr = desiredDistSqr;
double deviationsSqr = 0;
size_t smallestInIdx = 0, largestInIdx = 0, smallestOutIdx = 0, largestOutIdx = 0;
size_t outIdx = 0;
for (const Point<T>& outPt : output)
{
double closestDistSqr = std::numeric_limits<double>::infinity();

size_t cpi = 0; //closest point index
Point<T> in_prev = input[input.size() - 1];
for (size_t i = 0; i < input.size(); ++i)
{
Point<T> cp = Clipper2Lib::GetClosestPointOnSegment(outPt, input[i], in_prev);
in_prev = input[i];
const double sqrDist = Clipper2Lib::DistanceSqr(cp, outPt);
if (sqrDist < closestDistSqr) { closestDistSqr = sqrDist; cpi = i; };
}

if (closestDistSqr < smallestSqr)
{
smallestSqr = closestDistSqr;
smallestInIdx = cpi;
smallestOutIdx = outIdx;
}
if (closestDistSqr > largestSqr)
{
largestSqr = closestDistSqr;
largestInIdx = cpi;
largestOutIdx = outIdx;
}
// we now have smallestDistSqr between outPt and the input path
double offset_qual = std::sqrt(closestDistSqr) - desiredDist;
deviationsSqr += offset_qual * offset_qual;
++outIdx;
}
OffsetQual oq{};
oq.smallestDist = std::sqrt(smallestSqr);
oq.largestDist = std::sqrt(largestSqr);
oq.idxSmallestIn = smallestInIdx == 0 ? input.size() - 1 : smallestInIdx - 1;
oq.idxLargestIn = largestInIdx == 0 ? input.size() - 1 : largestInIdx - 1;
oq.idxSmallestOut = smallestOutIdx;
oq.idxLargestOut = largestOutIdx;
oq.standardDev = std::sqrt(deviationsSqr / input.size());
return oq;
}

TEST(Clipper2Tests, TestOffsets8) // (#724)
{
Paths64 subject = { MakePath({
91759700, -49711991, 83886095, -50331657,
-872415388, -50331657, -880288993, -49711991, -887968725, -47868251,
-895265482, -44845834, -901999593, -40719165, -908005244, -35589856,
-913134553, -29584205, -917261224, -22850094, -920283639, -15553337,
-922127379, -7873605, -922747045, 0, -922747045, 1434498600,
-922160557, 1442159790, -920414763, 1449642437, -917550346, 1456772156,
-913634061, 1463382794, -908757180, 1469320287, -903033355, 1474446264,
-896595982, 1478641262, -889595081, 1481807519, -882193810, 1483871245,
-876133965, 1484596521, -876145751, 1484713389, -875781839, 1485061090,
-874690056, 1485191762, -874447580, 1485237014, -874341490, 1485264094,
-874171960, 1485309394, -873612294, 1485570372, -873201878, 1485980788,
-872941042, 1486540152, -872893274, 1486720070, -872835064, 1487162210,
-872834788, 1487185500, -872769052, 1487406000, -872297948, 1487583168,
-871995958, 1487180514, -871995958, 1486914040, -871908872, 1486364208,
-871671308, 1485897962, -871301302, 1485527956, -870835066, 1485290396,
-870285226, 1485203310, -868659019, 1485203310, -868548443, 1485188472,
-868239649, 1484791011, -868239527, 1484783879, -838860950, 1484783879,
-830987345, 1484164215, -823307613, 1482320475, -816010856, 1479298059,
-809276745, 1475171390, -803271094, 1470042081, -752939437, 1419710424,
-747810128, 1413704773, -743683459, 1406970662, -740661042, 1399673904,
-738817302, 1391994173, -738197636, 1384120567, -738197636, 1244148246,
-738622462, 1237622613, -739889768, 1231207140, -802710260, 995094494,
-802599822, 995052810, -802411513, 994586048, -802820028, 993050638,
-802879992, 992592029, -802827240, 992175479, -802662144, 991759637,
-802578556, 991608039, -802511951, 991496499, -801973473, 990661435,
-801899365, 990554757, -801842657, 990478841, -801770997, 990326371,
-801946911, 989917545, -801636397, 989501855, -801546099, 989389271,
-800888669, 988625013, -800790843, 988518907, -800082405, 987801675,
-799977513, 987702547, -799221423, 987035738, -799109961, 986944060,
-798309801, 986330832, -798192297, 986247036, -797351857, 985690294,
-797228867, 985614778, -796352124, 985117160, -796224232, 985050280,
-795315342, 984614140, -795183152, 984556216, -794246418, 984183618,
-794110558, 984134924, -793150414, 983827634, -793011528, 983788398,
-792032522, 983547874, -791891266, 983518284, -790898035, 983345662,
-790755079, 983325856, -789752329, 983221956, -789608349, 983212030,
-787698545, 983146276, -787626385, 983145034, -536871008, 983145034,
-528997403, 982525368, -521317671, 980681627, -514020914, 977659211,
-507286803, 973532542, -501281152, 968403233, -496151843, 962397582,
-492025174, 955663471, -489002757, 948366714, -487159017, 940686982,
-486539351, 932813377, -486539351, 667455555, -486537885, 667377141,
-486460249, 665302309, -486448529, 665145917, -486325921, 664057737,
-486302547, 663902657, -486098961, 662826683, -486064063, 662673784,
-485780639, 661616030, -485734413, 661466168, -485372735, 660432552,
-485315439, 660286564, -484877531, 659282866, -484809485, 659141568,
-484297795, 658173402, -484219379, 658037584, -483636768, 657110363,
-483548422, 656980785, -482898150, 656099697, -482800368, 655977081,
-482086070, 655147053, -481979398, 655032087, -481205068, 654257759,
-481090104, 654151087, -480260074, 653436789, -480137460, 653339007,
-479256372, 652688735, -479126794, 652600389, -478199574, 652017779,
-478063753, 651939363, -477095589, 651427672, -476954289, 651359626,
-475950593, 650921718, -475804605, 650864422, -474770989, 650502744,
-474621127, 650456518, -473563373, 650173094, -473410475, 650138196,
-472334498, 649934610, -472179420, 649911236, -471091240, 649788626,
-470934848, 649776906, -468860016, 649699272, -468781602, 649697806,
-385876037, 649697806, -378002432, 649078140, -370322700, 647234400,
-363025943, 644211983, -356291832, 640085314, -350286181, 634956006,
-345156872, 628950354, -341030203, 622216243, -338007786, 614919486,
-336164046, 607239755, -335544380, 599366149, -335544380, 571247184,
-335426942, 571236100, -335124952, 570833446, -335124952, 569200164,
-335037864, 568650330, -334800300, 568184084, -334430294, 567814078,
-333964058, 567576517, -333414218, 567489431, -331787995, 567489431,
-331677419, 567474593, -331368625, 567077133, -331368503, 567070001,
-142068459, 567070001, -136247086, 566711605, -136220070, 566848475,
-135783414, 567098791, -135024220, 567004957, -134451560, 566929159,
-134217752, 566913755, -133983942, 566929159, -133411282, 567004957,
-132665482, 567097135, -132530294, 567091859, -132196038, 566715561,
-132195672, 566711157, -126367045, 567070001, -33554438, 567070001,
-27048611, 566647761, -20651940, 565388127, -14471751, 563312231,
-8611738, 560454902, 36793963, 534548454, 43059832, 530319881,
48621743, 525200596, 53354240, 519306071, 57150572, 512769270,
59925109, 505737634, 61615265, 498369779, 62182919, 490831896,
62182919, 474237629, 62300359, 474226543, 62602349, 473823889,
62602349, 472190590, 62689435, 471640752, 62926995, 471174516,
63297005, 470804506, 63763241, 470566946, 64313081, 470479860,
65939308, 470479860, 66049884, 470465022, 66358678, 470067562,
66358800, 470060430, 134217752, 470060430, 134217752, 0,
133598086, -7873605, 131754346, -15553337, 128731929, -22850094,
124605260, -29584205, 119475951, -35589856, 113470300, -40719165,
106736189, -44845834, 99439432, -47868251, 91759700, -49711991
}) };

Paths64 solution;
ClipperOffset c;
double offset = -50329979.0, arc_tol = 2500.0;

c.AddPaths(subject, JoinType::Round, EndType::Polygon);
c.ArcTolerance(arc_tol);
c.MiterLimit(2.0);
c.Execute(offset, solution);

offset = std::abs(offset);
OffsetQual offset_qual = GetOffsetQuality(subject[0], solution[0], std::abs(offset));
/*
std::cout.imbue(std::locale(""));
std::cout << std::setprecision(2) << std::fixed << std::setfill(' ');
std::cout << "Max dist. short of specified offset : "
<< std::setw(12) << (offset - offset_qual.smallestDist) << std::endl;
std::cout << "Max dist. beyond specified offset : "
<< std::setw(12) << (offset_qual.largestDist - offset) << std::endl;
std::cout.imbue(std::locale("C")); //remove thousands separator
Point64 inPt = subject[0][offset_qual.idxSmallestIn];
Point64 outPt = solution[0][offset_qual.idxSmallestOut];
std::cout << "Distance less than delta" << std::endl;
std::cout << "Point in subject : " << inPt << std::endl;
std::cout << "Point in result : " << outPt << std::endl;
inPt = subject[0][offset_qual.idxLargestIn];
outPt = solution[0][offset_qual.idxLargestOut];
std::cout << "Distance greater than delta" << std::endl;
std::cout << "Point in subject : " << inPt << std::endl;
std::cout << "Point in result : " << outPt << std::endl;
std::cout << "StdDev of dist from specified offset : "
<< std::setw(12) << offset_qual.standardDev << std::endl << std::endl;
*/
EXPECT_LE(std::abs(offset) - offset_qual.smallestDist , arc_tol);
}
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