Merge pull request #43 from AndriyAndreyev/stability_fixes

Stability fixes
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Jan Niklas Hasse 2022-05-20 15:46:44 +02:00 committed by GitHub
commit 81612cb108
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4 changed files with 87 additions and 0 deletions

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@ -262,6 +262,35 @@ void Sweep::FillAdvancingFront(SweepContext& tcx, Node& n)
} }
// True if HoleAngle exceeds 90 degrees. // True if HoleAngle exceeds 90 degrees.
// LargeHole_DontFill checks if the advancing front has a large hole.
// A "Large hole" is a triangle formed by a sequence of points in the advancing
// front where three neighbor points form a triangle.
// And angle between left-top, bottom, and right-top points is more than 90 degrees.
// The first part of the algorithm reviews only three neighbor points, e.g. named A, B, C.
// Additional part of this logic reviews a sequence of 5 points -
// additionally reviews one point before and one after the sequence of three (A, B, C),
// e.g. named X and Y.
// In this case, angles are XBC and ABY and this if angles are negative or more
// than 90 degrees LargeHole_DontFill returns true.
// But there is a configuration when ABC has a negative angle but XBC or ABY is less
// than 90 degrees and positive.
// Then function LargeHole_DontFill return false and initiates filling.
// This filling creates a triangle ABC and adds it to the advancing front.
// But in the case when angle ABC is negative this triangle goes inside the advancing front
// and can intersect previously created triangles.
// This triangle leads to making wrong advancing front and problems in triangulation in the future.
// Looks like such a triangle should not be created.
// The simplest way to check and fix it is to check an angle ABC.
// If it is negative LargeHole_DontFill should return true and
// not initiate creating the ABC triangle in the advancing front.
// X______A Y
// \ /
// \ /
// \ B /
// | /
// | /
// |/
// C
bool Sweep::LargeHole_DontFill(const Node* node) const { bool Sweep::LargeHole_DontFill(const Node* node) const {
const Node* nextNode = node->next; const Node* nextNode = node->next;
@ -269,6 +298,9 @@ bool Sweep::LargeHole_DontFill(const Node* node) const {
if (!AngleExceeds90Degrees(node->point, nextNode->point, prevNode->point)) if (!AngleExceeds90Degrees(node->point, nextNode->point, prevNode->point))
return false; return false;
if (AngleIsNegative(node->point, nextNode->point, prevNode->point))
return true;
// Check additional points on front. // Check additional points on front.
const Node* next2Node = nextNode->next; const Node* next2Node = nextNode->next;
// "..Plus.." because only want angles on same side as point being added. // "..Plus.." because only want angles on same side as point being added.
@ -283,6 +315,11 @@ bool Sweep::LargeHole_DontFill(const Node* node) const {
return true; return true;
} }
bool Sweep::AngleIsNegative(const Point* origin, const Point* pa, const Point* pb) const {
const double angle = Angle(origin, pa, pb);
return angle < 0;
}
bool Sweep::AngleExceeds90Degrees(const Point* origin, const Point* pa, const Point* pb) const { bool Sweep::AngleExceeds90Degrees(const Point* origin, const Point* pa, const Point* pb) const {
const double angle = Angle(origin, pa, pb); const double angle = Angle(origin, pa, pb);
return ((angle > PI_div2) || (angle < -PI_div2)); return ((angle > PI_div2) || (angle < -PI_div2));

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@ -171,6 +171,7 @@ private:
// Decision-making about when to Fill hole. // Decision-making about when to Fill hole.
// Contributed by ToolmakerSteve2 // Contributed by ToolmakerSteve2
bool LargeHole_DontFill(const Node* node) const; bool LargeHole_DontFill(const Node* node) const;
bool AngleIsNegative(const Point* origin, const Point* pa, const Point* pb) const;
bool AngleExceeds90Degrees(const Point* origin, const Point* pa, const Point* pb) const; bool AngleExceeds90Degrees(const Point* origin, const Point* pa, const Point* pb) const;
bool AngleExceedsPlus90DegreesOrIsNegative(const Point* origin, const Point* pa, const Point* pb) const; bool AngleExceedsPlus90DegreesOrIsNegative(const Point* origin, const Point* pa, const Point* pb) const;
double Angle(const Point* origin, const Point* pa, const Point* pb) const; double Angle(const Point* origin, const Point* pa, const Point* pb) const;

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@ -0,0 +1,14 @@
450 2250
450 1750
400 1700
350 1650
350 500
1050 1700
HOLE
980 1636
950 1600
650 1230
625 1247
600 1250
591 1350
550 2050

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@ -188,6 +188,41 @@ BOOST_AUTO_TEST_CASE(PolygonTest03)
} }
} }
BOOST_AUTO_TEST_CASE(PolygonTest04)
{
std::vector<p2t::Point*> polyline {
new p2t::Point(450, 2250),
new p2t::Point(450, 1750),
new p2t::Point(400, 1700),
new p2t::Point(350, 1650),
new p2t::Point(350, 500),
new p2t::Point(1050, 1700)
};
std::vector<p2t::Point*> hole {
new p2t::Point(980, 1636),
new p2t::Point(950, 1600),
new p2t::Point(650, 1230),
new p2t::Point(625, 1247),
new p2t::Point(600, 1250),
new p2t::Point(591, 1350),
new p2t::Point(550, 2050)
};
p2t::CDT cdt{ polyline };
cdt.AddHole(hole);
BOOST_CHECK_NO_THROW(cdt.Triangulate());
const auto result = cdt.GetTriangles();
BOOST_REQUIRE_EQUAL(result.size(), 13);
for (const auto p : polyline) {
delete p;
}
for (const auto p : hole) {
delete p;
}
}
BOOST_AUTO_TEST_CASE(TestbedFilesTest) BOOST_AUTO_TEST_CASE(TestbedFilesTest)
{ {
for (const auto& filename : { "custom.dat", "diamond.dat", "star.dat", "test.dat" }) { for (const auto& filename : { "custom.dat", "diamond.dat", "star.dat", "test.dat" }) {