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Add Tolerance to Floating Point Comparisons in find_intersection() #3497

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Add Tolerance to Floating Point Comparisons in find_intersection() #3497

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0197257
add random shifts to find_intersection()
miaoyinb Jun 21, 2023
57bab4b
New unit test
roystgnr Mar 20, 2023
2566914
Unit tests for "tangent" ray/hole intersection
roystgnr Mar 21, 2023
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5 changes: 4 additions & 1 deletion src/mesh/mesh_triangle_holes.C
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Original file line number Diff line number Diff line change
Expand Up @@ -105,11 +105,14 @@ namespace
//
// If the intersection is a "glancing" one at a corner, return -1.
Real find_intersection(const Point & source,
const Point & ray_target,
const Point & ray_target_0,
const Point & edge_pt0,
const Point & edge_pt1,
const Point & edge_pt2)
{
// Add a random small shift to the source and three points
const Point ray_target = ray_target_0 + Point((Real)(rand() % 5000 + 5000) / 5000.0 * libMesh::TOLERANCE * libMesh::TOLERANCE, (Real)(rand() % 5000 + 5000) / 5000.0 * libMesh::TOLERANCE * libMesh::TOLERANCE, 0.0);

// Quick and more numerically stable check
if (!is_intersection(source, ray_target, edge_pt0, edge_pt1))
return -1;
Expand Down
151 changes: 150 additions & 1 deletion tests/mesh/mesh_triangulation.C
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Original file line number Diff line number Diff line change
Expand Up @@ -54,6 +54,10 @@ public:
// This covers an old poly2tri collinearity-tolerance bug
CPPUNIT_TEST( testPoly2TriHolesExtraRefined );

// These cover more recent tolerance issues when verifying holes
CPPUNIT_TEST( testPoly2TriHolePerturbed );
CPPUNIT_TEST( testPoly2TriHoleTangentPerturbed );

CPPUNIT_TEST( testPoly2TriNonUniformRefined );
CPPUNIT_TEST( testPoly2TriHolesNonUniformRefined );
#endif
Expand All @@ -64,6 +68,8 @@ public:
CPPUNIT_TEST( testTriangleInterp );
CPPUNIT_TEST( testTriangleInterp2 );
CPPUNIT_TEST( testTriangleHoles );
CPPUNIT_TEST( testTriangleHolePerturbed );
CPPUNIT_TEST( testTriangleHoleTangentPerturbed );
CPPUNIT_TEST( testTriangleMeshedHoles );
CPPUNIT_TEST( testTriangleEdges );
CPPUNIT_TEST( testTriangleSegments );
Expand All @@ -84,7 +90,7 @@ public:
triangulator.triangulation_type() = TriangulatorInterface::PSLG;

// Don't try to insert points unless we're requested to later
triangulator.desired_area() = 1000;
triangulator.desired_area() = 1e16;
triangulator.minimum_angle() = 0;
triangulator.smooth_after_generating() = false;
triangulator.set_verify_hole_boundaries(true);
Expand Down Expand Up @@ -469,6 +475,109 @@ public:
}


void testTriangulatorHolePerturbed(MeshBase & mesh,
TriangulatorInterface & triangulator)
{
// Points based on a simplification of a hole verification failure
// case
mesh.add_point(Point(100,0), 0);
mesh.add_point(Point(100,100), 1);
mesh.add_point(Point(0,100), 2);
mesh.add_point(Point(-100,100), 3);
mesh.add_point(Point(-100,0), 4);
mesh.add_point(Point(-100,-100), 5);
mesh.add_point(Point(0,-100), 6);
mesh.add_point(Point(100,-100), 7);

commonSettings(triangulator);

// Add a diamond hole in *almost* the center
TriangulatorInterface::PolygonHole
diamond(Point(0,4.e-16),
std::sqrt(2)/2, 4);
const std::vector<TriangulatorInterface::Hole*> holes { &diamond };
triangulator.attach_hole_list(&holes);

triangulator.triangulate();

CPPUNIT_ASSERT_EQUAL(mesh.n_elem(), dof_id_type(12));

// Center coordinates for all the elements we expect
const Real r2p200o6 = (std::sqrt(Real(2))+200)/6,
r2p400o6 = (std::sqrt(Real(2))+400)/6;

std::vector <Point> expected_centers
{ {r2p400o6,100./3}, {-r2p400o6,100./3},
{r2p400o6,-100./3}, {-r2p400o6,-100./3},
{100./3,r2p400o6}, {-100./3,r2p400o6},
{100./3,-r2p400o6}, {-100./3,-r2p400o6},
{r2p200o6,r2p200o6}, {-r2p200o6,r2p200o6},
{r2p200o6,-r2p200o6}, {-r2p200o6,-r2p200o6},
};

testFoundCenters(mesh, expected_centers);
}


void testTriangulatorHoleTangentPerturbed(MeshBase & mesh,
TriangulatorInterface & triangulator)
{
// Points based on a simplification of a hole verification failure
// case
mesh.add_point(Point(200,0), 0);
mesh.add_point(Point(200,100), 1);
mesh.add_point(Point(100,100), 2);
mesh.add_point(Point(0,100), 3);
mesh.add_point(Point(-100,100), 4);
mesh.add_point(Point(-200,100), 5);
mesh.add_point(Point(-200,0), 6);
mesh.add_point(Point(-200,-100), 7);
mesh.add_point(Point(-100,-100), 8);
mesh.add_point(Point(0,-100), 9);
mesh.add_point(Point(100,-100), 10);
mesh.add_point(Point(200,-100), 11);

commonSettings(triangulator);

// Two diamond holes, in *almost* the center of each half of that
// rectangle
TriangulatorInterface::PolygonHole
left_diamond(Point(-100,4.e-16),
std::sqrt(2)/2, 4),
right_diamond(Point(100,-4.e-16),
std::sqrt(2)/2, 4);
const std::vector<TriangulatorInterface::Hole*> holes
{ &left_diamond, &right_diamond };
triangulator.attach_hole_list(&holes);

triangulator.triangulate();

CPPUNIT_ASSERT_EQUAL(mesh.n_elem(), dof_id_type(22));

// Center coordinates for all the elements we expect
const Real r2p200o6 = (std::sqrt(Real(2))+200)/6,
r2p400o6 = (std::sqrt(Real(2))+400)/6;

std::vector <Point> expected_centers
{ {50+r2p400o6,100./3},
{50+r2p400o6,-100./3},
{50+100./3,r2p400o6}, {50-100./3,r2p400o6},
{50+100./3,-r2p400o6}, {50-100./3,-r2p400o6},
{50+r2p200o6,r2p200o6}, {50-r2p200o6,r2p200o6},
{50+r2p200o6,-r2p200o6}, {50-r2p200o6,-r2p200o6},
{50-r2p400o6,100./3},
{50-r2p400o6,-100./3},
{-50+100./3,r2p400o6}, {50-100./3,r2p400o6},
{-50+100./3,-r2p400o6}, {50-100./3,-r2p400o6},
{-50+r2p200o6,r2p200o6}, {50-r2p200o6,r2p200o6},
{-50+r2p200o6,-r2p200o6}, {50-r2p200o6,-r2p200o6},
{0,100./3}, {0,-100./3}
};

testFoundCenters(mesh, expected_centers);
}


void testTriangulatorMeshedHoles(MeshBase & mesh,
TriangulatorInterface & triangulator)
{
Expand Down Expand Up @@ -652,6 +761,26 @@ public:
}


void testTriangleHolePerturbed()
{
LOG_UNIT_TEST;

Mesh mesh(*TestCommWorld);
TriangleInterface triangle(mesh);
testTriangulatorHolePerturbed(mesh, triangle);
}


void testTriangleHoleTangentPerturbed()
{
LOG_UNIT_TEST;

Mesh mesh(*TestCommWorld);
TriangleInterface triangle(mesh);
testTriangulatorHoleTangentPerturbed(mesh, triangle);
}


void testTriangleMeshedHoles()
{
LOG_UNIT_TEST;
Expand Down Expand Up @@ -736,6 +865,26 @@ public:
}


void testPoly2TriHolePerturbed()
{
LOG_UNIT_TEST;

Mesh mesh(*TestCommWorld);
Poly2TriTriangulator p2t_tri(mesh);
testTriangulatorHolePerturbed(mesh, p2t_tri);
}


void testPoly2TriHoleTangentPerturbed()
{
LOG_UNIT_TEST;

Mesh mesh(*TestCommWorld);
Poly2TriTriangulator p2t_tri(mesh);
testTriangulatorHoleTangentPerturbed(mesh, p2t_tri);
}


void testPoly2TriMeshedHoles()
{
LOG_UNIT_TEST;
Expand Down