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Coorection to GetLowerSpan method in nurbs_utilitites #13096

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Feb 6, 2025
Merged

Coorection to GetLowerSpan method in nurbs_utilitites #13096

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30085fc
Coorection to GetLowerSpan method in nurbs_utilitites
andrewgorgi Feb 5, 2025
92481ad
Additional test for getLowerSpan in nurbs_utilitites
andrewgorgi Feb 5, 2025
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21 changes: 14 additions & 7 deletions kratos/geometries/nurbs_shape_function_utilities/nurbs_utilities.h
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Original file line number Diff line number Diff line change
Expand Up @@ -12,8 +12,7 @@
// Ported from the ANurbs library (https://github.com/oberbichler/ANurbs)
//

#if !defined(KRATOS_NURBS_UTILITY_H_INCLUDED )
#define KRATOS_NURBS_UTILITY_H_INCLUDED
#pragma once

// System includes

Expand Down Expand Up @@ -64,10 +63,20 @@ namespace NurbsUtilities
inline IndexType GetLowerSpan(
const SizeType PolynomialDegree,
const Vector& rKnots,
const double ParameterT)
const double ParameterT,
const double tolerance = 1e-12)
{
// Check if the ParameterT (gauss point) is coincident to a knot (laying on an edge of a knot span)
double parameter_t_corrected = ParameterT;
for (unsigned i = PolynomialDegree; i < rKnots.size(); i++) {
if (std::abs(ParameterT-rKnots[i]) < tolerance) {
parameter_t_corrected = rKnots[i];
break;
}
}
const auto span = std::lower_bound(std::begin(rKnots) + PolynomialDegree,
std::end(rKnots) - PolynomialDegree, ParameterT) - std::begin(rKnots) - 1;
std::end(rKnots) - PolynomialDegree, parameter_t_corrected) - std::begin(rKnots) - 1;

return span;
}

Expand Down Expand Up @@ -186,6 +195,4 @@ namespace NurbsUtilities
///@}
}; // class NurbsUtility
///@}
} // namespace Kratos

#endif // KRATOS_NURBS_UTILITY_H_INCLUDED defined
} // namespace Kratos
67 changes: 62 additions & 5 deletions kratos/tests/cpp_tests/geometries/test_nurbs_curve_shape_functions.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@ namespace Testing {
typedef std::size_t IndexType;

/// Factory functions
NurbsCurveShapeFunction GenerateReferenceNurbsCurveShapeFunction()
NurbsCurveShapeFunction GenerateReferenceNurbsCurveShapeFunction(double parameter_t)
{
// Assign the polynomial order of the basis
SizeType polynomial_degree = 4;
Expand Down Expand Up @@ -65,9 +65,6 @@ namespace Testing {
weights[6] = 3.550000000000000;
weights[7] = 1.000000000000000;

// Parameter on the curve where to compute the basis functions and their derivatives
double parameter_t = 6.5;

// Create the shape function container
NurbsCurveShapeFunction shape_functions(polynomial_degree, derivative_order);

Expand All @@ -85,7 +82,9 @@ namespace Testing {
KRATOS_TEST_CASE_IN_SUITE(NurbsBasisFunctions1d, KratosCoreNurbsGeometriesFastSuite) {

// Get reference Nurbs curve shape functions
NurbsCurveShapeFunction shape_functions = GenerateReferenceNurbsCurveShapeFunction();
// Parameter on the curve where to compute the basis functions and their derivatives
double parameter_t = 6.5;
NurbsCurveShapeFunction shape_functions = GenerateReferenceNurbsCurveShapeFunction(parameter_t);

// Check the Nurbs basis functions
KRATOS_EXPECT_NEAR(shape_functions(0, 0), 0.040341356830719, TOLERANCE);
Expand Down Expand Up @@ -137,5 +136,63 @@ namespace Testing {
KRATOS_EXPECT_NEAR(shape_functions(4, 6), 0.227141701884515, TOLERANCE);
}


KRATOS_TEST_CASE_IN_SUITE(NurbsBasisFunctions1dCloseToKnot, KratosCoreNurbsGeometriesFastSuite) {

// Get reference Nurbs curve shape functions
// Parameter on the curve where to compute the basis functions and their derivatives
double parameter_t = 4.5+1e-13;
NurbsCurveShapeFunction shape_functions = GenerateReferenceNurbsCurveShapeFunction(parameter_t);

// Check the Nurbs basis functions
KRATOS_EXPECT_NEAR(shape_functions(0, 0), 2.16992e-56 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(1, 0), -1.16534e-41 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(2, 0), 1.41472e-27 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(3, 0), 0.396722 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(4, 0), 0.603278 , TOLERANCE);

// Check the first derivatives of the Nurbs basis functions
KRATOS_EXPECT_NEAR(shape_functions(0, 1), 8.64817e-43 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(1, 1), -3.48334e-28 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(2, 1), 2.81918e-14 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(3, 1), -0.386802 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(4, 1), 0.386802 , TOLERANCE);

// Check the second derivatives of the Nurbs basis functions
KRATOS_EXPECT_NEAR(shape_functions(0, 2), 2.58504e-29 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(1, 2), -6.9414e-15 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(2, 2), 0.280895 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(3, 2), -0.466791 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(4, 2), 0.185896 , TOLERANCE);

// Check the third derivatives of the Nurbs basis functions
KRATOS_EXPECT_NEAR(shape_functions(0, 3), 5.15132e-16 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(1, 3), -0.0691621 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(2, 3), 0.233871 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(3, 3), -0.229086 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(4, 3), 0.0643776 , TOLERANCE);

// Check the fourth derivatives of the Nurbs basis functions
KRATOS_EXPECT_NEAR(shape_functions(0, 4), 0.00513263 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(1, 4), -0.0264787 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(2, 4), 0.0677313 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(3, 4), -0.0644236 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(4, 4), 0.0180384 , TOLERANCE);

// Check the fifth derivatives of the Nurbs basis functions
KRATOS_EXPECT_NEAR(shape_functions(0, 5), -0.00220974 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(1, 5), -0.00372319 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(2, 5), 0.0219781 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(3, 5), -0.0223559 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(4, 5), 0.00631078 , TOLERANCE);

// Check the sixth derivatives of the Nurbs basis functions
KRATOS_EXPECT_NEAR(shape_functions(0, 6), 0.00282508 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(1, 6), -0.00676125 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(2, 6), 0.0108606 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(3, 6), -0.00958053 , TOLERANCE);
KRATOS_EXPECT_NEAR(shape_functions(4, 6), 0.00265608 , TOLERANCE);
}

} // namespace Testing.
} // namespace Kratos.
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