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[bos #43494] fixed Arithmetic1D discretization and added new error compensation function

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mbs 2024-11-13 15:50:59 +00:00
parent d67308f4f8
commit 63567f57a1
2 changed files with 116 additions and 11 deletions
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7
doc/gui/input/1d_meshing_hypo.rst
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@ -1,4 +1,5 @@
.. _a1d_meshing_hypo_page:
.. |larr| unicode:: U+02190 .. LEFTWARDS ARROW
*********************
1D Meshing Hypotheses
@ -57,7 +58,7 @@ Adaptive hypothesis
Arithmetic Progression hypothesis
#################################
**Arithmetic Progression** hypothesis allows to split edges into segments with a length that changes in arithmetic progression (Lk = Lk-1 + d) beginning from a given starting length and up to a given end length.
**Arithmetic Progression** hypothesis allows to split edges into segments with a length that changes in arithmetic progression (L\ :sub:`k`\ |larr| L\ :sub:`k-1`\ + d) beginning from a given starting length and up to a given end length.
The splitting direction is defined by the orientation of the underlying geometrical edge. **Reverse Edges** list box allows specifying the edges, for which the splitting should be made in the direction opposite to their orientation. This list box is usable only if a geometry object is selected for meshing. In this case it is possible to select edges to be reversed either directly picking them in the 3D viewer or by selecting the edges or groups of edges in the Object Browser. Use
**Add** button to add the selected edges to the list.
@ -82,7 +83,7 @@ The splitting direction is defined by the orientation of the underlying geometri
Geometric Progression hypothesis
################################
**Geometric Progression** hypothesis allows splitting edges into segments with a length that changes in geometric progression (Lk = Lk-1 * d) starting from a given **Start Length** and with a given **Common Ratio**.
**Geometric Progression** hypothesis allows splitting edges into segments with a length that changes in geometric progression (L\ :sub:`k`\ |larr| L\ :sub:`k-1`\ * d) starting from a given **Start Length** and with a given **Common Ratio**.
The splitting direction is defined by the orientation of the underlying geometrical edge.
**Reverse Edges** list box allows specifying the edges, for which the splitting should be made in the direction opposite to their orientation. This list box is usable only if a geometry object is selected for meshing. In this case it is possible to select edges to be reversed either directly picking them in the 3D viewer or by selecting the edges or groups of edges in the Object Browser. Use **Add** button to add the selected edges to the list.
@ -177,7 +178,7 @@ You can set the type of node distribution for this hypothesis in the **Hypothesi
**Scale Distribution** - length of segments gradually changes depending on the **Scale Factor**, which is a ratio of the first segment length to the last segment length.
Length of segments changes in geometric progression with the common ratio (A) depending on the **Scale Factor** (S) and **Number of Segments** (N) as follows: A = S**(1/(N-1)). For an edge of length L, length of the first segment is L * (1 - A)/(1 - A**N)
Length of segments changes in geometric progression with the common ratio (A) depending on the **Scale Factor** (S) and **Number of Segments** (N) as follows: A = S\ :sup:`(1/(N-1))`\ . For an edge of length L, length of the first segment is L * (1 - A)/(1 - A\ :sup:`N`\ )
.. image:: ../images/a-nbsegments2.png
:align: center

120
src/StdMeshers/StdMeshers_Regular_1D.cxx
View File

@ -492,6 +492,105 @@ static void compensateError(double a1, double an,
}
}
//================================================================================
/*!
* \brief adjust internal node parameters so that the last segment length == an,
* and by distributing the error for the total length of curve segments
* in relation to the target length computed from the current parameters
* \param a1 - the first segment length
* \param an - the last segment length
* \param U1 - the first edge parameter
* \param Un - the last edge parameter
* \param length - the edge length
* \param C3d - the edge curve
* \param theParams - internal node parameters to adjust
*/
//================================================================================
static void distributeError(double a1, double an,
double U1, double Un,
double length,
Adaptor3d_Curve& C3d,
list<double> & theParams)
{
// Compute the error of the total length based in the current curve parameters
double tol = Min( Precision::Confusion(), 0.01 * Min(a1, an) );
double totalLength = 0.0;
double prevParam = U1;
list<double> segLengths;
list<double>::iterator itU = theParams.begin();
for ( ; itU != theParams.end(); ++itU )
{
// Compute the curve length between two adjacent parameters and sum them up
double curLength = GCPnts_AbscissaPoint::Length(C3d, prevParam, *itU, tol);
segLengths.push_back(curLength);
totalLength += curLength;
prevParam = *itU;
}
// Calculate the error between the total length of all segments based on given parameters
// and the target length of the edge itself
double error = totalLength - length;
// Compute the sum of all internal segments (= total computed length minus the length of
// the start and end segments)
double midLength = totalLength - (a1 + an);
// We only need to distribute the error, if the current parametrization is not correct,
// and if there are multiple internal segments
smIdType nPar = theParams.size();
if ( a1 + an <= length && nPar > 1 && fabs(error) > tol )
{
// Update the length of each internal segment (start and end length are given and not changed)
double newTotalLength = 0.0;
double newLength;
double relError = error / midLength;
list<double> newSegLengths;
list<double>::iterator itL = segLengths.begin();
for ( ; itL != segLengths.end(); ++itL )
{
// Do not update, but copy the first and the last segment lengths
newLength = *itL;
if (itL != segLengths.begin() && itL != --segLengths.end())
{
newLength -= newLength * relError;
}
newSegLengths.push_back(newLength);
newTotalLength += newLength;
}
bool reverse = ( U1 > Un );
// Update the parameters of the curve based on the new lengths
double curveLength, tol2, U;
double prevU = U1;
itU = theParams.begin();
itL = newSegLengths.begin();
for ( ; itU != theParams.end(); ++itU, ++itL )
{
curveLength = (reverse ? -(*itL) : *itL);
tol2 = Min( Precision::Confusion(), fabs(curveLength) / 100. );
GCPnts_AbscissaPoint Discret( tol2, C3d, curveLength, prevU );
if ( !Discret.IsDone() )
{
return;
}
U = Discret.Parameter();
double sign = reverse ? -1 : 1;
if ( sign*U1 < sign*U && sign*U < sign*Un )
{
*itU = U;
}
else
{
*itU = (sign*U >= sign*Un ? Un : U1);
break;
}
prevU = U;
}
}
}
//================================================================================
/*!
* \brief Class used to clean mesh on edges when 0D hyp modified.
@ -1042,8 +1141,9 @@ bool StdMeshers_Regular_1D::computeInternalParameters(SMESH_Mesh & theMesh,
return error ( SMESH_Comment("Invalid segment lengths (")<<a1<<" and "<<an<<") "<<
"for an edge of length "<<theLength);
double q = ( an - a1 ) / ( 2 *theLength/( a1 + an ) - 1 );
int n = int(fabs(q) > numeric_limits<double>::min() ? ( 1+( an-a1 )/q ) : ( 1+theLength/a1 ));
// Compute first the number of segments and then the arithmetic increment based on that number
int n = static_cast<int>(2 * theLength / ( a1 + an ) + 0.5);
double q = (n > 1 ? ( an - a1 ) / (n - 1) : 0.0);
double U1 = theReverse ? l : f;
double Un = theReverse ? f : l;
@ -1054,19 +1154,23 @@ bool StdMeshers_Regular_1D::computeInternalParameters(SMESH_Mesh & theMesh,
eltSize = -eltSize;
q = -q;
}
while ( n-- > 0 && eltSize * ( Un - U1 ) > 0 ) {
for (int i=0; i<n; i++) {
// computes a point on a curve <theC3d> at the distance <eltSize>
// from the point of parameter <param>.
GCPnts_AbscissaPoint Discret( tol, theC3d, eltSize, param );
if ( !Discret.IsDone() ) break;
param = Discret.Parameter();
if ( param > f && param < l )
theParams.push_back( param );
else
break;
theParams.push_back( param );
eltSize += q;
}
compensateError( a1, an, U1, Un, theLength, theC3d, theParams );
distributeError( a1, an, U1, Un, theLength, theC3d, theParams );
// Do not include the parameter for the start or end of an edge in the list of parameters
// NOTE: it is required to correctly distribute the error
if (fabs(theParams.front() - U1) < tol) theParams.pop_front();
if (fabs(theParams.back() - Un) < tol) theParams.pop_back();
if ( theReverse ) theParams.reverse(); // NPAL18025
return true;