From fa1f85dfe585f616de379ff25830535f5b268475 Mon Sep 17 00:00:00 2001
From: eap <eap@opencascade.com>
Date: Thu, 29 Dec 2005 15:45:10 +0000
Subject: [PATCH] PAL10872. Fix aspect ratio for quadrangles

---
 src/Controls/SMESH_Controls.cxx | 53 +++++++++++++++++++++++++--------
 1 file changed, 40 insertions(+), 13 deletions(-)

diff --git a/src/Controls/SMESH_Controls.cxx b/src/Controls/SMESH_Controls.cxx
index 0e73c4fc8..1dab406f4 100644
--- a/src/Controls/SMESH_Controls.cxx
+++ b/src/Controls/SMESH_Controls.cxx
@@ -254,38 +254,65 @@ SMDSAbs_ElementType MinimumAngle::GetType() const
 */
 double AspectRatio::GetValue( const TSequenceOfXYZ& P )
 {
+  // According to "Mesh quality control" by Nadir Bouhamau referring to
+  // Pascal Jean Frey and Paul-Louis George. Maillages, applications aux elements finis.
+  // Hermes Science publications, Paris 1999 ISBN 2-7462-0024-4
+  // See PAL10872
+
   int nbNodes = P.size();
 
-  if ( nbNodes != 3 && nbNodes != 4 )
+  if ( nbNodes < 3 )
     return 0;
 
   // Compute lengths of the sides
 
-  double aLen[ nbNodes ];
+  vector< double > aLen (nbNodes);
+
   for ( int i = 0; i < nbNodes - 1; i++ )
     aLen[ i ] = getDistance( P( i + 1 ), P( i + 2 ) );
   aLen[ nbNodes - 1 ] = getDistance( P( 1 ), P( nbNodes ) );
 
   // Compute aspect ratio
 
-  if ( nbNodes == 3 ) 
+  if ( nbNodes == 3 )
   {
+    // Q = alfa * h * p / S, where
+    //
+    // alfa = sqrt( 3 ) / 6
+    // h - length of the longest edge
+    // p - half perimeter
+    // S - triangle surface
+
+    const double alfa = sqrt( 3. ) / 6.;
+    double maxLen = Max( aLen[ 0 ], Max( aLen[ 1 ], aLen[ 2 ] ) );
+    double half_perimeter = ( aLen[0] + aLen[1] + aLen[2] ) / 2.;
     double anArea = getArea( P( 1 ), P( 2 ), P( 3 ) );
     if ( anArea <= Precision::Confusion() )
       return 0.;
-    double aMaxLen = Max( aLen[ 0 ], Max( aLen[ 1 ], aLen[ 2 ] ) );
-    static double aCoef = sqrt( 3. ) / 4;
 
-    return aCoef * aMaxLen * aMaxLen / anArea;
+    return alfa * maxLen * half_perimeter / anArea;
   }
   else
   {
-    double aMinLen = Min( Min( aLen[ 0 ], aLen[ 1 ] ), Min( aLen[ 2 ], aLen[ 3 ] ) );
-    if ( aMinLen <= Precision::Confusion() )
-      return 0.;
-    double aMaxLen = Max( Max( aLen[ 0 ], aLen[ 1 ] ), Max( aLen[ 2 ], aLen[ 3 ] ) );
-    
-    return aMaxLen / aMinLen;
+    // return aspect ratio of the worst triange which can be built
+    // taking three nodes of the quadrangle
+    TSequenceOfXYZ triaPnts(3);
+    // triangle on nodes 1 3 2
+    triaPnts(1) = P(1);
+    triaPnts(2) = P(3);
+    triaPnts(3) = P(2);
+    double ar = GetValue( triaPnts );
+    // triangle on nodes 1 3 4
+    triaPnts(3) = P(4);
+    ar = Max ( ar, GetValue( triaPnts ));
+    // triangle on nodes 1 2 4
+    triaPnts(2) = P(2);
+    ar = Max ( ar, GetValue( triaPnts ));
+    // triangle on nodes 3 2 4
+    triaPnts(1) = P(3);
+    ar = Max ( ar, GetValue( triaPnts ));
+
+    return ar;
   }
 }
 
@@ -1116,7 +1143,7 @@ void MultiConnection2D::GetValues(MValues& theValues){
   SMDS_FaceIteratorPtr anIter = myMesh->facesIterator();
   for(; anIter->more(); ){
     const SMDS_MeshFace* anElem = anIter->next();
-    long anElemId = anElem->GetID();
+    //long anElemId = anElem->GetID();
     SMDS_ElemIteratorPtr aNodesIter = anElem->nodesIterator();
     long aNodeId[3];
 
-- 
2.39.2