From: eap <eap@opencascade.com>
Date: Mon, 12 Dec 2005 11:19:33 +0000 (+0000)
Subject: PAL10872. Fix 2D aspect ratio according to Nardir Bouhamou's specification
X-Git-Tag: T_3_1_0pre~10
X-Git-Url: http://git.salome-platform.org/gitweb/?a=commitdiff_plain;h=8a9307decf3e973c08fdf0247b6e03ecfcc35259;p=modules%2Fsmesh.git

PAL10872. Fix 2D aspect ratio according to Nardir Bouhamou's specification
---

diff --git a/src/Controls/SMESH_Controls.cxx b/src/Controls/SMESH_Controls.cxx
index 3ebd18b90..7e6603b61 100644
--- a/src/Controls/SMESH_Controls.cxx
+++ b/src/Controls/SMESH_Controls.cxx
@@ -282,6 +282,10 @@ 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
+
   int nbNodes = P.size();
 
   if ( nbNodes < 3 )
@@ -289,12 +293,7 @@ double AspectRatio::GetValue( const TSequenceOfXYZ& P )
 
   // Compute lengths of the sides
 
-  //double aLen[ nbNodes ];
-#ifndef WNT
-  double aLen [nbNodes];
-#else
-  double* aLen = (double *)new double[nbNodes];
-#endif
+  vector< double > aLen (nbNodes);
 
   for ( int i = 0; i < nbNodes - 1; i++ )
     aLen[ i ] = getDistance( P( i + 1 ), P( i + 2 ) );
@@ -304,30 +303,43 @@ double AspectRatio::GetValue( const TSequenceOfXYZ& P )
 
   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 = aLen[ 0 ];
-    double aMaxLen = aLen[ 0 ];
-
-    for(int i = 1; i < nbNodes ; i++ ){
-      aMinLen = Min( aMinLen, aLen[ i ] );
-      aMaxLen = Max( aMaxLen, aLen[ i ] );
-    }
-#ifdef WNT
-  delete [] aLen;
-#endif
-    if ( aMinLen <= Precision::Confusion() )
-      return 0.;
-
-    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;
   }
 }
 
@@ -447,7 +459,7 @@ double AspectRatio3D::GetValue( const TSequenceOfXYZ& P )
     double aVolume = getVolume(P);
     //double aVolume = getVolume(aLen);
     double aHeight = getMaxHeight(aLen);
-    static double aCoeff = sqrt(6.0)/36.0;
+    static double aCoeff = sqrt(2.0)/12.0;
     aQuality = aCoeff*aHeight*aSumArea/aVolume;
     break;
   }