0028493: [Regression vs 7.0.0] Intersection algorithm produces curve with loop

1. New testgrid "lowalgos/intss" has been created. It will contain all test cases on geometrical intersection of two surfaces ("intersect" DRAW-command) and two faces ("bopcurves" DRAW-command).

2. New test case for the issue #28493 has been created because the problem is not reproduced on MASTER.

3. Test case (lowalgos/intss/bug24472) for the issue #29501 has been modified in order to check loops of the resulting intersection curves.

tests/lowalgos/grids.list

@@ -2,4 +2,5 @@
 002 bnd
 003 extcs
 004 extcc
-005 2dgcc
+005 2dgcc
+006 intss

tests/lowalgos/intss/begin

@@ -0,0 +1,30 @@
+# Checks whether theCurve has a loop/bend
+# Use: CheckLoops curve CosMaxAngle [theNbPoints]}
+# theNbPoints sets the interval of discretization;
+# theCosMaxAngle sets the maximal rotation angle between two adjacent segments. This value must be equal to the cosine of this angle.
+
+help CheckLoops {curve CosMaxAngle theNbPoints }
+proc CheckLoops {theCurve theCosMaxAngle {theNbPoints 1000.0}} {
+  upvar #0 $theCurve aCurve
+  bounds aCurve U1 U2
+    
+  set delta [dval (U2-U1)/$theNbPoints]
+  cvalue aCurve [dval U1] xp yp zp dx1 dy1 dz1
+  
+  for {set p [dval U1]} {$p <= [dval U2]} {set p [expr $p + $delta]} {
+    cvalue aCurve $p xp yp zp dx2 dy2 dz2
+    
+    #Check if the angle between the vectors {dx1 dy1 dz1} and {dx2 dy2 dz2} is less than 30deg.
+    set nv1 [ dval dx1*dx1+dy1*dy1+dz1*dz1 ] 
+    set nv2 [ dval dx2*dx2+dy2*dy2+dz2*dz2 ] 
+    set dp [ dval dx1*dx2+dy2*dy2+dz1*dz2 ] 
+    
+    if {$dp < [ expr $theCosMaxAngle * sqrt($nv1 * $nv2) ] } {
+      puts "Error: The curve aCurve is possible to have a bend at parameter $p. Please check carefully"
+    }      
+    
+    dset dx1 dx2
+    dset dy1 dy2
+    dset dz1 dz2
+  }
+}

tests/lowalgos/intss/bug24472

@@ -32,6 +32,9 @@ foreach c [directory ii12*] {
     puts "Error: Wrong curve's range!"
   }
   
+  # cos(~75.5deg)
+  CheckLoops $c 0.25
+  
   xdistcs $c s1 U1 U2 10 $MaxToler
   xdistcs $c s2 U1 U2 10 $MaxToler
 }
@@ -58,6 +61,9 @@ foreach c [directory ii13*] {
     puts "Error: Wrong curve's range!"
   }
   
+  # cos(~75.5deg)
+  CheckLoops $c 0.25
+
   xdistcs $c s1 U1 U2 10 $MaxToler
   xdistcs $c s2 U1 U2 10 $MaxToler
 }