From: emv <emv@opencascade.com>
Date: Fri, 22 Jul 2016 08:53:07 +0000 (+0300)
Subject: 0027704: Numeric inaccuracy due to huge extension of the offset faces
X-Git-Tag: V7_1_0_beta~235
X-Git-Url: http://git.dev.opencascade.org/gitweb/?p=occt.git;a=commitdiff_plain;h=66cce03ae5e3f7a73951d8e2dbb15cd77ffb2250

0027704: Numeric inaccuracy due to huge extension of the offset faces

The max extension value of the faces in offset operation has been decreased
to 1.e+7 value to avoid the lack of precision in the calculations.

Update of test cases according to the new behavior
---

diff --git a/src/BRepOffset/BRepOffset_Tool.cxx b/src/BRepOffset/BRepOffset_Tool.cxx
index 638b476ae6..356ae06a02 100644
--- a/src/BRepOffset/BRepOffset_Tool.cxx
+++ b/src/BRepOffset/BRepOffset_Tool.cxx
@@ -3211,7 +3211,16 @@ Standard_Boolean BRepOffset_Tool::EnLargeFace
   Standard_Boolean      isVV1degen = Standard_False, isVV2degen = Standard_False;
   Standard_Real         US1,VS1,US2,VS2;
   Standard_Real         UF1,VF1,UF2,VF2;
-  Standard_Real         infini = 1.e8;
+  // The maximal value to enlarge surfaces is decreased to 1.e+7.
+  // It is justified by the floating point format. As we can have only 15
+  // valuable decimal numbers, then during intersection of surfaces with
+  // bounds of 1.e+8 the possible inaccuracy might appear already in seventh
+  // decimal place which will be more than Precision::Confusion value -
+  // 1.e-7, default tolerance value for the section curves.
+  // By decreasing the max enlarge value to 1.e+7 the inaccuracy will be
+  // shifted to eighth decimal place, i.e. the inaccuracy will be
+  // decreased to values less than 1.e-7.
+  Standard_Real         infini = 1.e7;//1.e8;
   Standard_Boolean      SurfaceChange = Standard_False;
 
   if (S->IsUPeriodic() || S->IsVPeriodic()) {
diff --git a/tests/bugs/modalg_6/bug27704 b/tests/bugs/modalg_6/bug27704
new file mode 100644
index 0000000000..ebcd6564f8
--- /dev/null
+++ b/tests/bugs/modalg_6/bug27704
@@ -0,0 +1,22 @@
+puts "========"
+puts "OCC27704"
+puts "========"
+puts ""
+#################################################
+# Numeric inaccuracy due to huge extension of the offset faces
+#################################################
+
+# Input shell contains two planar faces with linear edges.
+# The result of offset operation is also expected to contain
+# only simple geometries (planes, lines, 2d lines).
+# Due to inaccuracy SameParameter can convert 2d lines
+# into 2d BSpline curves.
+
+restore [locate_data_file bug27704.brep] s
+offsetparameter 1e-7 p i
+offsetload s 1
+offsetperform result
+if {[regexp {BSpline} [dump result]]} {
+  puts "Error: BSpline is created"
+}
+
diff --git a/tests/offset/faces_type_i/C8 b/tests/offset/faces_type_i/C8
index 6a79bca7b3..ed4c24eb51 100644
--- a/tests/offset/faces_type_i/C8
+++ b/tests/offset/faces_type_i/C8
@@ -1,5 +1,4 @@
 puts "TODO OCC25406 ALL: Error : The volume of result shape is"
-puts "TODO OCC25406 Windows: Faulty shapes in variables faulty_1 to"
 puts "TODO OCC25406 Linux: Error: bsection of the result and s is not equal to zero"
 
 ellipse w1 0 0 0 15 10
diff --git a/tests/offset/shape_type_i/A5 b/tests/offset/shape_type_i/A5
index 8787c49370..b7213c3d3d 100644
--- a/tests/offset/shape_type_i/A5
+++ b/tests/offset/shape_type_i/A5
@@ -3,4 +3,4 @@ trotate s 0 0 0 0 0 1 90
 
 OFFSETSHAPE 1 {} $calcul $type
 
-checkprops result -v 3.57243e+022
+checkprops result -v 3.57246e+019
diff --git a/tests/offset/shape_type_i/A9 b/tests/offset/shape_type_i/A9
index 2167666ae4..ea8ccdb126 100644
--- a/tests/offset/shape_type_i/A9
+++ b/tests/offset/shape_type_i/A9
@@ -3,4 +3,4 @@ trotate s 0 0 0 0 0 1 90
 
 OFFSETSHAPE 1 {} $calcul $type
 
-checkprops result -v 2.96865e+016
+checkprops result -v 2.96865e+014
diff --git a/tests/offset/shape_type_i/B4 b/tests/offset/shape_type_i/B4
index 925ea33f85..86be03c086 100644
--- a/tests/offset/shape_type_i/B4
+++ b/tests/offset/shape_type_i/B4
@@ -3,4 +3,4 @@ trotate s 0 0 0 0 0 1 90
 
 OFFSETSHAPE 1 {} $calcul $type
 
-checkprops result -v 1.77778e+16
+checkprops result -v 1.77778e+014
diff --git a/tests/offset/shape_type_i/B6 b/tests/offset/shape_type_i/B6
index 6f4eb763c9..fc6d2731d1 100644
--- a/tests/offset/shape_type_i/B6
+++ b/tests/offset/shape_type_i/B6
@@ -4,5 +4,5 @@ psphere s 15 270
 
 OFFSETSHAPE 1 {} $calcul $type
 
-checkprops result -v 1.77778e+16
+checkprops result -v 1.77778e+014
 
diff --git a/tests/offset/shape_type_i/C8 b/tests/offset/shape_type_i/C8
index 1a95d846ac..b2aad80a3d 100644
--- a/tests/offset/shape_type_i/C8
+++ b/tests/offset/shape_type_i/C8
@@ -1,5 +1,4 @@
 puts "TODO OCC23068 ALL: Error : The volume of result shape is"
-puts "TODO OCC23068 Windows: Faulty shapes in variables faulty_1 to"
 puts "TODO OCC23068 Linux: Error: bsection of the result and s is not equal to zero"
 
 ellipse w1 0 0 0 15 10