0027720: HLRBrep_Algo BSpline missing edges

The algorithm that builds outlines ("silhouettes") makes an outline in 2d parametric space of the surface starting from some previously detected point where normal is orthogonal to direction of view. So, the surface is previously discretized into (m*n) sample points and some of them become starting points for future outlines.

    If the surface has non-uniform parametrization and/or some local extremums of curvature, the outlines can not be built without breaks, so there are several groups of consequent outlines in this case. Unfortunately, it leads to the situation when current number of sample points becomes insufficient to build all the parts of outlines.

    The idea is to detect the "holes" between already constructed parts of outlines and then complete the construction.

New auxiliary draw command for testing of HLR.

Correction according to the remarks.

Update of test case according to the developer's directive

tests/bugs/modalg_6/bug27341_303

@@ -23,6 +23,6 @@ build3d result
 fit
 
 checkprops result -l 3249.9
-checknbshapes result -vertex 634 -edge 317
+checknbshapes result -vertex 636 -edge 318
 
 checkview -screenshot -2d -path ${imagedir}/${test_image}.png

tests/bugs/modalg_6/bug27720_1

@@ -0,0 +1,26 @@
+puts "============"
+puts "OCC27720"
+puts "============"
+puts ""
+######################################################
+# HLRBrep_Algo BSpline missing edges
+######################################################
+
+pload QAcommands
+
+restore [locate_data_file bug27720_BSpline.brep] a
+
+set viewname "axo"
+
+top
+clear
+
+OCC27341 result a ${viewname}
+build3d result
+
+fit
+
+checkprops result -l 0.883462
+checknbshapes result -vertex 86 -edge 43
+
+checkview -screenshot -2d -path ${imagedir}/${test_image}.png

tests/bugs/modalg_6/bug27720_2

@@ -20,7 +20,7 @@ build3d result
 
 fit
 
-checkprops result -l 0.980942
-checknbshapes result -vertex 54 -edge 27
+checkprops result -l 0.980943
+checknbshapes result -vertex 58 -edge 29
 
 checkview -screenshot -2d -path ${imagedir}/${test_image}.png

tests/bugs/modalg_6/bug27720_4

@@ -0,0 +1,26 @@
+puts "============"
+puts "OCC27720"
+puts "============"
+puts ""
+######################################################
+# HLRBrep_Algo BSpline missing edges
+######################################################
+
+pload QAcommands
+
+restore [locate_data_file bug27720_BSpline.brep] a
+
+set viewname "left"
+
+top
+clear
+
+OCC27341 result a ${viewname}
+build3d result
+
+fit
+
+checkprops result -l 0.820309
+checknbshapes result -vertex 74 -edge 37
+
+checkview -screenshot -2d -path ${imagedir}/${test_image}.png

tests/bugs/modalg_6/bug27720_5

@@ -0,0 +1,26 @@
+puts "============"
+puts "OCC27720"
+puts "============"
+puts ""
+######################################################
+# HLRBrep_Algo BSpline missing edges
+######################################################
+
+pload QAcommands
+
+restore [locate_data_file bug27720_BSpline.brep] a
+
+set viewname "right"
+
+top
+clear
+
+OCC27341 result a ${viewname}
+build3d result
+
+fit
+
+checkprops result -l 0.841499
+checknbshapes result -vertex 92 -edge 46
+
+checkview -screenshot -2d -path ${imagedir}/${test_image}.png