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IDProjectCategoryView StatusDate SubmittedLast Update
0026495Open CASCADE[OCCT] OCCT:Shape Healingpublic2015-07-29 10:392015-07-29 10:53
Reportermsv
Assigned Togka
PrioritynormalSeverityminor
StatusnewResolutionopen
PlatformOSOS Version
Product Version[OCCT] 6.9.0
Target Version[OCCT] UnscheduledFixed in Version
Summary0026495: Sewing produces fictive degenerated edges
DescriptionThe attached shape is a compound of faces came from an IGES file. When one makes sewing of these faces the result shape contains degenerated edges, which are actually do not point to any singularity of the surface.

An OCCT algorithm must not produce such degenerated edges. If we need to cover a gap in 2D contours of a face it is needed to use other means than creating degenerated edges. Such fictive degenerated edges make problems in other OCCT algorithms, which assume that a degenerated edge points to a singularity in the surface.

Please see the bug #26442, in particular the comment 0026442:0043195, for an example of such algorithm.
Steps To Reproducerestore 2015-01-7108_cut.brep a

#make sewing
sewing s 1e-4 a

#count fictive degenerated edges
set nb_fictive_deg 0
foreach f [explode s f] {
if {[lsearch [dump \$f] degenerated] != -1} {
#face \$f contains degenerated edges
mksurface su \$f
foreach e [explode \$f e] {
if {[lsearch [dump \$e] degenerated] != -1} {
#edge \$e is degenerated
pcurve c2d \$e \$f
#approximate 3d curve and compute its length
approxcurveonsurf c3d c2d su
set len3d [lindex [length c3d] end]
if {\$len3d > 1e-7} {
#length of edge in 3D is not null
incr nb_fictive_deg
puts "\$e, length 3d = \$len3d"
}
}
}
}
}
if \$nb_fictive_deg {
puts "Error: sewing produced \$nb_fictive_deg fictive degenerated edges"
}
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Test case number
Attached Files 2015-01-7108_cut.brep (1,653,884 bytes) 2015-07-29 10:39

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 Issue History Date Modified Username Field Change 2015-07-29 10:39 msv New Issue 2015-07-29 10:39 msv Assigned To => gka 2015-07-29 10:39 msv File Added: 2015-01-7108_cut.brep 2015-07-29 10:40 msv Relationship added parent of 0026442 2015-07-29 10:41 msv Relationship added parent of 0026464