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0031947Community[OCCT] OCCT:Meshpublic2020-11-18 12:032020-11-23 11:03
xuweibin 
bugmaster 
normalminor 
closedno change required 
WindowsVC++ 201364 bit
[OCCT] 7.4.0 
[OCCT] 7.6.0* 
0031947: Mesh - display old brep is wrong
I save a topo_shape to brep file with occ7.3.
I upgrade occ to version 7.5,I found a strange thing.
I read and display the old brep file,the result is not what I want!
No tags attached.
png occ7.3_7.4.png (85,631) 2020-11-18 12:03
https://tracker.dev.opencascade.org/
? 7.4.brep (1,000,413) 2020-11-18 12:04
https://tracker.dev.opencascade.org/
Issue History
2020-11-18 12:03xuweibinNew Issue
2020-11-18 12:03xuweibinAssigned To => kgv
2020-11-18 12:03xuweibinFile Added: occ7.3_7.4.png
2020-11-18 12:04xuweibinFile Added: 7.4.brep
2020-11-18 12:09kgvAssigned Tokgv => oan
2020-11-18 12:09kgvSeveritymajor => minor
2020-11-18 12:09kgvCategoryOCCT:Visualization => OCCT:Mesh
2020-11-18 12:09kgvProduct Version => 7.5.0
2020-11-18 12:09kgvSummarydisplay old brep is wrong => Mesh - display old brep is wrong
2020-11-18 12:11kgvNote Added: 0096877
2020-11-18 12:22xuweibinNote Added: 0096879
2020-11-18 12:34kgvProduct Version7.5.0 => 7.4.0
2020-11-18 12:34kgvTarget Version => 7.6.0*
2020-11-18 13:42oanNote Added: 0096882
2020-11-19 04:29xuweibinNote Added: 0096889
2020-11-19 09:58kgvNote Added: 0096890
2020-11-19 09:58kgvAssigned Tooan => bugmaster
2020-11-19 09:58kgvStatusnew => feedback
2020-11-19 09:58kgvResolutionopen => no change required
2020-11-23 11:03bugmasterStatusfeedback => closed

Notes
(0096877)
kgv   
2020-11-18 12:11   
> I upgrade occ to version 7.5,I found a strange thing.
You description points to OCCT 7.3.0 vs OCCT 7.5.0, but your screenshot mentions OCCT 7.4.0. Which version you have actually tried?
(0096879)
xuweibin   
2020-11-18 12:22   
I both tried,last year I upgrade to occ7.4,I found this problem.
When occ7.5 is released,I tried again, the problem exist!
(0096882)
oan   
2020-11-18 13:42   
Hello xuweibin,

attached shape already contains triangulation computed and stored by elder version of OCCT and it seems incorrect anyway. It is possible to check it like this:

pload ALL
restore 7.4.brep a
vinit
vsetdispmode 1
vdefaults -autoTriang 0
vdisplay
vfit

This means that described problem is not in version 7.5.0, but common since the version you used to create aforementioned shape.

Moreover, shape itself is invalid according to the report of checkshape:

pload ALL
restore 7.4.brep a
tclean a
checkshape a

#On Shape faulty_1 :
#BRepCheck_No3DCurve
#On Shape faulty_2 :
#BRepCheck_No3DCurve
#On Shape faulty_3 :
#BRepCheck_No3DCurve
#On Shape faulty_4 :
#BRepCheck_No3DCurve
#On Shape faulty_5 :
#BRepCheck_UnorientableShape
#Shape faulty_1 on shape faulty_5 :
#BRepCheck_NoCurveOnSurface
#Shape faulty_2 on shape faulty_5 :
#BRepCheck_NoCurveOnSurface
#Shape faulty_3 on shape faulty_5 :
#BRepCheck_NoCurveOnSurface
#Shape faulty_4 on shape faulty_5 :
#BRepCheck_NoCurveOnSurface
#
#Faulty shapes in variables faulty_1 to faulty_5


Summarizing all from the above, BRepMesh is expected to build correct triangulation given that target shape contains no drastic deviations regarding shape validity. In the reported case shape does not contain either 3D curve or curve on surface. This could be considered as significant failure due to the fact that this data is required and triangulation is built upon it.

If you try to fix the model as follows, it will look as you expected:

pload ALL
restore 7.4.brep a
tclean a
fixshape a a
vinit
vsetdispmode 1
vdisplay a
vfit

Another approach it to try to redesign initial model so it would be valid by default.

Good luck!
(0096889)
xuweibin   
2020-11-19 04:29   
thank you
when I fixshape,my question is sloved
(0096890)
kgv   
2020-11-19 09:58   
Dear bugmaster, please close the issue.