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IDProjectCategoryView StatusDate SubmittedLast Update
0031947Community[OCCT] OCCT:Meshpublic2020-11-18 12:032020-11-23 11:03
Assigned Tobugmaster 
StatusclosedResolutionno change required 
PlatformWindowsOSVC++ 2013OS Version64 bit
Product Version[OCCT] 7.4.0 
Target Version[OCCT] 7.6.0*Fixed in Version 
Summary0031947: Mesh - display old brep is wrong
DescriptionI 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!
TagsNo tags attached.
Test case number
Attached Filespng file icon occ7.3_7.4.png (85,631 bytes) 2020-11-18 12:03
? file icon 7.4.brep (1,000,413 bytes) 2020-11-18 12:04

- Relationships

-  Notes
kgv (developer)
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?
xuweibin (reporter)
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!
oan (developer)
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
vsetdispmode 1
vdefaults -autoTriang 0

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 :
#On Shape faulty_2 :
#On Shape faulty_3 :
#On Shape faulty_4 :
#On Shape faulty_5 :
#Shape faulty_1 on shape faulty_5 :
#Shape faulty_2 on shape faulty_5 :
#Shape faulty_3 on shape faulty_5 :
#Shape faulty_4 on shape faulty_5 :
#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
vsetdispmode 1
vdisplay a

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

Good luck!
xuweibin (reporter)
2020-11-19 04:29

thank you
when I fixshape,my question is sloved
kgv (developer)
2020-11-19 09:58

Dear bugmaster, please close the issue.

- Issue History
Date Modified Username Field Change
2020-11-18 12:03 xuweibin New Issue
2020-11-18 12:03 xuweibin Assigned To => kgv
2020-11-18 12:03 xuweibin File Added: occ7.3_7.4.png
2020-11-18 12:04 xuweibin File Added: 7.4.brep
2020-11-18 12:09 kgv Assigned To kgv => oan
2020-11-18 12:09 kgv Severity major => minor
2020-11-18 12:09 kgv Category OCCT:Visualization => OCCT:Mesh
2020-11-18 12:09 kgv Product Version => 7.5.0
2020-11-18 12:09 kgv Summary display old brep is wrong => Mesh - display old brep is wrong
2020-11-18 12:11 kgv Note Added: 0096877
2020-11-18 12:22 xuweibin Note Added: 0096879
2020-11-18 12:34 kgv Product Version 7.5.0 => 7.4.0
2020-11-18 12:34 kgv Target Version => 7.6.0*
2020-11-18 13:42 oan Note Added: 0096882
2020-11-19 04:29 xuweibin Note Added: 0096889
2020-11-19 09:58 kgv Note Added: 0096890
2020-11-19 09:58 kgv Assigned To oan => bugmaster
2020-11-19 09:58 kgv Status new => feedback
2020-11-19 09:58 kgv Resolution open => no change required
2020-11-23 11:03 bugmaster Status feedback => closed

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