View Issue Details

IDProjectCategoryView StatusLast Update
0025793CommunityOCCT:Modeling Algorithmspublic2015-02-06 11:14
ReporterTimo Assigned Tobugmaster  
Status closedResolutionno change required 
Platformwin32 vc10 
Product Version6.8.0 
Target Version6.9.0 
Summary0025793: BRepAlgoAPI_Section fails when calculating the section of a face and a shell
DescriptionWhen calculating the intersection of the appended face and a trimmed shell, BRepAlgoAPI_Section fails INDEPENDENT on the order of the arguments.

The related issue 0025792 contains only the problematic face of the shell and is untrimmed. Then the correctness of the result depends on the order of the arguments.

checkshape and bopcheck do not indicate any problems. However, the problematic face is strongly bent.
Steps To Reproducerestore Turbine_VTG_Shell.brep t
explode t
bop t_1 t_2
bopsection r
whatis r
explode r
=> r contains 3 edges but should have 4 edges

bop t_2 t_1
bopsection r
whatis r
explode r
=> r contains 3 edges but should have 4 edges

TagsNo tags attached.
Test case number

Attached Files

  • Turbine_VTG_Shell.brep (435,682 bytes)
  • self-intersection.png (9,353 bytes)
  • oscillations.png (10,917 bytes)


related to 0025792 closedapn BRepAlgoAPI_Section fails depending on order of arguments 



2015-02-04 14:05


Turbine_VTG_Shell.brep (435,682 bytes)


2015-02-05 16:01

developer   ~0037129

Answer of Sergey Zaritchny:

Actually, here we have faced with improper designed surface.
Due to twisted poles in interior of the surface it has self-intersection. See the snapshot below.
It shows the zoomed-in portion of the V-iso line of the surface with parameter 0.9545.

You can see here a definite loop in the 'iso' line. In addition the surface has oscillations near the bend.
The snapshot below shows zoomed-in bending portion of the surface boundary (V-iso line with parameter 1).

The intersection algorithm cannot give a good stable result with such input geometry.
It is needed to redesign this surface so that it did not contain at least self-intersections, and at most was as smooth as possible, especially in the place where intersection with another body occurs.
Additional note. A surface should be C1-continuous. So, if you need to model a sharp bend in geometry of a body it must be modeled with an edge shared by two faces.

Unfortunately it is not possible to identify such cases by BRepCheck_Analyzer as each become apparent only inside Intersection algorithm.

Conclusion. Improper designed surface.


2015-02-05 16:01


self-intersection.png (9,353 bytes)


2015-02-05 16:01


oscillations.png (10,917 bytes)


2015-02-05 16:17

developer   ~0037132

Because the input surface is problematic, I close this issue.


2015-02-05 17:30

developer   ~0037141

Dear bugmaster, please close this bug.

Issue History

Date Modified Username Field Change
2015-02-04 14:05 Timo New Issue
2015-02-04 14:05 Timo Assigned To => msv
2015-02-04 14:05 Timo File Added: Turbine_VTG_Shell.brep
2015-02-04 14:05 Timo Issue generated from: 0025792
2015-02-04 14:05 Timo Relationship added related to 0025792
2015-02-04 15:07 Timo Description Updated
2015-02-05 16:01 Timo Note Added: 0037129
2015-02-05 16:01 Timo File Added: self-intersection.png
2015-02-05 16:01 Timo File Added: oscillations.png
2015-02-05 16:17 Timo Note Added: 0037132
2015-02-05 16:17 Timo Status new => resolved
2015-02-05 17:30 msv Note Added: 0037141
2015-02-05 17:30 msv Assigned To msv => bugmaster
2015-02-05 17:30 msv Status resolved => reviewed
2015-02-05 18:24 mkv Status reviewed => feedback
2015-02-06 11:14 bugmaster Status feedback => closed
2015-02-06 11:14 bugmaster Resolution open => no change required