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IDProjectCategoryView StatusDate SubmittedLast Update
0026965Community[OCCT] OCCT:Meshpublic2015-12-08 14:092018-02-25 21:14
ReporterIstvan Csanady 
Assigned Tooan 
PlatformOSOS Version
Product Version 
Target Version[OCCT] 7.4.0*Fixed in Version 
Summary0026965: BRepMesh_IncrementalMesh hangs, and consumes infinite memory
DescriptionFor swept shapes like the attached one, BRepMesh_IncrementalMesh quite often hangs (forever) and constantly allocates more and more memory (7-30MB/sec)

These shapes are created with BRepOffsetAPI_MakePipe, by sweeping an arbitrary profile through a wavy BSpline.
Steps To Reproduce#Load the attached shape with DRAWEXE.

restore mesh_hang.brep a
tclean a
vsetdispmode 1
vdisplay a
Additional information
and documentation updates
This is probably related to 0026889
TagsNo tags attached.
Test case number
Attached Files? file icon mesh_hang.brep (338,432 bytes) 2015-12-08 14:09
png file icon elbow_1.png (54,317 bytes) 2016-02-08 15:14
png file icon elbow_2.png (86,866 bytes) 2016-02-08 15:14

- Relationships
related to 0027693assignedoan Open CASCADE BRepMesh: fine edge tessellation leads to excess number of triangles along the whole U or V stripes 
has duplicate 0026889newoan Community Very poor mesh result from shape 

-  Notes
oan (developer)
2016-02-08 15:14

Dear Istvan,

generally the problem with hanging of BRepMesh on such kind of shapes is connected with surface eversions on the elbows which can be observed on attached screenshots (elbow_1, elbow_2). BRepMesh's logic tries to produce mesh suitable for visualization, i.e. it tries to prevent occurence of dark areas which are caused by strong deviation of normals at triangle vertices. In this case it generates additional points, thus generates more finier mesh. Considering the problematic areas on elbows, algorithm could insert a lot of points in order to gain the suitable quality of a result. However, existing drastic bend can lead to unconditional division without achieving the desired result.

In order to prevent such behavior you can disable procedure of addition of new vertices at all by using -surf_def_off parameter or specify minimum size parameter in order to limit mesh amplification. E.g. the following command produces mesh without hanging:

incmesh a 0.1 -min 0.1

Best regards,
Istvan Csanady (developer)
2016-02-09 05:32

Wow, thanks Oleg, that helped! Works like a charm.
abv (manager)
2016-02-09 09:25

Oleg, can we add some default restriction against insertion of infinite number of points? I suppose this can be made either restricting number of iterations or setting some default value for this parameter "-min".
oan (developer)
2016-02-09 10:41

Andrey, yes we can. In fact, there is an issue #23513 that supposes this restriction and now it should be tested and vertified.
Istvan Csanady (developer)
2016-03-10 15:48

For me that works, it can be closed (just because the ticket is in waiting for feedback state)
abv (manager)
2016-03-10 15:57

Oleg, please consider this issue together with #23513 (as one more test case)
oan (developer)
2017-08-11 13:05

Performance could be improved by #26106 patch.

- Issue History
Date Modified Username Field Change
2015-12-08 14:09 Istvan Csanady New Issue
2015-12-08 14:09 Istvan Csanady Assigned To => oan
2015-12-08 14:09 Istvan Csanady File Added: mesh_hang.brep
2016-02-02 11:07 abv Target Version 7.0.0 => 7.1.0
2016-02-08 14:06 oan Relationship added has duplicate 0026889
2016-02-08 14:17 oan Relationship added related to 0023513
2016-02-08 15:14 oan File Added: elbow_1.png
2016-02-08 15:14 oan File Added: elbow_2.png
2016-02-08 15:14 oan Note Added: 0050481
2016-02-08 15:14 oan Assigned To oan => Istvan Csanady
2016-02-08 15:14 oan Status new => feedback
2016-02-09 05:32 Istvan Csanady Note Added: 0050504
2016-02-09 09:25 abv Note Added: 0050506
2016-02-09 10:41 oan Note Added: 0050509
2016-03-10 15:48 Istvan Csanady Note Added: 0051522
2016-03-10 15:57 abv Note Added: 0051523
2016-03-10 15:57 abv Assigned To Istvan Csanady => oan
2016-03-10 15:57 abv Status feedback => assigned
2016-10-25 17:43 oan Relationship added related to 0027693
2016-10-25 17:45 oan Target Version 7.1.0 => 7.2.0
2016-11-01 13:53 oan Relationship added related to 0026106
2017-07-20 12:43 oan Target Version 7.2.0 => 7.3.0
2017-08-11 12:59 oan Steps to Reproduce Updated View Revisions
2017-08-11 13:05 oan Note Added: 0069316
2018-02-25 21:14 abv Target Version 7.3.0 => 7.4.0*

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