0025586: Mesh - Poor mesh quality, or failure of meshing for closed extruded surfaces with holes

(0035300)
Istvan Csanady (developer)
2014-12-11 10:19

I have attached an image of the result mesh. It should be a cylinder, with a hole.

(0035302)
msv (developer)
2014-12-11 10:45

Oleg, please look at this problem when you have time.

(0035399)
Istvan Csanady (developer)
2014-12-15 09:35

I have tested this with the current main branch, and the problem still exists. I tested it with 3rd party data (just to be sure, that the problem is not in my code), and I successfully reproduced it. See the attached STEP file.
It seems, that not only extruded faces are involved, but all faces that are closed in one direction.

Steps to reproduce:

pload all
ReadStep d tmp.stp
XGetOneShape shape d
vinit
vdisplay shape

(0035400)
Istvan Csanady (developer)
2014-12-15 10:21

I have attached a wrong stp file, but the bug can be reproduced with the attached brep files.

(0069125)
mkv (tester)
2017-08-04 18:24

Problem described in issue is reproduced on current state of OCCT.

(0086908)
oan (developer)
2019-09-06 18:22

Dear Andrey,

Attached shapes contain narrow notched tail in parametric space which cannot be processed by triangulator correctly and lead to degenerative triangles that are forbidden by BRepMesh (circle_extrusion_2d.png).

I consider it as inconsistency of the models which should be fixed by shape healing tool first.

Could you please check shapes and move this issue to shape healing category or make a decision about further plans?

(0086909)
oan (developer)
2019-09-06 18:26

bopargcheck reports inconsistencies, e.g.:

bopargcheck a #F
Made faulty shape: s1si_1
Faulties for FIRST shape found : 1
---------------------------------
Shapes are not suppotrted by BOP: NO
Self-Intersections : YES Cases(1) Total shapes(2)
Check for SI has been aborted : NO
Too small edges : NO
Bad faces : NO
Too close vertices : DISABLED
Too close edges : DISABLED
Shapes with Continuity C0 : NO
Invalid Curve on Surface : NO

Faulties for SECOND shape found : 0

Issue History
Date Modified	Username	Field	Change
2014-12-10 13:11	Istvan Csanady	New Issue
2014-12-10 13:11	Istvan Csanady	Assigned To	=> msv
2014-12-10 13:11	Istvan Csanady	File Added: meshing_failures.zip
2014-12-11 10:19	Istvan Csanady	File Added: IMG_0090.PNG
2014-12-11 10:19	Istvan Csanady	Note Added: 0035300
2014-12-11 10:22	Istvan Csanady	File Added: IMG_0091.PNG
2014-12-11 10:44	msv	Assigned To	msv => oan
2014-12-11 10:45	msv	Note Added: 0035302
2014-12-15 09:29	Istvan Csanady	File Added: tmp.stp
2014-12-15 09:35	Istvan Csanady	Note Added: 0035399
2014-12-15 10:21	Istvan Csanady	Note Added: 0035400
2015-04-21 06:10	abv	Target Version	6.9.0 => 7.1.0
2015-05-25 12:05	msv	Category	OCCT:Modeling Algorithms => OCCT:Mesh
2016-04-05 14:31	oan	Relationship added	related to 0024084
2016-10-26 18:11	oan	Target Version	7.1.0 => 7.2.0
2017-07-20 12:43	oan	Target Version	7.2.0 => 7.3.0
2017-08-04 18:24	mkv	Test case number	=> bugs mesh bug25586_1, bug25586_2, bug25586_3
2017-08-04 18:24	mkv	Note Added: 0069125
2018-02-25 21:09	abv	Target Version	7.3.0 => 7.4.0
2019-09-04 17:55	kgv	Summary	Poor mesh quality, or failure of meshing for closed extruded surfaces with holes => Mesh - Poor mesh quality, or failure of meshing for closed extruded surfaces with holes
2019-09-06 18:12	oan	File Added: circle_extrusion_2d.png
2019-09-06 18:22	oan	Note Added: 0086908
2019-09-06 18:22	oan	Assigned To	oan => abv
2019-09-06 18:22	oan	Status	new => feedback
2019-09-06 18:26	oan	Note Added: 0086909
2019-09-06 18:37	abv	Target Version	7.4.0 => 7.5.0*

Notes
(0035300) Istvan Csanady (developer) 2014-12-11 10:19	I have attached an image of the result mesh. It should be a cylinder, with a hole.

(0035302) msv (developer) 2014-12-11 10:45	Oleg, please look at this problem when you have time.

(0035399) Istvan Csanady (developer) 2014-12-15 09:35	I have tested this with the current main branch, and the problem still exists. I tested it with 3rd party data (just to be sure, that the problem is not in my code), and I successfully reproduced it. See the attached STEP file. It seems, that not only extruded faces are involved, but all faces that are closed in one direction. Steps to reproduce: pload all ReadStep d tmp.stp XGetOneShape shape d vinit vdisplay shape

(0035400) Istvan Csanady (developer) 2014-12-15 10:21	I have attached a wrong stp file, but the bug can be reproduced with the attached brep files.

(0069125) mkv (tester) 2017-08-04 18:24	Problem described in issue is reproduced on current state of OCCT.

(0086908) oan (developer) 2019-09-06 18:22	Dear Andrey, Attached shapes contain narrow notched tail in parametric space which cannot be processed by triangulator correctly and lead to degenerative triangles that are forbidden by BRepMesh (circle_extrusion_2d.png). I consider it as inconsistency of the models which should be fixed by shape healing tool first. Could you please check shapes and move this issue to shape healing category or make a decision about further plans?

(0086909) oan (developer) 2019-09-06 18:26	bopargcheck reports inconsistencies, e.g.: bopargcheck a #F Made faulty shape: s1si_1 Faulties for FIRST shape found : 1 --------------------------------- Shapes are not suppotrted by BOP: NO Self-Intersections : YES Cases(1) Total shapes(2) Check for SI has been aborted : NO Too small edges : NO Bad faces : NO Too close vertices : DISABLED Too close edges : DISABLED Shapes with Continuity C0 : NO Invalid Curve on Surface : NO Faulties for SECOND shape found : 0