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IDProjectCategoryView StatusLast Update
0023837Open CASCADEOCCT:Meshpublic2019-09-06 16:18
Reporteroan Assigned Tooan  
Status newResolutionopen 
Target VersionUnscheduled 
Summary0023837: BRepMesh shouldn't trust the SameParameter flag
DescriptionDescription of this bug is taken from issue 0023184 (post by MSV):

The check of cross-face errors should not be eliminated. It is well defined (see MeshTest_CheckTopology.hxx):

//! - cross face errors. It is a situation when a point on a common
//! boundary between two faces has different 3d coordinates on each
//! triangulation. The error is reported if the distance is greater
//! than a deflection written in triangulations.

I would change this definition, in order to compare distance between nodes of triangulation with the real distance between curves representations (value returned by the DRAW command computetolerance), rather than with mesh deflection.

As applied to this problem, we checked with OAN and found out that the common edges in the shape have improper samerange/sameparameter flag, because the command computetolerance returns the value about 0.02, while the edge's tolerance is 2e-5. BRepMesh trusts the flag SameParameter, and when a new point is inserted in some polygon on triangulation, its insertion into another polygon with the same parameter gives wrong point.

So, the solution would be to stop trusting the SameParameter flag (recompute the flag locally).
Steps To Reproducemesh standard_incmesh W7
TagsNo tags attached.
Test case number


related to 0023184 closedoan Community Bad face tessellation result 
related to 0025134 assignedmsv Open CASCADE Extended mode for checkshape command 
related to 0026106 closedbugmaster Open CASCADE BRepMesh - revision of data model 


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Issue History

Date Modified Username Field Change
2013-03-19 15:49 oan New Issue
2013-03-19 15:49 oan Assigned To => oan
2013-03-19 15:49 oan Relationship added related to 0023184
2016-10-17 11:31 oan Relationship added related to 0026106
2018-10-15 17:03 oan Relationship added related to 0025134
2019-09-06 16:18 oan Target Version => Unscheduled