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IDProjectCategoryView StatusLast Update
0029060Open CASCADEOCCT:Modeling Algorithmspublic2023-08-01 15:08
ReportermsvAssigned Tomsv 
Status assignedResolutionopen 
Product Version7.2.0 
Target VersionUnscheduled 
Summary0029060: BRepOffset_MakeOffset produces invalid shape in test bugs modalg_7 bug28131
DescriptionStandard offset algorithm BRepOffset_MakeOffset produces invalid shape in test bugs modalg_7 bug28131 (see 0028131). The current version of the test calls fixshape to fix the result shape, and this leads to increasing of the tolerance.
It is needed to investigate why the result is invalid.
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Test case number

Attached Files

  • surf_and_offset.png (41,481 bytes)


related to 0028131 closedbugmaster Community BRepOffset_MakeOffset can't create offset with a face which created by filling 3 bsplinecurve 



2017-09-15 12:15

developer   ~0070578

Investigation revealed that the input b-spline surface has such properties near the degeneracy that its offset has "corrupted" degeneracy. Please see the attached snapshot surf_and_offset.png. The degeneracy point is shifted from the corner of the surface along one of boundary to the inside. At this, the place between the corner and degeneracy behaves like a "black hole" - there is difficult to find a parameters (u,v) to hit into this area.
The offset algorithm creates an edge to cover this part of boundary, and this edge is not degenerated. However, the correspondence of 3D curve and p-curve cannot be fulfilled, and the edge is reported to have invalid curve on surface.

In the scope of this issue it is needed to modify the offset algorithm so that to provide setting to the edge the enough tolerance to cover the same-parameter error.


2017-09-15 12:15


surf_and_offset.png (41,481 bytes)

Issue History

Date Modified Username Field Change
2017-08-28 10:14 msv New Issue
2017-08-28 10:14 msv Assigned To => msv
2017-08-28 10:14 msv Status new => assigned
2017-08-28 10:14 msv Relationship added related to 0028131
2017-08-28 10:27 msv Summary BRepOffset_MakeOffset produces invalid shape in test bugs modalg bug28131 => BRepOffset_MakeOffset produces invalid shape in test bugs modalg_7 bug28131
2017-08-28 10:27 msv Description Updated
2017-09-15 12:15 msv Note Added: 0070578
2017-09-15 12:15 msv File Added: surf_and_offset.png
2019-08-12 16:43 msv Target Version 7.4.0 => 7.5.0
2020-09-14 22:55 msv Target Version 7.5.0 => 7.6.0
2021-08-29 18:52 msv Target Version 7.6.0 => 7.7.0
2022-10-24 10:42 szy Target Version 7.7.0 => 7.8.0
2023-08-01 15:08 dpasukhi Target Version 7.8.0 => Unscheduled