View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0024127 | Community | OCCT:Mesh | public | 2013-08-26 16:01 | 2014-11-11 13:01 |
| Reporter | Vitezslav Zajic | Assigned To | bugmaster | ||
| Priority | normal | Severity | minor | ||
| Status | closed | Resolution | fixed | ||
| Product Version | 6.6.0 | ||||
| Target Version | 6.8.0 | Fixed in Version | 6.8.0 | ||
| Summary | 0024127: Mesh generated with BRepMesh_FastDiscret does not reflect a deflection setting | ||||
| Description | In some cases, edges in triangulation generated by BRepMesh_FastDiscret can have much grater deflection from the curves they should approximate than is specified. This is due to the computation of the deflection in function splitSegment in file BRepMesh_FastDiscret.cxx. This function takes only one(!) sample point in the middle of the source curve and computes its distance from the segment. If this is lesser than the specified deflection, it considers the segment as a good approximation of the curve, even if it otherwise curves quite far from the segment. One such example is shown in an attachment. When a surface shown in file surface.png is meshed with BRepMesh_FastDiscret, deflection set to 1.0, the generated mesh has only two triangles and very poorly approximates the one non-straight curve, the deflection of the approximating edge from the curve is greater than 2.5 (see surface_with_bad_triangulation.png). When a splitSegment method is alter in an easy way such that it takes several evenly spaced sample points, the generated mesh is OK, as is illustrated in file right_triangulation.png. For easier reproducibility, I have also attached a simple test application that creates the above mentioned surface and triangulates it and a patch that alters the splitSegment function. I hope that I'm not missing something, the documentation of meshing algorithms is quite poor (I definitely vote for feature 0024117). | ||||
| Steps To Reproduce | You can compile and run attached wrong_triangulation.cpp to reproduce the bug. Draw script reproducing the problem: bsplinesurf s 2 4 0.0 3 0.34 1 0.67 1 1.0 3 1 2 0.0 2 1.0 2 10 0 0 1 6 0 0 1 4 0 0 1 2 0 0 1 0 0 0 1 10 5 0 1 6 5 0 1 4 5 0 1 1.5 9 0 1 0 5 0 1 mkface f s incmesh f 1 trinfo f #This shape contains 2 triangles. # 4 nodes. #Maximal deflection 0.65883450744480032 | ||||
| Tags | No tags attached. | ||||
| Test case number | bugs mesh(016) bug24127 | ||||
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triangulation.zip (82,873 bytes) |
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Dear Bugmaster, please create corresponding test case and check that current behavior of BRepMesh is correct and produces appropriate mesh. Note that behavior should be checked using fix for issue 0024959. |
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Looks Ok on current master (90 triangles) |
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Branch CR24127 has been created by mkv. SHA-1: b1721cb348ed97574a2e3ac3e3ab17467d586aef Detailed log of new commits: Author: mkv Date: Wed Oct 8 20:05:06 2014 +0400 0024127: Mesh generated with BRepMesh_FastDiscret does not reflect a deflection setting \n Test case for issue CR24127 |
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Dear BugMaster, Test cases bugs/mesh(016)/bug24127 is created and pushed to new branch CR24127 of occt git-repository. Test cases bugs/mesh(016)/bug24127 is OK. |
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Branch CR24127 has been deleted by inv. SHA-1: b1721cb348ed97574a2e3ac3e3ab17467d586aef |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2013-08-26 16:01 | Vitezslav Zajic | New Issue | |
| 2013-08-26 16:01 | Vitezslav Zajic | Assigned To | => oan |
| 2013-08-26 16:01 | Vitezslav Zajic | File Added: triangulation.zip | |
| 2014-05-21 13:10 |
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Assigned To | oan => azn |
| 2014-05-21 13:10 |
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Status | new => assigned |
| 2014-05-21 13:10 |
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Target Version | => 6.8.0 |
| 2014-05-26 12:57 | oan | Steps to Reproduce Updated | |
| 2014-05-26 15:17 | oan | Relationship added | related to 0024959 |
| 2014-09-26 12:09 |
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Assigned To | azn => oan |
| 2014-09-26 15:58 | oan | Assigned To | oan => bugmaster |
| 2014-09-26 15:58 | oan | Note Added: 0032249 | |
| 2014-09-26 17:11 |
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Note Added: 0032263 | |
| 2014-09-26 17:11 |
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Status | assigned => feedback |
| 2014-09-29 15:47 | bugmaster | Assigned To | bugmaster => mkv |
| 2014-10-08 20:05 | git | Note Added: 0032843 | |
| 2014-10-08 20:28 |
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Note Added: 0032846 | |
| 2014-10-08 20:28 |
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Assigned To | mkv => bugmaster |
| 2014-10-08 20:28 |
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Status | feedback => tested |
| 2014-10-08 20:29 |
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Test case number | => bugs mesh(016) bug24127 |
| 2014-10-13 17:52 | bugmaster | Changeset attached | => occt master 432a8df0 |
| 2014-10-13 17:52 | bugmaster | Status | tested => verified |
| 2014-10-13 17:52 | bugmaster | Resolution | open => fixed |
| 2014-10-21 16:42 | git | Note Added: 0033421 | |
| 2014-11-11 12:43 |
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Fixed in Version | => 6.8.0 |
| 2014-11-11 13:01 |
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Status | verified => closed |
