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IDProjectCategoryView StatusDate SubmittedLast Update
0026740Open CASCADE[OCCT] OCCT:Modeling Algorithmspublic2015-10-01 15:572019-09-04 12:11
Assigned Tomsv 
PlatformOSOS Version
Product Version 
Target Version[OCCT] UnscheduledFixed in Version 
Summary0026740: Modeling Algorithms - Incorrect result of blend operation in "blend simple X4" test case
DescriptionTheoretically, curve l must tangent line AB in point C (see master_result.png attached picture). Therefore, it is necessary for resulting shape to have a vertex in point C in order to be valid. This vertex is absence.

More over, if we insert this vertex in the place C then the part of the current result from A to C must be absence (i.e. the filet must be made for red highlighted edge in source_shape.png file only).
Steps To Reproducetest blend simple X4
TagsNo tags attached.
Test case number
Attached Filespng file icon master_result.png (17,059 bytes) 2015-10-01 15:57
png file icon source_shape.PNG (31,930 bytes) 2015-10-01 15:58

- Relationships
related to 0026675closedbugmaster Open CASCADE Eliminate normalization of coordinates in ApproxInt package 
related to 0026907assignedjgv Open CASCADE ChFi3d_Builder algorithm uses old Boolean operations: wrong processing of shapes with seam and degenerated edges 
related to 0028575assignedemv Open CASCADE Removal of the old Boolean Operations algorithm - BRepAlgo_BooleanOperation 
related to 0026655newmsv Open CASCADE ChFi3d_Builder algorithm fails to build fillets if some input edges connect with seam edges 

-  Notes
nbv (developer)
2015-10-01 16:14

A few words about validity the result in terms of BRepCheck algorithm.

Draw[]> explode result f
Draw[]> explode result_3 e
Draw[]> xdistef result_3_5 result_3
#Max distance = 0.0025028007416767954

Edge rr_3_5 is not valid in terms of same-parameter (it is valid in terms of BRepCheck algorithm because it has big tolerance). I.e. its 2D- and 3D-curve are not matched each other. As result, 2D-curve of result_3_5 does not tangent rr_3_2 edge (despite it must do it).

Consequently, the validity of the result is pure chance.

I tried to make more precise filet-edge with change some parameters of IntWalk_PWalking algorithm (function ChFi3d_ComputeCurves(...), line "IntWalk_PWalking IntKK(S1,S2,tol3d,tol3d,fleche,Step)"). As result, I obtained an edge with maximal distance between 2D- and 3D-curve approximately 1.0e-13. After that, BRepCheck algorithm returns "BRepCheck_SelfIntersectingWire". The main reason is the vertex is absence (see bug description).
nbv (developer)
2015-10-01 18:25
edited on: 2015-10-01 18:26

Other remarks.

1. Firstly, the intersection edge (result_3_5 in previous message) is found as result of GeomInt_IntSS algorithm between two cylinders. It returns two intersection line, which are connected in point C. However, ChFi3d_Builder does not apply it to make fillet. Therefore, it rebuilds intersection line with IntWalk_PWalking algorithm and obtains single line as result.

2. If we insert this vertex in the place C then we will obtain filleted face between C and B only (see master_result.png and bug description). For obtaining result shown in the picture master_result.png we should add another edge to the arguments of "blend" DRAW-command. On the current MASTER this operation leads to exception.

nbv (developer)
2015-10-02 09:32

I have checked described situation on OCCT 6.7.0 and have obtained as same as result.

- Issue History
Date Modified Username Field Change
2015-10-01 15:57 nbv New Issue
2015-10-01 15:57 nbv Assigned To => msv
2015-10-01 15:57 nbv File Added: master_result.png
2015-10-01 15:57 nbv Assigned To msv => nbv
2015-10-01 15:58 nbv File Added: source_shape.PNG
2015-10-01 16:14 nbv Note Added: 0046377
2015-10-01 16:16 nbv Relationship added related to 0026675
2015-10-01 18:01 msv Status new => assigned
2015-10-01 18:25 nbv Note Added: 0046385
2015-10-01 18:26 nbv Note Edited: 0046385 View Revisions
2015-10-02 09:32 nbv Note Added: 0046387
2016-10-25 19:04 msv Target Version 7.1.0 => 7.2.0
2017-06-15 11:06 nbv Relationship added related to 0026907
2017-06-15 11:06 nbv Relationship deleted related to 0026907
2017-06-15 11:06 nbv Relationship added related to 0026655
2017-07-21 11:04 msv Target Version 7.2.0 => 7.3.0
2017-12-05 17:09 msv Target Version 7.3.0 => 7.4.0
2017-12-08 11:57 nbv Relationship added related to 0029359
2018-03-05 10:52 nbv Relationship added related to 0026907
2018-03-05 10:52 nbv Relationship added related to 0028575
2019-08-12 19:08 msv Assigned To nbv => msv
2019-08-12 19:13 msv Target Version 7.4.0 => Unscheduled
2019-09-04 12:11 kgv Summary Incorrect result of blend operation in "blend simple X4" test case => Modeling Algorithms - Incorrect result of blend operation in "blend simple X4" test case

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