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0024185Community[OCCT] OCCT:Modeling Algorithmspublic2013-09-17 14:432018-08-28 11:35
Vitezslav Zajic 
WindowsVC++ 201032 bit
[OCCT] 6.6.0 
bugs modalg_7 bug24185
0024185: Wrong projection of a wire to a face
OpenCascade gives a wrong projection of the wire to the face1 (see attached files). The wire was constructed as an intersection between face1 and face2 and then smoothed by Approx_Curve3d. Both faces are attached, so you can compare the wire to the intersection of the faces yourself.
Draw script:

restore face1.brep f1
restore wire.brep w
nproject r w f1

You can compare the wire in wire.brep to the intersection of the two faces:

restore face2.brep f2
section s f1 f2
No tags attached.
related to 0030090verified bugmaster Open CASCADE Modeling Algorithms - BRepLib::FindValidRange does not find valid range for the edge 
? wire.brep (10,280) 2013-09-17 14:43
? face1.brep (1,235) 2013-09-17 14:44
? face2.brep (2,600) 2013-09-17 14:44
Issue History
2013-09-17 14:43Vitezslav ZajicNew Issue
2013-09-17 14:43Vitezslav ZajicAssigned To => ifv
2013-09-17 14:43Vitezslav ZajicFile Added: wire.brep
2013-09-17 14:44Vitezslav ZajicFile Added: face1.brep
2013-09-17 14:44Vitezslav ZajicFile Added: face2.brep
2013-10-25 19:00Vitezslav ZajicNote Added: 0026292
2017-07-25 14:53apvNote Added: 0068677
2017-07-25 14:54apvTest case number => bugs modalg_7 bug24185
2017-07-25 14:57gitNote Added: 0068678
2018-08-28 11:35emvRelationship addedrelated to 0030090

Vitezslav Zajic   
2013-10-25 19:00   
The bug seems to be caused by numerical instability when approximating the projection by a bspline curve. If you increase allowed number of poles of the bspline curve and/or increase precision, the projection looks fine:

nproject r w f1 0.0005 C0 14 1000

This is not so surprising, but maybe default precision/number of poles is too large or small, respectively? Even with few poles, could the approximation be more stable?
2017-07-25 14:53   
Problem described in issue is reproduced on current state of OCCT
2017-07-25 14:57   
Branch CR24185 has been created by apv.

SHA-1: 5fb9e6a42158c6f780f0c552dc605f6181c115fb

Detailed log of new commits:

Author: apv
Date: Tue Jul 25 14:56:37 2017 +0300

    Test for 0024185: Wrong projection of a wire to a face