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|ID||Project||Category||View Status||Date Submitted||Last Update|
|0023820||Community||[OCCT] OCCT:Modeling Algorithms||public||2013-03-07 14:46||2017-12-05 17:09|
|Product Version||[OCCT] 6.5.4|
|Target Version||[OCCT] 7.4.0*||Fixed in Version|
|Summary||0023820: Wrong result of projection algorithm when a polygon geometry is projected on a set of multiple faces|
|Description||Wrong result of projection algorithm ["BrepAlgo_NormalProjection” and “ProjLib_CompProjectedCurve”] when a polygon geometry is projected on a set of multiple faces [TopoDS_Compound of the multiple TopoDS_Face]. |
The polygon geometry is given by set of ordered points in 3D space. It is required to find the projection of this polygon on to the given set of connected faces in normal direction.
Edges are constructed using the points of polygon and BrepAlgo_NormalProjection is used to project on the TopoDS_Compound of the multiple TopoDS_Face entities.
Internally, ProjLib_CompProjectedCurve::Init() is called, in which the step size for identifying the projection points in the edges is constant. Because of this some of the smaller faces in the TopoDS_Compound get missed out.
The fix for the defect is proposed to use the parametric space of the edges for identifying the step size.
|Steps To Reproduce||Please rfer the uploaded document NormalProjection_Defect.pdf|
|Tags||No tags attached.|
|Test case number|
|Attached Files|| NormalProjection_Defect.pdf (246,941 bytes) 2013-03-07 14:48|
NormalProjection_DefectTestSourceCode.zip (187,206 bytes) 2013-03-07 16:10
|code committed to brnach CR23820. Branch pushed to remote repo.|
Concerning your contribution on the isssue 23820:
1. Why do you think that the value of <SearchStep> depending on first derivative of curve in its first point is better than current one? In your version I see:
SearchStep = Min(10*MinStep, 0.1/VD1);
I think that you really mean 0.1*VD1, not 0.1/VD1. But nevertheless, the step is also constant along the curve and can become too small if the derivative in first point is small.
2. The approach for avoiding of undesirable results by "try-catch" is not good in the loop of iterations: it is better to analyze the reasons of failure and do something depending on the situation, without call of methods leading to exceptions. It also applies to your changes in BRepAlgo_NormalProjection.cxx.
Please find my response below:
1. The steps 0.01 and 0.1 are arbitrary
2. If the line segment is long, then it is possible that containment will be missed (as it happens here).
3. If we consider the parametric distance covered and relate it to the tangent length.
u' = u + delta(u)
delta(u) is chosen here per unit length in object space (some factor: 0.1/0.01)/ (dc/du).
Of course, this is also not correct way as well, the better way is to
1. Find extrema (Use ExtremaDS)
2. Use extreme points (inside/outside) as a start point to create curve segments.
What do you suggest?
I agree with you on try-catch. It should be analyzed further. I will request you not to consider it.
|2013-03-07 14:46||sneeraj||New Issue|
|2013-03-07 14:46||sneeraj||Assigned To||=> jgv|
|2013-03-07 14:48||sneeraj||Priority||normal => high|
|2013-03-07 14:48||sneeraj||Severity||minor => major|
|2013-03-07 14:48||sneeraj||Reproducibility||have not tried => always|
|2013-03-07 14:48||sneeraj||Product Version||=> 6.5.4|
|2013-03-07 14:48||sneeraj||Target Version||=> 6.6.0|
|2013-03-07 14:48||sneeraj||Description Updated||View Revisions|
|2013-03-07 14:48||sneeraj||Steps to Reproduce Updated||View Revisions|
|2013-03-07 14:48||sneeraj||File Added: NormalProjection_Defect.pdf|
|2013-03-07 16:10||sneeraj||File Added: NormalProjection_DefectTestSourceCode.zip|
|2013-03-07 16:17||sneeraj||Assigned To||jgv => sneeraj|
|2013-03-07 19:23||sneeraj||Note Added: 0023635|
|2013-03-07 19:23||sneeraj||Status||new => resolved|
|2013-03-07 19:28||sneeraj||Note Added: 0023636|
|2013-03-07 19:30||sneeraj||Assigned To||sneeraj => jgv|
|2013-03-12 17:13||jgv||Note Added: 0023682|
|2013-03-12 17:13||jgv||Status||resolved => assigned|
|2013-03-12 17:14||jgv||Assigned To||jgv => sneeraj|
|2013-03-18 20:04||sneeraj||Note Added: 0023785|
|2013-03-18 20:04||sneeraj||Assigned To||sneeraj =>|
|2013-03-18 20:05||sneeraj||Assigned To||=> jgv|
|2013-04-19 16:19||abv||Assigned To||jgv => ifv|
|2013-04-19 16:19||abv||Target Version||6.6.0 => 6.7.0|
|2013-12-21 10:21||abv||Target Version||6.7.0 => 6.7.1|
|2014-04-04 18:19||abv||Target Version||6.7.1 => 6.8.0|
|2014-09-26 10:29||abv||Target Version||6.8.0 => 7.1.0|
|2016-10-28 11:54||msv||Target Version||7.1.0 => 7.2.0|
|2017-07-21 11:34||msv||Target Version||7.2.0 => 7.3.0|
|2017-12-05 17:09||msv||Target Version||7.3.0 => 7.4.0*|
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