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IDProjectCategoryView StatusLast Update
0027924CommunityOCCT:Data Exchangepublic2021-10-18 14:02
ReporterRoman Lygin Assigned Togka  
PrioritynormalSeverityminor 
Status newResolutionopen 
Product Version7.0.0 
Target Version7.7.0 
Summary0027924: IGES importer/exporter incorrectly parametrizes pcurves on conical surface (type 194)
DescriptionIGES importer/exporter does not scale p-curves on conical surfaces as if parametrization of IGES conical surface (type 194 form 1) were equal to OCC (Geom_Conical Surface). This is not the case as in IGES the conical surface is V-parametrized by height along Z axis, not by length along generatrix (as in OCC).

See IGES 5.6 spec, par 4.52:
S(u, v) = C + ( r+ v tan(s)) (cos ( u ) x + sin( u ) y ) + v z

where for OCC:
S(u,v) = O + (R + v*sin(s)) * (cos(u)*XDir + sin(u)*YDir) + v*cos(s)*ZDir
Steps To Reproducecone c 45 0
mkface f c 0 1 10 20
param write.iges.brep.mode BRep
brepiges f
entity 15 6 (where 15 is rank number of pcurves)

Bounded Line
Line from IGESGeom
Starting Point : (0,20,0)
End Point : (0,10,0)

whereas the line must go from (0, 1.414213) to (0, 0.7071) (i.e. *cos(45degrees)).
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Issue History

Date Modified Username Field Change
2016-09-30 17:56 Roman Lygin New Issue
2016-09-30 17:56 Roman Lygin Assigned To => gka
2016-10-26 11:02 gka Target Version 7.1.0 => 7.2.0
2017-07-27 09:24 abv Target Version 7.2.0 => 7.4.0
2019-09-04 12:58 abv Target Version 7.4.0 => 7.5.0
2020-09-17 20:35 gka Target Version 7.5.0 => 7.6.0
2021-10-18 14:02 kgv Target Version 7.6.0 => 7.7.0