0029745: GeomAdaptor_Surface::VIntervals fails on periodic surfaces

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Date Submitted

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0029745

Community

[OCCT] OCCT:Modeling Data

public

2018-05-08 17:55

Reporter

ventu

Assigned To

msv

Priority

normal

Severity

crash

Status

new

Resolution

open

Platform

OS Version

Product Version

[OCCT] 7.2.0

Target Version

Fixed in Version

Summary

0029745: GeomAdaptor_Surface::VIntervals fails on periodic surfaces

Description

Suppose:
_ we have a V periodic NURBS Surface;
_ we have a GeomAdaptor_Surface with V limits outside of the period;
_ the surface has discontinuities;
_ we call GeomAdaptor_Surface::VIntervals to get a list of continuous subintervals.

That method will build an U iso-curve and get such intervals on that; at the end, however, that intervals are bounded with:
  T(T.Lower()) = myVFirst;
  T(T.Lower() + myNbVIntervals) = myVLast;

The problem arises since the value returned by the curve Intervals(...) method will be within the period, so those values will be invalid.

Example:
_ surface with periodic V knot vector ranging [0 ; 4];
_ surface adaptor with limits [5 ; 6].
_ Intervals(...) on the ISO curve returns [1,2,3];
_ the statements reported above will transform the result in [5,2,6].

This will lead to a crash in subsequent processing.

A solution along the line of the following might work:
  if (mySurface->IsVPeriodic())
    for (Standard_Integer i=T.Lower()+1;i<T.Lower()+myNbVIntervals;++i)
      T(i)+=myVFirst-T(T.Lower());
  T(T.Lower()) = myVFirst;
  T(T.Lower() + myNbVIntervals) = myVLast;

Notice the problem should also occur in U direction.

Issue History
Date Modified	Username	Field	Change
2018-05-08 17:55	ventu	New Issue
2018-05-08 17:55	ventu	Assigned To	=> msv

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