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Fix erroneous calculation of segments by circle count in shape_poly_set.cpp Inflate method.

This commit is contained in:
jean-pierre charras 2016-01-14 12:37:09 +01:00
parent 5af18e553c
commit 731f785256
1 changed files with 27 additions and 1 deletions
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28
common/geometry/shape_poly_set.cpp
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@ -302,6 +302,12 @@ void SHAPE_POLY_SET::BooleanIntersection( const SHAPE_POLY_SET& a, const SHAPE_P
void SHAPE_POLY_SET::Inflate( int aFactor, int aCircleSegmentsCount )
{
// A static table to avoid repetitive calculations of the coefficient
// 1.0 - cos( M_PI/aCircleSegmentsCount)
// aCircleSegmentsCount is most of time <= 64 and usually 8, 12, 16, 32
#define SEG_CNT_MAX 64
static double arc_tolerance_factor[SEG_CNT_MAX+1];
ClipperOffset c;
BOOST_FOREACH( const POLYGON& poly, m_polys )
@ -312,7 +318,27 @@ void SHAPE_POLY_SET::Inflate( int aFactor, int aCircleSegmentsCount )
PolyTree solution;
c.ArcTolerance = fabs( (double) aFactor ) / M_PI / aCircleSegmentsCount;
// Calculate the arc tolerance (arc error) from the seg count by circle.
// the seg count is nn = M_PI / acos(1.0 - c.ArcTolerance / abs(aFactor))
// see:
// www.angusj.com/delphi/clipper/documentation/Docs/Units/ClipperLib/Classes/ClipperOffset/Properties/ArcTolerance.htm
if( aCircleSegmentsCount < 6 ) // avoid incorrect aCircleSegmentsCount values
aCircleSegmentsCount = 6;
double coeff;
if( aCircleSegmentsCount > SEG_CNT_MAX || arc_tolerance_factor[aCircleSegmentsCount] == 0 )
{
coeff = 1.0 - cos( M_PI/aCircleSegmentsCount);
if( aCircleSegmentsCount <= SEG_CNT_MAX )
arc_tolerance_factor[aCircleSegmentsCount] = coeff;
}
else
coeff = arc_tolerance_factor[aCircleSegmentsCount];
c.ArcTolerance = std::abs( aFactor ) * coeff;
c.Execute( solution, aFactor );