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Fix issue in CalcArcCenter( VECTOR2D& aStart, VECTOR2D& aMid, VECTOR2D& aEnd ) 

It happens when the segment (aStart, aMid) is horizontal
Probably also when the segment (aEnd, aMid) is horizontal
Slopes with value 0.0 are set to double:: epsilon(), but it was a too small values
generating broken calculations.
Now set to 1e-10 (it seems working).
Fixes #16089
https://gitlab.com/kicad/code/kicad/-/issues/16089
This commit is contained in:
jean-pierre charras 2023-11-18 20:06:00 +01:00
parent 930b695b9f
commit 7fd9226bec
3 changed files with 64 additions and 8 deletions
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66
libs/kimath/src/trigo.cpp
View File

@ -37,6 +37,54 @@
#include <trigo.h>
/*
CircleCenterFrom3Points calculate the center of a circle defined by 3 points
It is similar to CalcArcCenter( const VECTOR2D& aStart, const VECTOR2D& aMid, const VECTOR2D& aEnd )
but it was needed to debug CalcArcCenter, so I keep it available for other issues in CalcArcCenter
The perpendicular bisector of the segment between two points is the
set of all points equidistant from both. So if you take the
perpendicular bisector of (x1,y1) and (x2,y2) and the perpendicular
bisector of the segment from (x2,y2) to (x3,y3) and find the
intersection of those lines, that point will be the center.
To find the equation of the perpendicular bisector of (x1,y1) to (x2,y2),
you know that it passes through the midpoint of the segment:
((x1+x2)/2,(y1+y2)/2), and if the slope of the line
connecting (x1,y1) to (x2,y2) is m, the slope of the perpendicular
bisector is -1/m. Work out the equations for the two lines, find
their intersection, and bingo! You've got the coordinates of the center.
An error should occur if the three points lie on a line, and you'll
need special code to check for the case where one of the slopes is zero.
see https://web.archive.org/web/20171223103555/http://mathforum.org/library/drmath/view/54323.html
*/
//#define USE_ALTERNATE_CENTER_ALGO
#ifdef USE_ALTERNATE_CENTER_ALGO
bool CircleCenterFrom3Points( const VECTOR2D& p1, const VECTOR2D& p2, const VECTOR2D& p3, VECTOR2D* aCenter )
{
// Move coordinate origin to p2, to simplify calculations
VECTOR2D b = p1 - p2;
VECTOR2D d = p3 - p2;
double bc = ( b.x*b.x + b.y*b.y ) / 2.0;
double cd = ( -d.x*d.x - d.y*d.y ) / 2.0;
double det = -b.x*d.y + d.x*b.y;
if( fabs(det) < 1.0e-6 ) // arbitrary limit to avoid divide by 0
return false;
det = 1/det;
aCenter->x = ( -bc*d.y - cd*b.y ) * det;
aCenter->y = ( b.x*cd + d.x*bc ) * det;
*aCenter += p2;
return true;
}
#endif
bool IsPointOnSegment( const VECTOR2I& aSegStart, const VECTOR2I& aSegEnd,
const VECTOR2I& aTestPoint )
{
@ -285,8 +333,8 @@ const VECTOR2D CalcArcCenter( const VECTOR2D& aStart, const VECTOR2D& aEnd,
const EDA_ANGLE& aAngle )
{
EDA_ANGLE angle( aAngle );
VECTOR2I start = aStart;
VECTOR2I end = aEnd;
VECTOR2D start = aStart;
VECTOR2D end = aEnd;
if( angle < ANGLE_0 )
{
@ -320,6 +368,7 @@ const VECTOR2D CalcArcCenter( const VECTOR2D& aStart, const VECTOR2D& aEnd,
const VECTOR2D CalcArcCenter( const VECTOR2D& aStart, const VECTOR2D& aMid, const VECTOR2D& aEnd )
{
VECTOR2D center;
double yDelta_21 = aMid.y - aStart.y;
double xDelta_21 = aMid.x - aStart.x;
double yDelta_32 = aEnd.y - aMid.y;
@ -368,10 +417,19 @@ const VECTOR2D CalcArcCenter( const VECTOR2D& aStart, const VECTOR2D& aMid, cons
bSlope -= std::numeric_limits<double>::epsilon();
}
}
#ifdef USE_ALTERNATE_CENTER_ALGO
// We can call ArcCenterFrom3Points from here because special cases are filtered.
CircleCenterFrom3Points( aStart, aMid, aEnd, &center );
return center;
#endif
// Prevent divide by zero error
// a small value is used. std::numeric_limits<double>::epsilon() is too small and
// generate false results
if( aSlope == 0.0 )
aSlope = std::numeric_limits<double>::epsilon();
aSlope = 1e-10;
if( bSlope == 0.0 )
bSlope = 1e-10;
// What follows is the calculation of the center using the slope of the two lines as well as
// the propagated error that occurs when rounding to the nearest nanometer. The error can be
@ -408,7 +466,6 @@ const VECTOR2D CalcArcCenter( const VECTOR2D& aStart, const VECTOR2D& aMid, cons
+ daSlopeMidEndX * daSlopeMidEndX );
double centerX = ( abSlopeStartEndY + bSlopeStartMidX - aSlopeMidEndX ) / twiceBASlopeDiff;
double dCenterX = centerX * std::sqrt( ( dCenterNumeratorX / centerNumeratorX *
dCenterNumeratorX / centerNumeratorX )
+ ( dtwiceBASlopeDiff / twiceBASlopeDiff *
@ -480,4 +537,3 @@ const VECTOR2I CalcArcCenter( const VECTOR2I& aStart, const VECTOR2I& aMid, cons
return iCenter;
}

4
pcbnew/import_gfx/graphics_importer_pcbnew.cpp
View File

@ -131,8 +131,8 @@ void GRAPHICS_IMPORTER_PCBNEW::AddArc( const VECTOR2D& aCenter, const VECTOR2D&
// The criteria used here is radius < MAX_INT / 2.
// this is not perfect, but we do not know the exact final position of the arc, so
// we cannot test the coordinate values, because the arc can be moved before being placed.
VECTOR2D center = CalcArcCenter( arc->GetStart(), arc->GetEnd(), aAngle );
double radius = ( center - arc->GetStart() ).EuclideanNorm();
VECTOR2D center = MapCoordinate( aCenter );
double radius = ( center - MapCoordinate( aStart ) ).EuclideanNorm();
double rd_max_value = std::numeric_limits<VECTOR2I::coord_type>::max() / 2.0;
if( radius >= rd_max_value )

2
pcbnew/pcb_painter.cpp
View File

@ -885,7 +885,7 @@ void PCB_PAINTER::draw( const PCB_ARC* aArc, int aLayer )
// Debug only: enable this code only to test the SHAPE_ARC::ConvertToPolyline function
// and display the polyline created by it.
#if 0
SHAPE_ARC arc( aArc->GetCenter(), aArc->GetStart(), aArc->GetAngle() / 10.0, aArc->GetWidth() );
SHAPE_ARC arc( aArc->GetCenter(), aArc->GetStart(), aArc->GetAngle(), aArc->GetWidth() );
SHAPE_LINE_CHAIN arcSpine = arc.ConvertToPolyline( m_maxError );
m_gal->SetLineWidth( m_pcbSettings.m_outlineWidth );
m_gal->SetIsFill( false );