# kicad-developers team mailing list archive

## Re: Question on Connectivity Algo

Hi Jeff-

Am Di., 7. Aug. 2018 um 08:07 Uhr schrieb Jeff Young <jeff@xxxxxxxxx>:

> When building zone connectivity, we go through the following two routines:
>
> bool ContainsPoint( const VECTOR2I p ) const
> {
>     auto zone = static_cast<ZONE_CONTAINER*> ( Parent() );
>     return m_cachedPoly->ContainsPoint( p, zone->GetMinThickness() );
> }
>
> int ContainsPoint( const VECTOR2I& aP, int aClearance = 0 )    // const
> {
>     if( containsPoint(aP) )
>         return 1;
>
>     if( aClearance > 0 )
>         return checkClearance ( aP, aClearance );
>
>     return 0;
> }
>
>
> Why is zone->GetMinThickness() used?  Isn’t that the minimum web thickness
> of the zone?
>

Minimum thickness sets the trace thickness for the zone.  The outside
points of the filled zone sets the maximum size, so the actual zone outline
is offset into the zone area by half the min thickness.  This means that
the corners are rounded (see attached image) and need to be considered when
determining interior points.

> And in the second routine, why check both?  Isn’t checkClearance() a
> superset of containsPoint()?
>

The clearance sets the minimum distance outside of the outer boundary.  So,
in the case of a zone, clearance is half the trace width.  This is outside
of the polygon, so it needs a distinct check.

Looking at this, it seems we _might_ have a discrepancy between
m_ZoneMinThickness representing half or all of the zone trace width.

-Seth

Attachment: min_width.png
Description: PNG image