# kicad-developers team mailing list archive

## Re: Question on Connectivity Algo

```So the polygon of a zone and the zone boundary points are two distinct data structures?  (And the polygon both has the fillet shapes and is inset by half the minThickness width?)

Thanks,
Jeff.

> On 7 Aug 2018, at 19:35, jp charras <jp.charras@xxxxxxxxxx> wrote:
>
> Le 07/08/2018 à 20:14, Seth Hillbrand a écrit :
>> Hi Jeff-
>>
>> Am Di., 7. Aug. 2018 um 08:07 Uhr schrieb Jeff Young <jeff@xxxxxxxxx <mailto:jeff@xxxxxxxxx>
>> <mailto:jeff@xxxxxxxxx <mailto: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
>>
>
> I agree.
> I am guessing (although I dis not write the code):
> return m_cachedPoly->ContainsPoint( p, zone->GetMinThickness() );
> should be
> return m_cachedPoly->ContainsPoint( p, zone->GetMinThickness()/2 );
>
>
> --
> Jean-Pierre CHARRAS
>
> _______________________________________________