# kicad-developers team mailing list archive

## Re: Question on Connectivity Algo

```Cool.  Thanks, Seth!

> On 7 Aug 2018, at 20:43, Seth Hillbrand <seth@xxxxxxxxxxxxx> wrote:
>
> Am Di., 7. Aug. 2018 um 12:13 Uhr schrieb Jeff Young <jeff@xxxxxxxxx <mailto:jeff@xxxxxxxxx>>:
> 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?)
>
> The polygon (m_Poly) of the zone is just the area that could be filled (in the case of copper).  The structure m_FilledPolysList is the fractured structure of polygons that acquired copper from the fill (no holes).  In the case of copper, this is the same as m_RawPolysList
>
> In the case of non-copper, m_Poly is the same as before, the points given by the user for the outside limits.  Now, however, m_RawPolysList is the resulting smoothed zone (if chamfer or fillet is enabled) with additional polygons in the set for holes and m_FilledPolysList is the fractured (no holes), inset polygon structure.
>
> -Seth
>
>
>
>
> Thanks,
> Jeff.
>
>
>> On 7 Aug 2018, at 19:35, jp charras <jp.charras@xxxxxxxxxx <mailto: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
>>
>> _______________________________________________