[geos-devel] Fwd: Geometry/Rectangle Intersection: line touching rectangle

[Mika Heiskanen]

On 09/12/2014 01:19 PM, Sandro Santilli wrote:
> On Fri, Sep 12, 2014 at 01:08:24PM +0300, Mika Heiskanen wrote:
>> On 09/12/2014 01:03 PM, Sandro Santilli wrote:
>>> BTW, is this statement correct in the docs ?
>>>
>>>   [...] the second clips the boundaries of polygons,
>>>   not the polygons themselves.
>>>   In the latter case polygons will be converted to polylines
>>>   if any vertex is outside the clipping rectangle,
>>>    ^^^^^^^^^^^^^^^^^^^^
>>>   or will be cut out completely.
>>>
>>> Does it mean fully-contained polygons would be omitted from output ?
>>> Test 48 suggests the contrary (the polygon is found fully in output).
>>
>> No, my wording is poor. What I tried to say was that if any vertex
>> is outside, the result will always be either a polyline or nothing.
>> A polygon will result only if all vertices are in.
>
> I've changed as:
>
>   In the latter case polygons
>   will be converted to polylines only if not fully inside or fully outside
>   of the rectangle.
>
> Does it sound correct ?

Yes. Another way of saying it would be to emphasize that the resulting 
geometry consists only of edges or their parts in the original geometry,
parts of the rectangle not in the original geometry will not be used
to close polygons. as is the case in the other method call.

Regards,

Mika Heiskanen / Finnish Meteorological Institute