[geos-devel] Problems with BufferOp when using BufferParameters

[Markus Meyer]

Mateusz,

thanks for creating the test.

Here are information about the used coordinates and the used offset 
(dumped from the code):

Coordinate #0 = 0.0, 0.0
Coordinate #1 = 100.0, 0.0
Coordinate #2 = 100.0, 100.0
Coordinate #3 = 0.0, 100.0
Coordinate #4 = 0.0, 0.0
fOffset = 5.00

Is there any chance that this problem is being fixed soon? I reviewed 
the code myself already but so far I could not easily find the problem 
so I would really need to debug into the code which might be rather 
time-consuming. So I would really appreciate if someone who is familiar 
with the inner concepts of GEOS could have a quick look at the problem, 
especially as now there is a test case for it.

Best regards,
Markus

Am 26.10.2011 20:56, schrieb Mateusz Łoskot:
> On 26 October 2011 11:14, Markus Meyer<meyer at mesw.de>  wrote:
>> I'm using GEOS 3.3.0 on Microsoft Visual Studio 2008 (Windows 7) for
>> buffering lines using BufferOp.
>>
>> I would like to use the BufferParameters class to control extended
>> parameters. However, it seems that I must be using the BufferOp class the
>> wrong way because my parameters are never accepted. To explain this, I
>> created a simple test program which offsets a rectangle.
>>
>> When I do the buffering with the static function Buffer::bufferOp() the
>> resulting geometry looks OK:
>>
>>     // Working code
>>     geos::geom::Polygon* pPolygon = dynamic_cast<geos::geom::Polygon*>(
>>         geos::operation::buffer::BufferOp::bufferOp(
>>             pLineString, fOffset, 16,
>>             geos::operation::buffer::BufferParameters::CAP_ROUND));
>>
>> When I do the buffering by using the BufferOp and BufferParameters class
>> directly, the resulted geometry looks very strange:
>>
>>     // Not working code
>>     geos::operation::buffer::BufferParameters params(
>>         16,
>>         geos::operation::buffer::BufferParameters::CAP_ROUND);
>>
>>     geos::operation::buffer::BufferOp op(pLineString, params);
>>     geos::geom::Polygon* pPolygon =
>>         dynamic_cast<geos::geom::Polygon*>(op.getResultGeometry(fOffset));
>>
>>  From my understanding, the results of both code snipets should be the same.
> Markus,
>
> As Sandro confirmed, both ways should produce the same results.
>
> I have added test case that tries to reproduce your use case.
> Here it is:
>
> http://trac.osgeo.org/geos/changeset/3509
>
> It is based on one of test geometries used across the GEOS unit tests.
> If you can provide your geometry, it would be helpful.
> Then we could replace the WKT input in the test and have it covered.
>
> Best regards,