[GRASS-dev] Re: [bug #2765] (grass) v.buffer produces strange results

[Maciej Sieczka]

Hamish wrote:

> Maciek wrote:

>> Are you absolutely sure that the output of following v.buffer
>> commands:
>>
>>  v.buffer input=ditches output=ditches_buf1 type=area buffer=1
>>  v.buffer input=ditches output=ditches_buf4 type=area buffer=4
>>
>> looks all OK after you zoom to region 'ditches_buf' included in my
>> sample dataset?
>>
>> For me it's obvious that the output is plain wrong.

> attached is a screenshot of the original vector in "aqua" on top of the
> 1 and 4 meter buffers I've just created.

Wow, this looks OK indeed. Look at my buf_bugs.png screenshot of the
same area - red is  4m buffer, green is 1m buffer. Both are all wrong.
I wonder how such a difference between your and my results is possible.

> But it doesn't matter -- I was looking for a simple example of it going
> wrong and I think I've found one:

> Can you try buffering this simple polygon and see if it works correctly
> for you? (I used a 10m buffer) If we can fix the bug causing that,
> maybe your area filling bug will go away too.

I tried. You can see the result of buffering at 10m on the attached
screendumps:

hamish_area.png 	- your input area
hamish_area_buf10.png	- 10m buffer
hamish_area_both.png	- both, overlayed

The 10m buffer is wrong. I'm curious if you obtain *the same* wrong buffer.

Maciek
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