Re: [Boost-users] [boost.geometry] buffer distance strategies

Subject: Re: [Boost-users] [boost.geometry] buffer distance strategies
From: gchlebus (gchlebus_at_[hidden])
Date: 2014-10-31 13:13:13

Hi Barend,

I really appreciate your example code, it helped me a lot. Attached you can
find my source code.
In my implementation of the anisotropic buffering I didn't know how to make
use of the distance strategy, as it was possible to make it work using only
side and join strategies.
I encountered strange behavior when changing number of points describing a
full circle. Using 360 points produced a good output, whereas 90 points
caused only the second polygon to be buffered (see attached figures). I
would be thankful if you could help me to resolve this issue as well as for
any remarks to my code.

Best,
Grzegorz

2014-10-29 23:18 GMT+01:00 Barend Gehrels [via Boost] <
ml-node+s2283326n4668567h4_at_[hidden]>:

> Hi Grzegorz,
>
>
> gchlebus wrote On 24-10-2014 16:44:
>
> > Hi,
> >
> > I am wondering whether it would be possible to achieve anisotropic
> buffering
> > (distances in neg x, pos x, neg y, pos y can have different values) of a
> > polygon using the buffer function with custom-implemented distance
> strategy.
> > What I want to achieve is presented on the figure 2-b in the following
> > paper:
> >
> http://itcnt05.itc.nl/agile_old/Conference/mallorca2002/proceedings/posters/p_molina.pdf
> >
> > I would be grateful to hear from you whether it is doable, and if
> positive,
> > how one could implement such a custom distance strategy.
> The current distance strategy has (currently) no means to get the angle,
> or a vector of the new point to be buffered. We can consider adding that.
>
> However, by writing custom strategies for join, side, point (for
> point-buffers) and possibly end (for line-buffers) you should be able to
> create this, because these have this information.
>
> Attached a program doing similar things with polygons and points (I vary
> the distance based on angle - you will have to do something with your
> anistropic model).
>
> The output is also attached.
>
> The program defines three custom strategies, all based on the same
> mechanism, to create interesting output.
> I did not do the end-strategy but that would look similar, you can look
> at the provided end-strategy (round) and apply the same function.
>
> Regards, Barend
>
>
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> *buffer_point_circle.cpp* (6K) Download Attachment
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main.cpp (9K) <http://boost.2283326.n4.nabble.com/attachment/4668617/0/main.cpp>
bufferpol_90PointsFullCircle.svg (2K) <http://boost.2283326.n4.nabble.com/attachment/4668617/1/bufferpol_90PointsFullCircle.svg>
bufferpol_360PointsFullCircle.svg (9K) <http://boost.2283326.n4.nabble.com/attachment/4668617/2/bufferpol_360PointsFullCircle.svg>

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