Geometry Boost List: Re: [geometry] within(Poly, Poly)

Subject: Re: [geometry] within(Poly, Poly)
From: Adam Wulkiewicz (adam.wulkiewicz_at_[hidden])
Date: 2013-09-25 14:34:27

Barend Gehrels wrote:
>
> Boost.Geometry should follow the specs here. See my previous email, 
> Adam is right here.
>
> About my proposed solution, it then should obviously also take the 
> turn-info into account... The file most documenting the turns is 
> probably get_turn_info.ppt  in doc/other/test_cases (of trunk), where 
> most (or all) possible situations are clearly visualized.
>
> Besides that you might look at the traverse.cpp unit test, defining 
> TEST_WITH_SVG. It then creates an SVG showing all turns with turn-info 
> in the SVG. For example traverse_intersection_11_d.svg (but there are 
> more)
>

Thanks for this! It'd be a lot harder if I had to analyze the code and 
test how things work by myself.

> So yes now I completely understand you looking at touch (thanks for 
> the fix), which is similar but there a turn may only turn at the 
> outside, while here it may only turn at the inside. 

I'm currently analyzing the examples trying to figure out which 
combination of methods and operations will be good for within(). I hope 
it will be sufficient to analyze it locally (not taking other 
turns/points into account), like in the case of touch(). There is a lot 
of special cases, like this one:

What do think we should do with self-intersecting polygons? This is 
slightly modified traverse_intersection_52:

Is the blue polygon within the green one?

Regards,
Adam