[Freeciv-Dev] Re: (PR#6721) A Quincuncial topology

["Marcelo Burda" <mburda@xxxxxxxxx>]

>rt@xxxxxxxxxxx wrote:
>> My first question is: what is a quincuncial topology?  A little research
>> turns up
>> http://www.mapleapps.com/categories/data_analysis_stats/maplemaps/html/pierce1.html
>> but I don't think that's what you're talking about (since it involves no
>> wrapping).
>
>OK, after re-reading the doc several more times I think I have it.
>
>This change is not just a matter of making a few changes to map.[ch]. 
>It will take substantial changes throughout the code.
>
>That said, I'm not opposed to this kind of change and I've had it in 
>mind all along (although IIRC Gaute had dismissed it as infeasible). 
>Some time ago we discussed having a mobius strip or a klein bottle for a 
>topology, and this requires many of the same concepts.
>
>The main concept is that _directions_ (and vectors) have to be 
>normalized, just like map positions.  For instance with an 80x40 
>quinciux (as you describe it) going north from (0,0) puts you at (0,-1) 
>which normalizes to (79,0).  But the reverse of the direction must also 
>be normalized along the way so that you normalize (0,-1,SOUTH) to 
>(79,0,NORTH).  Basically we'd need a normalize_map_dir(x,y,dir) and more 
>generally a normalize_map_vector(x,y,dx,dy).  Quite a bit of work.
>
>Other changes may be required in a few places, e.g., things that 
>currently use map_distance_vector.  Not sure about that.
>
>I'd suggest you try to get a fully working implementation patch (so 
>you'll run into all the problems along the way and we can work them 
>out).  Make sure it applies to HEAD cvs, not 1.14.  Or have you already 
>done this, and I just haven't seen it?
>
>jason
>
>
>
Yes i ave a working patch in 14.1, but there are a IA bug, then i deside to 
rewrite it in the 15 branch, i ave a working version of map_distance_vector 
too, for all "naives" toplogy and quincuncial H but i think to rewrite it from 
scratch to alow all Quincuncial one and the spin one too ( xfactor=2 , 
yfactor=0)