[Freeciv-Dev] Re: the directional system

[Thue <thue@xxxxxxx>]

On Sunday 09 September 2001 12:33, Thue wrote:
> On Sunday 09 September 2001 10:08, Raimar Falke wrote:
> > > The DIR_DX2 system, by the way, was recently introduced to
> > > FreeCiv by (IIRC) Thue.  But, he didn't get very far in
> > > converting FreeCiv over to its use: it's only used in one place.
> >
> > Exactly. And even at this one place it provides no advantage. Thue?
> >
> >     Raimar
>
> The advantages of the DIR_D[XY] arrays is:
> -It is easy to find the opposite direction as (7-dir). This is the
> DIR_REVERSE macro.
> ­The first 3 directions are above the center, and the last 3 are
> below. So you could potentially optimize an iteration. (I don't know
> if this is used.)
>
> Most uses of iterations don't case which of the adjacent tiles it
> uses, it just needs to be fed them all one at a time, so the
> unintuitive sequence doesn't do any harm there. (The fact that
> DIR_D[XY]2 is only used one place seems to support this argument)
>
> The DIR_D[XY]2 was used that place because we actually needed to map
> array indices to their direction. Using the new "enum direction8"
> with DIR_D[XY] would be a cleaner solution here, and allow you to
> remove DIR_D[XY]2.
>
> -Thue

Umm, looking a bit closer, the roads and rails in isometric view are 
also arranged according to DIR_D[XY]2. If you want to use the current 
DIR_D[XY] there will have to be some kind of mapping. Or you could 
transform the sprites on load time to non-isometric-style setup.
(Or you could change the rest of freeciv to use DIR_DX2 as suggested, 
which may just require changing DIR_REVERSE)

-Thue