[Freeciv-Dev] Re: (PR#3936) introducing native coordinates

[Jason Dorje Short <vze49r5w@xxxxxxxxxxx>]

Raimar Falke wrote:
> On Thu, Apr 10, 2003 at 11:04:02PM +0200, Raimar Falke wrote:
>
> Some more findings: 
>
> It is possible to define the rotated form on the compact form (like I
> did in the past) but it is also possible to use the view form. This
> has the advantage that you get a natural shaped neighborhood for both
> iso-view and non-iso-view. So you take the iso-view (grid_iso.png) and
> rotate it to get the rotated form (grid_iso_rot.png). This makes it
> impossible to define the neighborhood on the compact form and so
> square_map_iterate need to be changed.
You still need to define these terms if you expect anyone to understand 
this paragraph.
> There are two possible iso-view forms for a given compact map
> (9x5). See grid_iso.png and grid_iso2.png. None of these two is
> naturally to prefer. These are the neighborhood relations for these
> two possible iso-views:
>
> iso: c1, c5, b3, d3, b2, c2, b4, c4
> iso2: c2, c4, a3, e3, b2, d2, b3, d3
>
> They differ. So which one do we choose? And why? Or do we support
> both?
It looks to me like you have discovered that iso-native coordinates can 
be obtained by compressing iso-natural coordinates in either the X or 
the Y direction.  Ross chose the X direction for this, claiming that it 
leads to better cache performance with map.tiles.  I have found that 
there are some advantages to using the Y direction, but only because it 
makes some of the hacks used elsewhere in the code work out better 
(e.g., the map overview).
> Since the pictures are rather big (270k) I placed them at
> http://www.freeciv.org/~rfalke/grid_pictures/
This makes some sense.  But please try to distinguish which map you are 
representing, and which coordinate system you are using.  For instance is a
  #####
  #####
  #####

set of points, labeled as "grid_compact", supposed to be a basic set of 
coordinates for a non-iso map, or a compressed set of coordinates for an 
iso map?
jason