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

[Raimar Falke <rf13@xxxxxxxxxxxxxxxxx>]

On Wed, Apr 23, 2003 at 05:50:43PM -0500, Jason Dorje Short wrote:
> Raimar Falke wrote:
> >On Thu, Apr 17, 2003 at 08:24:58AM +0200, Raimar Falke wrote:
> >
> >
> >>If you want to speed this up you can for example write about
> >>iso-maps. Not about your implementation but about iso-maps in
> >>general. Why do we want them, what do they look like in various
> >>forms and how do they differ from the non-iso maps. This has to be
> >>written anyway and you have 2 years of knowledge about this.
> >
> >
> >I wrote what I learned about this topic down in
> ><http://www.freeciv.org/~rfalke/grid_pics2/iso_maps.html> (reading the
> >html may be easier). This is mostly for people which haven't thought
> >about this topic. I tried to avoid implementation specifics in the
> >overview section.
> 
> Pretty good.
> 
> >Open points in my eyes are:
> > - which form should be default (IMHO per performance)
> 
> For performance, non-iso maps are fastest.  But this default should be 
> determined by the default view, which is currently iso (iso-view looks a 
> lot better on an iso-map, and vice versa).

> Using "map coordinates" rather than "native coordinates" as standard is 
> fastest, since the vast, vast, vast majority of operations are done on 
> map coordinates.

I disagree here. Every tile access needs the compact form. The same is
true for normalize_map_pos and is_normal_map_pos. But without testing
we won't find out.

> > - which iso variants do we support (IMHO both)
> 
> Hmm?  The "variants" you talk about in the file are just a different 
> numbering system; there's nothing fundamentally different between them.

You can't express every instance of variant1 with an instance of
variant2. Example: try to build a variant1 map (width and height
searched) which looks the same like the variant2 map of size (9x5)
(picture in the page). IMHO this isn't possible. Because the "wdith"
of variant1 is always even.

> > - in which form is wrapping defined? Do we support multiple wrapping
> > forms (iso view form and non-iso view form)?
> 
> I don't know what this means.  Wrapping is defined for both iso and 
> non-iso maps, and is identical in both when done in "native coordinates".

Ok so the wrapping operations are defnied in the compact
form. Question: is wrapping defined in compact form the same as
wrapping defined in iso-view form? IMHO yes but I'm not sure.

> > - how can mapview code done in an easier way (IMHO with an
> > intermediate form)
> 
> Again you are lumping a whole collection of unrelated operations into 
> one term.

This is a bit terse.

I'm trying to split unnormalize_map_pos into two operations. First the
wrapping and than the rotating and scaling to pixels. What is your
opinion?

        Raimar

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