[Freeciv-Dev] Re: Suggestion: Growning cities

[Steve Hodge <shodge@xxxxxxxxxxxxxx>]

Erik Sigra wrote:
> How were you going to make the projection of the globe to the screen? I
> suppose the best way would be to show it as earth is seen from space,
> with two ways of altering view: zoom and rotate. Although I know nothing
> about using 3D rendering libraries.

I haven't decided yet. I mainly depends on how large the sphere is (in
hexagon numbers) and how much of the globe is visible at any time. I
expect it will be unnecessary (and even undesirable) to show the whole
globe. Rather it'll be a 2D projection of a fairly small area which will
minimize the distortion. I think the best plan would probably be to try
to avoid intensive 3D stuff (such as texture mapping the terrain/units),
at least initially. The stuff I'm playing with at the moment uses Java3D
which sits on top of OpenGL or DirectX.
For manipulating the display I think zoom should be avoided if we
continue to use static images for units. If a relatively small part of
the sphere is being displayed then rotation really behaves like
translation (scrolling) anyhow.

Erik Sigra wrote:
> I found some info (pictures) about this at:
> 
>  <http://www.rickleephoto.com/mosaicfresnel.htm>
>  <http://www.met.rdg.ac.uk/~swrgrgry/buckyball/buckyball.html>

The links are good, thanks.

> (The last page claims to show a shere with 630 hexagons. I can't get
> that number with your formula. n=4 gives 470 hexagons and n=5 gives 740
> hexagons.)

Yeah it depends how you go about building the sphere. The basic idea is
you take a dodecahedron (12 pentagons for sides) or an icosahedron (20
triangles), subdivide the faces into some number of triangles and then
convert the triangles to hexagons. From a quick look it looks like in
both of those cases they started with a dodecahedron, and then divided
each pentagon into 5 triangles, further subdivided those triangles, and
final made a hexagon out of each group of six triangles. If you divide
the first set of 60 (12x5) triangles into 64 smaller triangles you get
3840 triangles which can make 630 hexagons. I'm starting with an
icosahedron and dividing each triangular face into some number of
smaller triangles and then making a single hexagon out of each one. The
formula for their method is 10 x n^2 - 10 hexagons.

Regards,
Steve Hodge