[Freeciv-Dev] civ3 graphics system

[Jason Dorje Short <vze49r5w@xxxxxxxxxxx>]

Jason Dorje Short wrote:
> Raimar Falke wrote:
>
> > On Thu, Nov 21, 2002 at 07:19:50AM -0500, Jason Dorje Short wrote:
>
> > While I don't have any clue about how does the graphic engine of civ3
> > works the contents of this modpack
> > http://www.civfanatics.net/uploads2/cordy-terrain.zip reveals that
> > they also work with a system which is similar to our old one. Leaving
> > the extra height out of this the tiles of Mountains-snow.pcx are very
> > similar to our 16 tiles. In the x* files they blend three terrain
> > types. And yes these are a lot of tiles.
I've been looking at this civ3 modpack.  The tile system is slick, very 
slick.  But it is nothing like either our civ1 or civ2 tile systems.
Most of the terrains are not properly tile-based - they draw the 
intersections of tiles.
For instance, look at the xdgp file.  This file contains a 9x9 grid of 
graphics.  But none of these graphics corresponds a freeciv "tile" 
(which is a map square).  Rather, they contain the 3^4 = 81 different 
ways that _d_esert, _g_rassland, and _p_lains can intersect.  Thus each 
graphic contains one-quarter of the graphics for four different adjacent 
tiles.  Note that this is FAR superior to the 6^4 system I had 
suggested, since drawing a tile will take into account all 8 adjacent 
tiles (not just the 4 orthogonal ones).
xtgc = tundra + grassland + coast
xpgc = plains + grassland + coast
xggc = grassland + grassland + coast [1]
xdpc = desert + plains + coast
xdgp = desert + grassland + plains
xdgc = desert + grassland + coast


[1] Looks like there are two types of grassland.

I'm not sure what happens when four different types of terrain meet. 
Perhaps the map generator guarantees this will never happen.  And I'm 
also not sure what happened to arctic - does civ3 not have this terrain 
type?  And it appears tundra cannot border desert or plains.
The "X" here seems to indicate that these are the basic terrain types 
(desert, tundra, plains, grassland, coast), which are being blended in 
some sort of eXtreme fashion.  Or something :-).
Also note, if we add back in arctic and allow any tile to border any 
other, we're back to needing 6^4=1216 tiles (instead of just the 
6*3^4=486 that they have).  But with the "draw the intersection" system, 
they will look _much_ better.
Irrigation is drawn on a per-tile basis.  Each irrigation file contains 
a 4x4 grid of tile graphics, corresponding to the 2^4=16 possiblilities 
for adjacent irrigation.  There are two different irrigation files, for 
PLAINS and DESETT.  I'm not sure what PLAINS and DESETT are.
Mountains and hills are drawn on a per-tile basis.  'xhills' contains a 
4x4 grid containing the 2^4=16 possible hills.  'mountains' does the 
same for mountains.  However, the graphic does not fill the entire tile 
- an adjacent base terrain must be drawn "underneath" it to get the 
right blending.  I'm not sure how the adjacent terrain should be chosen. 
 I also suspect that mountains and hills are considered equivalent for 
the adjacency check.
Similarly, 'hill forests' contain 16 identical hills (identical to the 
original 16, that is), but instead of being adjacent to an X terrain 
they are adjacent to forest.  So there's forest on the slopes of the 
hill.  'hill jungle' does the same thing, for adjacent jungle.  I 
suspect that if a hill is not ENTIRELY surrounded by hill or jungle, the 
basic tile will be used.
Similarly, there is a 'mountain forests' and 'mountain jungle' files for 
mountains.
'Mountains-snow' contains the 16 mountains tiles, but they have snow on 
them.  I suspect these can also be blended naturally with the other 
mountains and with hills.
Forests and jungles I still do not understand.

jason