[Freeciv-Dev] Re: civ3 graphics system

[Jason Dorje Short <vze49r5w@xxxxxxxxxxx>]

Raimar Falke wrote:
> On Fri, Nov 22, 2002 at 01:36:27AM -0500, Jason Dorje Short wrote:
>
> > 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).
> I think this is wrong since the bounding box of the tiles are
> 128x64. This is the same size that the other tiles have. And also the
> same size that tiles have on the screen shot.
Err, what?  The graphics are the same size as an actual tile.  They're 
just centered differently.
> So we take the 4 major directions (N, S, W and E and not NE, NW, SE or
> SW) and choose the graphic. But we don't draw the graphic at the
> center of our tile but at where the grid lines meet. Very clever.
No, you're missing the beauty of it.  There _are_ only four applicable 
directions - at each intersection of tiles there are only four tiles 
meeting.  So the drawing of a single tile takes into account all 8 
adjacent tiles, since each tile is composed of 1/4 of one of these 
'corner' graphics.
> > 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.
> Looks so.
Ugh.

> > And I'm also not sure what happened to arctic - does civ3 not have
> > this terrain type?
> xtgc contains it. Look at any other modpack.
xtgc has tundra, not arctic.

> > 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.
>
> Irrigation is drawn for 3 different tech types.
Duh - I saw irrigation-PLAINS and irrigation-DESETT but missed the 
regular irrigation.  It seems clear then that there is differeent 
irrigation graphics for plains, grassland, and desert.
> > 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.
>
> z-buffer. Start drawing with the farest tile. The nearer tile will
> overdraw the farer tiles.
This is already done for iso-view.  But that wasn't my point.

This is hard to explain, for some reason.  Hmmm.

Isotrident draws a hill.  The hill has a green background - there is 
grassland around the hill.  All well and good, but it doesn't allow much 
blending.
civ3 draws a hill.  The hill does not fill the full tile; there is empty 
space around it.  Therefore the graphics engine needs to consider this 
tile grassland and draw some corner graphics underneath it.  That way 
the adjacent terrain can get properly blended with the hill.
This, I think, is what Rafal is referring to.

> > 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.
>
> How much work would it be to produce a hack to use such graphics? 
> Basic terrain drawing (no specials or cities). This would allow us to
> see if we understood this correctly. And if we can get a GPL from one
> of the artists ...
Hard to say.  I will look into it.

Note: the modpack is not a complete tileset.  There are no rivers or 
specials.  And IIRC civ3 does rivers differently anyway.
jason