[Freeciv-Dev] Re: different iso drawing algorithms

[Rafa³ Bursig <bursig@xxxxxxxxx>]

Dnia 2002.12.08 12:47 Rafa³ Bursig napisa³(a):
> Dnia 2002.12.08 12:26 Raimar Falke napisa³(a):
> > On Sun, Dec 08, 2002 at 05:16:01AM -0500, Jason Short wrote:
> > > When drawing tiles in isometric view, we need to follow the
> > painter's
> > > algorithm.  Since the tiles may overlap, we need to draw a tile in
> > back
> > > before we can draw a tile that may partially cover it.  But if 
> > we're
> > > only updating one tile, we can't redraw all the tiles behind it all
> > the
> > > way to the top of the screen, we just want to draw the one row of
> > tiles
> > > above the tile.
> > >
> > > There are currently used ways to limit the number of tiles drawn to
> > only
> > > those that are necessary.  I will hence name them partial tile
> > drawing
> > > and tricky buffered drawing.
> > >
> > > The attached image describes the basic concepts of the two drawing
> > > systems.
> > >
> > > So, the question becomes: which system is better?  Should we 
> > support
> > > just one of them, or try to support both?
> >
> > What can you tell us about the drawing speed? Will the partial 
> > drawing
> > be faster because it has to draw less? Or is this a non-issue?
about speed...
SDL can pack transparent pixel in sprite but this is usefull only for 
read whole pixel array.
This speed up blit about 50% becouse terrain tiles have 50% pixels 
ransparent.
If you want have partial acces to pixel ( first metod )you must 
uncompres sprite and then read those pixels.
 In SDLClient only fog tiles and edge tiles will be draw to tmp buffor 
sprite, rests are draw dirrectly to main screen buffor.
Rafal

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