[Freeciv-Dev] Re: different iso drawing algorithms

[Rafa³ Bursig <bursig@xxxxxxxxx>]

Dnia 2002.12.08 15:05 Raimar Falke napisa³(a):
> On Sun, Dec 08, 2002 at 02:06:51PM +0100, Rafa³ Bursig wrote:
> > >> SDL can pack transparent pixel in sprite but this is usefull only
> > >> for read whole pixel array.
> > >
> > >Sounds like it uses something like a run-length encoding to
> minimize
> > >memory footprint.
> > >
> > not only memory footprint but that sprites has less pexel to copy.
> > That depend on numbers of transparent pixels and aspec of sprites (
> > sprites where width >> high are faster/better compres )
> >
> > This is called RLEACCEL
>
> It is run-length encoding per line. See the top of
> <http://www.libsdl.org/cgi/cvsweb.cgi/SDL12/src/video/SDL_RLEaccel.c?rev=1.5&content-type=text/x-cvsweb-markup&sortby=date>
Yes I know.

> > >> If you want have partial acces to pixel ( first metod )you must
> > >> uncompres sprite and then read those pixels.
> > >
> > >It wouldn't matter if SDL supports a mask as a clipping
> > >object. However it looks like it only support rectangulars.
> > >
> > Yes but that isn't problem here.
> > If you want use that compresion all direct acces to pixels force
> > decompess sequence.
> > And when you want get only part of pixels ( clipping rect mask )
> from
> > sprite you must done directly acces.
> >
> > SDL can support both metod but IMO secound has better performance
> > becouse can use RLEACCEL.
>
> Can you qualify this? How much time do you need for a complete map
> canvas redraw if you use RLEACCEL and how without?
I make some test on END_GAME_STATE ( see entire map without irrigation 
, road ,units , cities and FOG !!)
I disable dithering becouse for now it work with pixel acces and we 
want see how fast is RLE
I have special function to draw entire screen map ( draw only main tile 
sprites ).
Map screen has 640x480 pixels

Normal :
Redraw time = 87, 90, 88, 93, 97, 91 ms
Flush_fullscreen time : 7 ~ 23 ms

RLE :
Redraw time = 53, 61, 56, 60, 59, 48 ms
Flush_fullscreen time : 7 ~ 19 ms

Rafal

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