[Freeciv-Dev] Re: different iso drawing algorithms

[Rafa³ Bursig <bursig@xxxxxxxxx>]

Dnia 2002.12.08 19:12 Raimar Falke napisa³(a):
> On Sun, Dec 08, 2002 at 06:13:41PM +0100, Rafa³ Bursig wrote:
> > >> >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
> > >
> > >Am I right that you can't use RLE if you draw the irrigation, road,
> > >units, cities and FOG because these sprites have transparent
> pixels.
> > >
> > NO... RLE is made for transparent pixels and real those pixel are
> > compressed.
> > If You have more and more transparent pixels the effect will be
> better
> > and better.
> >
> > I want have entire map that I start new game and disband all unit.
> >
> > Problem is with FOG becouse SDL havn't mask future ( has simple
> > clipping ability )
> > and when you want create fog of war effect you must use tmp surface
> > without RLE compression and that slow down drawing.
>
> Why can't you use transparency for the FOW?
I use but let me explan...

RLE is extension of transparency in SDL, you can use it or not but you 
can still have transparent pixels.
FOW...
First I do it simple. I draw tile cell ( exp. mountains ) and then draw 
on it fog cell ( tile with black rhomb and Sprite ALPHA = 96 ). This 
give nice FOW effect and was fast (RLE) but has one big bug.
When tile gfx was biger than fog rhomb some pixels ( all outside the 
rhomb ) wasn't foged.
Then I made some hack.
All tiles have 0x0(r=0,g=0,b=0) as traransparent pixels. Foged tiles 
are draw on tmp surface and this  surface is fill with r=0 g=0 b=0 
alpha = 96 color. All pixels != 0x0 are foged and pixels == 0x0 still 
are transparent ( alpha calculating with 0 still get you 0 ). Then I 
blit this tmp surface on screen.
Tmp surface can be RLE becouse we still make writes on it. This method 
give 2 more blit and is slower that first method but work in 100%
Rafal

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