[Scummvm-devel] Re: 16 bit graphics: Thoughts on how to implement it

[Marcus Comstedt]

Max Horn <fingolfin at marblehorse.org> writes:

> At 16:34 Uhr +0100 24.07.2002, Ruediger Hanke wrote:
> 
> >This is just an idea thrown in and not a really thought-over plan, but
> >I could imagine something like a 16 bit "overlay" that may be
> >drawn on top of the game screen which is used for GUI stuff. So as
> >for the game screen itself "business as usual", but add a function
> >copy_overlay_rect or so which supplies data in 16 bit. (Just a quick
> >thought)
> 
> I actually considered that approach, too. On the negative side, it
> would make live considerably harder for backends - they would have to
> support 8 bit palette data *and* 16 bit graphics data, and they would
> have to implement the overlaying etc. On the pro side, this would be
> even simpler to implement for the system independent part of ScummVM -
> basically only NewGUI would have to use the overlay stuff.
> 
> 
> Overlays should be allowed to be "transparent", though, this would
> still force some sort of conversion in the backends. Alas, they could
> just choose to not implement the alpha blending.
> 
> 
> One helpful thing (implementation wise) is that currently, if an
> overlay is showing, the 8bit part will be frozen. Backends could use
> that fact to greatly optimize things (like the above mentioned alpha
> blending).
> 
> 
> What do other porters (dreamcast, X11, Windows...) say to this?


This is fine with me.  The Dreamcast hardware eats semitransparent
overlays for breakfast.  I'd just add another textured polygon.


  // Marcus