[SDL] Poor performance using alpha blending

Christian Topnik christian_sdl at jusos-waltrop.de
Sat Jan 25 13:06:01 PST 2003

Hi everybody,

I am using SDL for about two month now, and it didn't cause me any troubles
so far. Until now... ;)

As soon as I am using alpha blending in my game, everything gets really
slow. Of course I read through all the articles of this mailinglist.

I am using a 50% transpareny (value 128) because this should be the fastest,
and I converted the surface to the display format. I tried SDL_SetAlpha both
with and without SDL_RLEACCEL.

So I guess the point is to use software surfaces for alpha blending. But my
question is: when I use SDL_SetVideoMode with the flag SDL_SWSURFACE, does
it mean that _every_ other surface I create is a software surface? If not,
how can I tell a newly created surface, for example an image I load with
IMG_Load, to be a software surface?

It would be great if you could help me, for I don't really know what else to



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