HW Accelerated Alpha Blending

SDL Development
#1

Hi,

I’m having problems getting a sensible framerate for my game running under Windows 2000.
When I use colour-keyed transparency, I get a frame rate of 20+fps, however when I swtich to alpha blending (which is what I would much rather use), I only get <1fps.

What’s going on?

When I check the capabilities of the graphics renderer I see that it is not hardware accellerating the alpha blended blits. I have a GeForce 2 GTS and although I’m not sure, I find it hard to believe it would accelerate this.

Is this true, does my card not accelerate alpha blending, or is it something to do with SDL?

Does anyone have any suggestion for getting a speed up?

Thanks in advance,
Andrew Wilkinson

#2

With alpha surfaces I’ve got 25fps
Do you use SDL_DisplayFormat and SDL_DisplayFormatAlpha
And software surfaces is faster than hardware surfaces for alpha

El dv, 25-01-2002 a las 12:37, ajw126 at student.cs.york.ac.uk escribi?:

Hi,

I'm having problems getting a sensible framerate for my game running under Windows 2000.
When I use colour-keyed transparency, I get a frame rate of 20+fps, however when I swtich to alpha blending (which is what I would much rather use), I only get <1fps.

What's going on?

When I check the capabilities of the graphics renderer I see that it is not hardware accellerating the alpha blended blits. I have a GeForce 2 GTS and although I'm not sure, I find it hard to believe it would accelerate this.

Is this true, does my card not accelerate alpha blending, or is it something to do with SDL?

Does anyone have any suggestion for getting a speed up?

Thanks in advance,
Andrew Wilkinson_______________________________________________
SDL mailing list
SDL at libsdl.org

http://www.libsdl.org/mailman/listinfo/sdl

#3

ajw126 at student.cs.york.ac.uk wrote:

I’m having problems getting a sensible framerate for my game running
under Windows 2000. When I use colour-keyed transparency, I get a
frame rate of 20+fps, however when I swtich to alpha blending (which
is what I would much rather use), I only get <1fps.

SDL does not accelerate alpha blits right now. Try RLE.

#4

Are there are plans for this in the future?

It would be a very useful thing to do.

Andrew> — Original Message —

From : “Mattias Engdegard”
To : sdl at libsdl.org
Date : Fri, 25 Jan 2002 14:00:12 +0100 (MET)
Subject : Re: [SDL] HW Accelerated Alpha Blending
@ajw126_at_student.cs wrote:

I’m having problems getting a sensible framerate for my game running
under Windows 2000. When I use colour-keyed transparency, I get a
frame rate of 20+fps, however when I swtich to alpha blending (which
is what I would much rather use), I only get <1fps.

SDL does not accelerate alpha blits right now. Try RLE.

#5

ajw126 at student.cs.york.ac.uk wrote:

Are there are plans for this in the future?

yes

#6

I’m having problems getting a sensible framerate for my game running under
Windows 2000.
When I use colour-keyed transparency, I get a frame rate of 20+fps,
however when I swtich to alpha blending (which is what I would much rather
use), I only get <1fps.

I use David Olofson’s glSDL which is a couple of files to add to your
project, same SDL API. and it uses openGL to accelerate your 2D. i was
running, umm 20-30fps, my app now runs at the screen refresh (85).

riki