From:	"Chris Wise" <Christopher DOT Wise AT eng DOT monash DOT edu DOT au>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: Allegro and blitting to screen
Date:	20 Jul 1998 03:15:53 GMT
Organization:	Materials Engineering, Monash
Lines:	43
Message-ID:	<01bdb38c$2b2b6720$cf86c282@mat-smurf.eng.monash.edu.au>
References:	<6onnuh$12p$2 AT oravannahka DOT Helsinki DOT FI>
NNTP-Posting-Host:	mat-wise.eng.monash.edu.au
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Tuomo A Turunen <tuturune AT cc DOT helsinki DOT fi> wrote in article
<6onnuh$12p$2 AT oravannahka DOT Helsinki DOT FI>...
> HELP !!??
> I'm programming a very nice game with DJGPP and allegro. I use SVGA
> 640*480*256 colors, so graphic looks good. But the problem is the
> double buffering. It's just too slow. Example :
> 
>   BITMAP *buffer = create_bitmap(640, 480);
> 
>   clear(buffer);
>   while( game_continues) {
>     // some drawwing on the buffer
>     blit(buffer, screen, 0, 0, 0, 0, 640, 480);
>   }
> 
> That is a the only way I can think of, but itsn't fast enough.
> So is there any faster way to do that 'blit(buffer, screen, ...)' ???

How fast is it? 
Make a frame rate counter that puts the frame rate on the screen.
Then experiment with the program. For example comment out the
clear(buffer);
and see what happens to the framerate.  Also try not doing any drawing to
the 
buffer and see what happens to the frame rate.  For the simple system that
I tried, the blitting was the slowest component and then clearing the
buffer.
I implemented a dirty rectangles drawing system and got a modest frame rate
increase. 

You should also try different drivers. I'm pretty sure that using vesa 2
can greatly increase your frame rate. I got around 120 fps on a pentium 166
with a rendition
verite v1000 card that has vesa 2 built in and only 35 fps on a p100 with a
cirrus logic card. Other systems were in between this.  For example 57 fps
on a p133 with an S3 trio card (no vesa 2)

If you don't have vesa 2 built into your card, try using Scitech display
doctor.

Chris Wsie

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