Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!ames!oliveb!amiga!boing!dale
From: dale@boing.UUCP (Dale Luck)
Newsgroups: comp.sys.amiga.tech
Subject: Re: Blitter problem (still there)
Message-ID: <323@boing.UUCP>
Date: 11 Jun 88 04:43:06 GMT
References: <8806090704.AA14228@jade.berkeley.edu>
Reply-To: dale@boing.UUCP (Dale Luck)
Organization: Boing, Milpitas, Ca.
Lines: 69

In article <8806090704.AA14228@jade.berkeley.edu> FATQW@USU.BITNET (Bryan Ford) writes:
>    OwnBlitter();
>
>    for(i = 0;i < Depth;i++) {
>        WaitBlit();
>        custom.bltapt = (APTR)BitMap->Planes[i];
>        custom.bltdpt = (APTR)Plane;
>        custom.bltafwm = custom.bltalwm = 0xffff;

   Not a good idea to use these kind of statements when talking to
   amiga custom chips. The writable registers are not readable and some
   compilers will generate:
     move.w	#0,custom.bltalwm
     move.w	custom.bltalwm,custom.bltafwm
   You should use seperate statements for each register load.

>        custom.bltamod = custom.bltbmod = custom.bltdmod = custom.bltcon1 = 0;

   Again not a good idea.
   See previous statement

>        if (i != 0) {
>            custom.bltbpt = (APTR)Plane;
>            custom.bltcon0 = BC0F_SRCA | BC0F_SRCB | BC0F_DEST |
>                (Color & 1 ? ABC | ABNC : NABC | NABNC);
>        } else {
>            custom.bltcon0 = BC0F_SRCA | BC0F_DEST |
>                (Color & 1 ? ABC | ABNC | ANBC | ANBNC :
>                NABC | NABNC | NANBC | NANBNC);
>        }
>        custom.bltsize = (Height << 6) | (Width >> 4);

         If your width is 1024, this will cause a 1 to be ored into
         the rows count, you should use (0x3f & (Width>>4))

>        Color >>= 1;
>    }
>
>    WaitBlit();

     This statement is not necessary as long as you do a WaitBlit before
     using the data. This will give you a little more parallelism.

>    DisownBlitter();

     Good boy

>    return(Plane);
>}

I haven't actually looked at you algorithm for lagic problems like
bad choice of minterms. I will tell you though that the flood fill
routine in the graphics library does something similar but it does it
a little more optimally. But takes more work to figure it out.
  
Basically if you have 3 or fewer bitplanes it only takes 1 blit.

If you have 4-5 bitplanes it takes 2 blits

If you have 6-7 bitplanes it takes 3 blits.
......



-- 
Dale Luck     Boing, Inc.
Although I do contract work for Amiga-LosGatos, my opinions probably
don't represent those of Commodore or its management or it's engineers,
but I think the world would be a better place if they did.