From:	qball1723 AT aol DOT com (QBall1723)
Newsgroups:	comp.os.msdos.djgpp
Subject:	can you help make THIS DJGPP inline asm work...
Date:	7 Dec 1997 18:49:33 GMT
Lines:	114
Message-ID:	<19971207184901.NAA27726@ladder02.news.aol.com>
NNTP-Posting-Host:	ladder02.news.aol.com
Organization:	AOL http://www.aol.com
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Hello,

      I posted something a couple of weeks ago about a C routine I wanted to
convert to DJGPP inline asm...

     The code was to render vertical "slivers" generated by a "wolf3D"-type ray
caster... here's as far as I've gotten:

     The sliver's are supposed to be textured from the center to the top (or
bottom respectively) of each strip...

  ...alas, all I have so far is getting the appropriate COLUMN of the texture
to be rendered... the actual ROW of the texture is in a triangular array called
scale_table, with the info for a particular sliver heights "layout" stored in
scale_row
(they're int *)....

     Yes - I'm using precomputed scales here... sort of like mapping out where
pixels will be selected from in the source bitmap, regardless of which
"texture" I might have selected to render with...

     I might be doing the following code ass-backwards, but to me... intel's
syntax still seems that way ; )

void Render_Sliver(void)
{
     __asm__ __volatile__(
        "pushl   %esi\n\t"
        "pushl   %edi\n\t"
        "pushl   %eax\n\t"
        "pushl   %ebx\n\t"
        "pushl   %ecx\n\t"
        "pushl   %edx\n\t"
        "pushw   %es\n\t"
        "pushw   %fs\n\t"

// get y * 320 + x...
     "movl $99,%ebx\n\t"
     "shll $8,%ebx\n\t"
     "movl %ebx,%eax\n\t"
     "shrl $2,%ebx\n\t"
     "addl %eax,%ebx\n\t"
     "addl _sliver_ray,%ebx\n\t"

     "movl _double_buffer,%edi\n\t"
     "addl %ebx,%edi\n\t"

     "movl _sliver_texture,%esi\n\t"

     "movl _sliver_column,%edx\n\t" // in these two lines... I really need to
extract
     "addl $2048,%edx\n\t"      // an offset from a array called scale_row...
but I
                                          // don't know how to do that... as
I'm already using
                                          // edi & esi... you may have notice I
push/pop fs
                                           // - can I use that???   

     "movl _sliver_scale,%ecx\n\t"

     // loop 1 (top of sliver)
"SliverLoop1:\n\t"
     "movb (%esi,%edx,1),%eax\n\t"
     "movb %eax,(%edi)\n\t"
     "subl $320,%edi\n\t"
     "decl %ecx\n\t"
     "jnz SliverLoop1\n\t"

// done with loop.. .I'm setting up again.

// get y * 320 + x...
     "movl $99,%ebx\n\t"
     "shll $8,%ebx\n\t"
     "movl %ebx,%eax\n\t"
     "shrl $2,%ebx\n\t"
     "addl %eax,%ebx\n\t"
     "addl _sliver_ray,%ebx\n\t"

     "movl _double_buffer,%edi\n\t"
     "movl _sliver_texture,%esi\n\t"
     "addl %ebx,%edi\n\t"

     "movl _sliver_column,%edx\n\t" 
     "addl $2048,%edx\n\t"

     "movl _sliver_scale,%ecx\n\t"

"SliverLoop2:\n\t"
     "movb (%esi,%edx,1),%eax\n\t"
     "movb %eax,(%edi)\n\t"
     "addl $320,%edi\n\t"
     "decl %ecx\n\t"
     "jnz SliverLoop2\n\t"

        "popw    %fs\n\t"
        "popw    %es\n\t"                                                      
     "popl    %edx\n\t"
        "popl    %ecx\n\t"
        "popl    %ebx\n\t"
        "popl    %eax\n\t"
        "popl    %edi\n\t"
        "popl    %esi\n\t"
        );

} // end Render_Sliver


       I'd appreciate any tips you can give me on this one...


Jim the loiterer (wannabe PC game/graphics developer)
http://members.aol.com/qball1723/index.htm
[please don't hate me because I pay too much for poor internet service!!]

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