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Strip comments and inline ids onto h*

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James Gregory 2013-12-30 15:11:04 +11:00
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<meta name="vspubdate" content="07/01/97" />
<meta name="vscategory" content="Web and Software Development: Game Development,Web and Software Development: Graphics and Multimedia Development" />
<title>Michael Abrash's Graphics Programming Black Book Special Edition: Fast Convex Polygons</title><!-- HEADER -->
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<!--ISBN=1576101746//-->
<!--TITLE=Michael Abrash's Graphics Programming Black Book Special Edition//-->
<!--AUTHOR=Michael Abrash//-->
<!--PUBLISHER=The Coriolis Group, Inc.//-->
<title>Michael Abrash's Graphics Programming Black Book Special Edition: Fast Convex Polygons</title>
<meta name="chapter" content="39" />
<meta name="pages" content="733-735" />
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</tr>
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<p><b>LISTING 39.3 L39-3.ASM</b></p><!-- CODE //-->
<p><b>LISTING 39.3 L39-3.ASM</b></p>
<pre>
; Draws all pixels in the list of horizontal lines passed in, in
; mode 13h, the VGA&rsquo;s 320x200 256-color mode. Uses REP STOS to fill
@ -140,15 +133,15 @@ FillDone:
ret
_DrawHorizontalLineList endp
end
</pre><!-- END CODE //-->
</pre>
<h4 align="left"><a id="Heading7"></a>Maximizing REP STOS</h4>
<h4 align="left" id="Heading7">Maximizing REP STOS</h4>
<p>Listing 39.3 doesn&rsquo;t take the easy way out and use <b>REP STOSB</b> to fill each scan line; instead, it uses <b>REP STOSW</b> to fill as many pixel pairs as possible via word-sized accesses, using <b>STOSB</b> only to do odd bytes. Word accesses to odd addresses are always split by the processor into 2-byte accesses. Such word accesses take twice as long as word accesses to even addresses, so Listing 39.3 makes sure that all word accesses occur at even addresses, by performing a leading <b>STOSB</b> first if necessary.</p>
<p>Listing 39.3 is another case in which it&rsquo;s worth knowing the environment in which your code will run. Extra code is required to perform aligned word-at-a-time filling, resulting in extra overhead. For very small or narrow polygons, that overhead might overwhelm the advantage of drawing a word at a time, making plain old <b>REP STOSB</b> faster.</p>
<h3><a id="Heading8"></a>Faster Edge Tracing</h3>
<h3 id="Heading8">Faster Edge Tracing</h3>
<p>Finally, Listing 39.4 is an assembly language version of <b>ScanEdge</b>. Listing 39.4 is a relatively straightforward translation from C to assembly, but is nonetheless about twice as fast as Listing 39.2.</p>
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<div align="center">
Graphics Programming Black Book &copy; 2001 Michael Abrash
</div><!-- all of the reference materials (books) have the footer and subfoot reveresed -->
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