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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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42-04.html
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@ -10,16 +10,9 @@
<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: Wu'ed in Haste; Fried, Stewed at Leisure</title><!-- HEADER -->
<!-- Empty Reference Subhead -->
<!--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: Wu'ed in Haste; Fried, Stewed at Leisure</title>
<meta name="chapter" content="42" />
<meta name="pages" content="784-787" />
<!--UNASSIGNED1//-->
<!--UNASSIGNED2//-->
</head>
<body>
@ -37,7 +30,7 @@
<p><br /></p>
<p><b>LISTING 42.4 L42-4.C</b></p><!-- CODE //-->
<p><b>LISTING 42.4 L42-4.C</b></p>
<pre>
/* Function to draw a non-antialiased line from (X0,Y0) to (X1,Y1), using a
* simple fixed-point error accumulation approach.
@ -105,11 +98,11 @@ void DrawLine(int X0, int Y0, int X1, int Y1, int Color)
DrawPixel(X0, Y0, Color);
} while (--DeltaX);
}
</pre><!-- END CODE //-->
</pre>
<p>Listing 42.1 isn&rsquo;t particularly fast, because it calls <b>DrawPixel()</b> for each pixel. On the other hand, <b>DrawPixel()</b> makes it easy to try out Wu antialiasing in a variety of modes; just adapt the code in Listing 42.3 for the 256-color mode you want to support. For example, Listing 42.5 shows code to draw Wu-antialiased lines in 640x480 256-color mode on SuperVGAs built around the Tseng Labs ET4000 chip with at least 512K of display memory installed. It&rsquo;s well worth checking out Wu antialiasing at 640x480. Although antialiased lines look much smoother than normal lines at 320x200 resolution, they&rsquo;re far from perfect, because the pixels are so big that the eye can&rsquo;t blend them properly. At 640x480, however, Wu-antialiased lines look fabulous; from a couple of feet away, they look as straight and smooth as if they were drawn with a ruler.</p>
<p><b>LISTING 42.5 L42-5.C</b></p><!-- CODE //-->
<p><b>LISTING 42.5 L42-5.C</b></p>
<pre>
/* Mode set and pixel-drawing functions for the 640x480 256-color mode of
* Tseng Labs ET4000-based SuperVGAs.
@ -151,7 +144,7 @@ void SetMode()
regset.x.ax = 0x002E;
int86(0x10, &amp;regset, &amp;regset);
}
</pre><!-- END CODE //-->
</pre>
<p>Listing 42.1 requires that the DAC palette be set up so that a <b>NumLevel</b>-long block of palette entries contains linearly decreasing intensities of the drawing color. The size of the block is programmable, but must be a power of two. The more intensity levels, the better. Wu says that 32 intensities are enough; on my system, eight and even four levels looked pretty good. I found that gamma correction, which gives linearly spaced intensity steps, improved antialiasing quality significantly. Fortunately, we can program the palette with gamma-corrected values, so our drawing code doesn&rsquo;t have to do any extra work.</p>
@ -174,10 +167,6 @@ void SetMode()
<div align="center">
Graphics Programming Black Book &copy; 2001 Michael Abrash
</div><!-- all of the reference materials (books) have the footer and subfoot reveresed -->
<!-- reference_subfoot = footer -->
<!-- reference_footer = subfoot -->
<!-- BEGIN SUB FOOTER -->
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</div>
</body>
</html>