Remove hint.html and index.html
As per discussions on GitHub the index.html and hint.html files should be deleted in favour of README.md files (from any .text/.txt/.markdown/.md files which will be turned into README.md in an upcoming commit).
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta name="GENERATOR" content="mkd2html 2.1.3 DL=DISCOUNT">
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<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=utf-8">
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<link rel="stylesheet"
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type="text/css"
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href="../hint.css">
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<title>Most shiny</title>
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</head>
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<body>
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<h1>Most shiny</h1>
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<p>Matt Zucker<br>
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<a href="mailto:mzucker1@swarthmore.edu">mzucker1@swarthmore.edu</a><br>
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<a href="http://www.swarthmore.edu/NatSci/mzucker1/">http://www.swarthmore.edu/NatSci/mzucker1/</a></p>
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<h2>Judges' comments:</h2>
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<h3>To build:</h3>
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<pre><code>make zucker
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</code></pre>
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<h3>To run:</h3>
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<pre><code>./zucker > image.ppm
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</code></pre>
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<h3>Try:</h3>
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<pre><code>./zucker "Hello!!!" > hello.ppm
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./zucker faster\! -preview > image2.ppm
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# Display the PPM image with your favorite image viewer
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</code></pre>
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<h3>Selected Judges Remarks:</h3>
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<p>The rendered image is centered and is output as a 600 by 220 pixel PPM.
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The vector font is proportional.</p>
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<p>This entry uses no local variables. None! At! All!</p>
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<h2>Author’s comments:</h2>
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<h1>An image generator</h1>
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<h2>What it does:</h2>
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<p>This program makes pretty pictures. To see the default output, try
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running</p>
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<pre><code> ./zucker > image.ppm
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</code></pre>
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<p>On the author’s 2.5 GHz MacBook Pro, this command takes approximately
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1 minute and 18 seconds to run – your runtime may vary. You will
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need an image viewer capable of displaying Netpbm images in order to
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display the output. On the Mac, <a href="http://wakaba.c3.cx/s/apps/xee">Xee</a>
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works well; otherwise <a href="http://www.imagemagick.org/">ImageMagick</a>
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and/or <a href="http://www.graphicsmagick.org/">GraphicsMagick</a> are both
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capable of displaying Netpbm files, and are available on multiple
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platforms. (Using Xee is particularly nice because it periodically
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reloads the image as it is rendered.)</p>
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<p>Aside from the default image, you may create your own by running the
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program as follows:</p>
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<pre><code> ./zucker "your text" > image.ppm
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</code></pre>
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<p>To mitigate long runtimes, the program can be invoked in a “preview”
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mode by appending <code>-preview</code> to the command line arguments, like so:</p>
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<pre><code> ./zucker faster\! -preview > image.ppm
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</code></pre>
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<p>If your platform distinguishes between binary and text streams, you
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may need to insert some code to reopen standard output in binary mode
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at the start of <code>main</code>. An ASCII platform is assumed.</p>
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<h2>Pedagogical value:</h2>
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<p>This program is quite suitable for the inexperienced programmer, due
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to a number of considerations:</p>
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<ul>
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<li><p>It is fairly short: just 4 preprocessor directives followed by 29
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lines of source.</p></li>
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<li><p>It compiles cleanly as ANSI C under gcc 4.2.1 with very strict
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compilation flags.</p></li>
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<li><p>It uses a very small subset of the keywords available in C, namely
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<code>char</code>, <code>float</code>, <code>int</code>, <code>typedef</code>, <code>struct</code>, <code>for</code>, and <code>return</code>.
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More difficult concepts such as <code>void</code>, <code>if</code>, <code>switch</code>, and
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<code>while</code> are eschewed for simplicity’s sake.</p></li>
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<li><p>It also uses a very small number of library functions: just <code>putchar</code>,
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<code>cos</code>, <code>sin</code>, <code>atan2</code>, <code>sqrt</code>, and <code>pow</code>.</p></li>
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<li><p>New programmers often prefer to use global variables when
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possible. Hence, <em>all</em> variables in this program (aside from
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function parameters) have global scope.</p></li>
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<li><p>An important aspect of the computation is graphically illustrated
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by the source code itself: the geometric construction of a
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reflection ray at an object’s surface, given the incoming
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direction and surface normal.</p></li>
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</ul>
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<h2>Further details (contains spoilers):</h2>
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<p>The program is not quite a traditional ray tracer, but a “sphere
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tracer” which uses distance fields to encode proximity to objects in
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the scene. Using sphere tracing to compute visibility instead of
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analytic ray tracing provides two advantages: first, it greatly eases
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the computation of ray-torus intersection (which would otherwise
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require solving a quartic polynomial), and second, it makes it
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possible to compute ambient occlusion (which is used to generate soft
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shadows). Unlike many traditional ray tracers and sphere tracers, this
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one uses iteration instead of recursion to compute the effect of
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reflections. This, unfortunately, resulted in the programmer going
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insane; however, program size was reduced and readability
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hindered. Neither the plaintext for the program’s default output nor
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for the Netpbm header appears in the program source, which hinders
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readability as well. Also, unlike some previous IOCCC entries which
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render ASCII text, this one uses a vector (as opposed to raster)
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font. Although the program does not generate uppercase letters, it
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handles them in a reasonable manner when they appear in the input.</p>
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<p>Even when the program is pretty-printed and preprocessor macros are
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expanded, it should be fairly resistant to analysis due to reckless
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reuse of global variables, to the inherently opaque nature of the
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math, and to its overall density. Global variables are used to store
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the results of intermediate computation. As a result, seemingly simple
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functions have important side effects. Although some of the global
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variables are simply constants, their use is overloaded. For instance,
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the variable <code>X</code> is used both as the number 40 and as the ASCII
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character <code>'('</code>. Maintainability is hindered due to hardcoding
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several aspects of the program in multiple locations. As an example,
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it is impossible to modify either the image width or height without
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changing the source in at least three different places, including
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inside the large string literal.</p>
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<p>Some of the functions are simple vector algebra operations such as
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vector construction, dot product, and normalization. However, it was
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found to be much more compact to define a single operation for
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multiply-and-add rather than to have separate functions for addition,
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subtraction, and scaling. Again, compactness led to obfuscation.</p>
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<p>This program heavily abuses <code>for</code> loops. The comma operator is used to
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get as much milage as possible out of statements inside of loop
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declarations. Between <code>for</code> loops, the comma operator, and the ternary
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operator, it was possible to avoid <code>if</code> and <code>while</code> altogether.</p>
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<p>Bitwise and arithmetic operators are used instead of logical operators
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whenever gcc doesn’t warn about it. Conversely, integer
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multiplication, division, and modulus are sometimes used in place of
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traditional bitwise operators just to keep the reader on his or her
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toes. Automatic casting between characters, integers, and floats is
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performed just about everywhere. Fascinatingly, this doesn’t seem to
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affect performance too badly. Sometimes when an explicit cast
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(i.e. from float to int) is needed, the program instead simply assigns
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to a free variable of the desired type instead. Both the <code>array[index]</code>
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and <code>index[array]</code> notations are used interchangably throughout the
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program.</p>
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<p>Two other programs were written to support development of this
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program. The first used a randomized search algorithm to deduce the
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most compact encoding of the vector font instructions into ASCII; the
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second used a modified form of the Knuth-Plass algorithm to layout the
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final text on top of a hand-generated ASCII “stencil”. The programs
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were not submitted as entries for this year’s IOCCC, not because they
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lack obfuscation, but because neither is written in C (they are in C++
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and Python, respectively).</p>
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<hr />
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<TABLE><TR>
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<TD><a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/"><img alt="Creative Commons License" style="border-width:0" src="http://i.creativecommons.org/l/by-sa/3.0/88x31.png" /></a></TD>
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<TD><P>© Copyright 1984-2012,
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<A HREF="/judges.html">Leo Broukhis, Simon Cooper, Landon Curt Noll</A>
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- All rights reserved<BR>
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This work is licensed under a <a rel="license" href="http://creativecommons.org/licenses/by-sa/3.0/">Creative Commons Attribution-ShareAlike 3.0 Unported License</a>.</P></TD>
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<TD> <!--<a href="http://validator.w3.org/check?uri=referer"><img src="http://www.w3.org/Icons/valid-html401" alt="Valid HTML 4.01 Transitional" height="31" width="88"></a>--></TD>
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</TR></TABLE>
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</body>
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</html>
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