Add alt code, PDF + format/typo checks 2011/zucker
The alt code is based on the author's remarks - it sets binary mode on stdout. The PDF is about sphere tracing. Added it in case the link ever dies. Format/typo check README.md file. Updated .gitignore.
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Cody Boone Ferguson committed
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@@ -1,6 +1,7 @@
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image.ppm
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hello.ppm
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image2.ppm
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ioccc2011.ppm
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zucker
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zucker.orig
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prog.orig
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@@ -114,8 +114,8 @@ OBJ= ${PROG}.o
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DATA=
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TARGET= ${PROG}
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#
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ALT_OBJ=
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ALT_TARGET=
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ALT_OBJ= ${PROG}.alt.o
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ALT_TARGET= ${PROG}.alt
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#################
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@@ -138,6 +138,9 @@ ${PROG}: ${PROG}.c
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alt: data ${ALT_TARGET}
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@${TRUE}
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${PROG}.alt: ${PROG}.alt.c
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${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
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# data files
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#
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data: ${DATA}
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+118
-76
@@ -4,6 +4,9 @@
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make
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```
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There is an alternate version which should work for Windows which distinguishes
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binary mode from text mode. See [alternate code](#alternate-code) below.
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## To use:
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@@ -21,14 +24,29 @@ make
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Display the PPM image with your favorite image viewer.
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The author gave options for macOS but we note that you can just do:
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## Alternate code:
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This version uses the Windows functions `_setmode()` and `_fileno()` to set
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binary mode on `stdout` which the author noted would be necessary for systems
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that distinguish binary and text.
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### Alternate build:
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```sh
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open image.ppm
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make alt
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```
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which will open `Preview.app` which will let you look at the image no problem.
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No need to install additional software.
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### Alternate use:
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Use `zucker.alt` as you would `zucker` above.
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### Alternate try:
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Try `zucker.alt` instead of `zucker` above.
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## Judges' remarks:
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@@ -49,18 +67,40 @@ This program makes pretty pictures. To see the default output, try
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running
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```sh
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./zucker > image.ppm
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./zucker > ioccc2011.ppm
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```
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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, [Xee](http://wakaba.c3.cx/s/apps/xee)
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works well; otherwise [ImageMagick](http://www.imagemagick.org/)
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and/or [GraphicsMagick](http://www.graphicsmagick.org/) 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.)
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On the author's 2.5 GHz MacBook Pro, this command takes approximately 1 minute
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and 18 seconds to run -- your runtime may vary. You will need an image viewer
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capable of displaying [Netpbm images](https://en.wikipedia.org/wiki/Netpbm) in
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order to display the output. On the Mac, the system supplied `Preview.app` works
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well; otherwise [ImageMagick](http://www.imagemagick.org/) and/or
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[GraphicsMagick](http://www.graphicsmagick.org/) are both capable of displaying
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Netpbm files, and are available on multiple platforms.
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With macOS you can type at the command line:
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```sh
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open ioccc2021.ppm
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```
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and it will open image in the default application Preview.app.
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To use ImageMagick you might do something like:
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```sh
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convert ioccc2011.ppm ioccc2011.png
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```
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and then open `ioccc2011.png` in your viewer of choice.
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To use GraphicsMagick you might do something like:
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```sh
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gm convert ioccc2011.ppm ioccc2011.png
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```
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and then open `ioccc2011.png` in your viewer of choice.
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Aside from the default image, you may create your own by running the
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program as follows:
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@@ -76,71 +116,75 @@ mode by appending `-preview` to the command line arguments, like so:
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./zucker faster\! -preview > image.ppm
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```
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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 `main`. An ASCII platform is assumed.
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If your platform distinguishes between binary and text streams, you may need to
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insert some code to reopen standard output in binary mode at the start of
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`main()` (the provided [alternate version](#alternate-code) will set binary mode
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on `stdout` in Windows). An ASCII platform is assumed.
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#### Pedagogical value:
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This program is quite suitable for the inexperienced programmer, due
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to a number of considerations:
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* It is fairly short: just 4 preprocessor directives followed by 29
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lines of source.
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* It is fairly short: just 4 preprocessor directives followed by 29
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lines of source.
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* It compiles cleanly as ANSI C under gcc 4.2.1 with very strict
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compilation flags.
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* It compiles cleanly as ANSI C under gcc 4.2.1 with very strict
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compilation flags.
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* It uses a very small subset of the keywords available in C, namely
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`char`, `float`, `int`, `typedef`, `struct`, `for`, and `return`.
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More difficult concepts such as `void`, `if`, `switch`, and
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`while` are eschewed for simplicity's sake.
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* It uses a very small subset of the keywords available in C, namely
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`char`, `float`, `int`, `typedef`, `struct`, `for`, and `return`.
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More difficult concepts such as `void`, `if`, `switch`, and
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`while` are eschewed for simplicity's sake.
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* It also uses a very small number of library functions: just `putchar`,
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`cos`, `sin`, `atan2`, `sqrt`, and `pow`.
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* It also uses a very small number of library functions: just `putchar(3)`,
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`cos(3)`, `sin(3)`, `atan2(3)`, `sqrt(3)`, and `pow(3)`.
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* New programmers often prefer to use global variables when
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possible. Hence, *all* variables in this program (aside from
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function parameters) have global scope.
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* 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.
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* New programmers often prefer to use global variables when
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possible. Hence, *all* variables in this program (aside from
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function parameters) have global scope.
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* 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.
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\
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#### Further details (contains spoilers):
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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.
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The program is not quite a traditional [ray
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tracer](https://en.wikipedia.org/wiki/Ray_tracing_(graphics)), but a "[sphere
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tracer](sphere-tracing.pdf)" which uses distance fields to encode proximity to
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objects in the scene. Using sphere tracing to compute visibility instead of
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analytic ray tracing provides two advantages: first, it greatly eases the
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computation of [ray-torus](https://en.wikipedia.org/wiki/Toric_lens#Torus)
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intersection (which would otherwise require solving a quartic polynomial), and
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second, it makes it possible to compute [ambient
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occlusion](https://en.wikipedia.org/wiki/Ambient_occlusion) (which is used to
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generate soft shadows). Unlike many traditional ray tracers and sphere tracers,
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this one uses iteration instead of recursion to compute the effect of
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reflections. This, unfortunately, resulted in the programmer going insane;
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however, program size was reduced and readability hindered. Neither the
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plaintext for the program's default output nor for the Netpbm header appears in
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the program source, which hinders readability as well. Also, unlike some
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previous IOCCC entries which render ASCII text, this one uses a vector (as
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opposed to raster) font. Although the program does not generate uppercase
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letters, it handles them in a reasonable manner when they appear in the input.
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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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translated, it should be fairly resistant to analysis due to reckless
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reuse of global variables, the inherently opaque nature of the
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math, and 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 `X` is used both as the number 40 and as the ASCII
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the variable `X` is used both as the number `40` and as the ASCII
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character `'('`. 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.
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inside the large string literal `J`.
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Some of the functions are simple vector algebraic operations such as
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vector construction, dot product, and normalization. However, it was
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@@ -153,26 +197,24 @@ get as much mileage as possible out of statements inside of loop
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declarations. Between `for` loops, the comma operator, and the ternary
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operator, it was possible to avoid `if` and `while` altogether.
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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 `array[index]`
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and `index[array]` notations are used interchangeably throughout the
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program.
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Bitwise and arithmetic operators are used instead of logical operators whenever
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gcc doesn't warn about it. Conversely, integer multiplication, division, and
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modulus are sometimes used in place of traditional bitwise operators just to
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keep the reader on his or her toes. Automatic casting between characters,
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integers, and floats is performed just about everywhere. Fascinatingly, this
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doesn't seem to 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 to a
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free variable of the desired type instead. Both the `array[index]` and
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`index[array]` notations are used interchangeably throughout the program.
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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).
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Two other programs were written to support development of this program. The
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first used a randomized search algorithm to deduce the most compact encoding of
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the vector font instructions into ASCII; the second used a modified form of the
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[Knuth-Plass](https://en.wikipedia.org/wiki/Line_wrap_and_word_wrap) algorithm
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to layout the final text on top of a hand-generated ASCII "stencil". The
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programs 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++ and
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Python, respectively).
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## Copyright and CC BY-SA 4.0 License:
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@@ -0,0 +1,35 @@
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#include <stdio.h>
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#include <math.h>
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#include <fcntl.h>
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#include <io.h>
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#define E return
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#define S for
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char*J="LJFFF%7544x^H^XXHZZXHZ]]2#( #@@DA#(.@@%(0CAaIqDCI$IDEH%P@T@qL%PEaIpBJCA\
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I%KBPBEP%CBPEaIqBAI%CAaIqBqDAI%U@PE%AAaIqBcDAI%ACaIaCqDCI%(aHCcIpBBH%E@aIqBAI%A\
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AaIqB%AAaIqBEH%AAPBaIqB%PCDHxL%H@hIcBBI%E@qJBH#C@@D%aIBI@D%E@QB2P#E@'C@qJBHqJBH\
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%C@qJBH%AAaIqBAI%C@cJ%" "cJ" "CH%C@qJ%aIqB1I%PCDI`I%BAaICH%KH+@'JH+@KP*@%S@\
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3P%H@ABhIaBBI%P@S@PC#", *j ,*e;typedef float x;x U(x a){E a<0?0:a>1?1:a; }
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typedef struct{x c,a,t; } y;y W={1,1,1},Z={0,0,0},B[99],P,C,M,N,K,p,s,d,h
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;y G(x t,x a,x c){K.c=t ; K.t=c; K.a=a;E K;}int T=-1,b=0,r,F=-111,(*m)(i\
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nt)=putchar,X=40,z=5,o, a, c,t=0 ,n,R;y A(y a,y b,x c){E G(a.c+b.c*c,a.a
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+c*b.a,b.t*c+a.t);}x H= .5,Y =.66 ,I,l=0,q,w,u,i,g;x O(y a,y b){E q=a.t*
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b.t+b.c*a.c+a.a*b.a;}x Q(){E A(P,M,T ),O(K,K)<I?C=M,I=q:0;}y V(y a){E A(Z,
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a,pow(O(a,a),-H));}x D(y p){S(I=X,P =p,b=T; M=B[++b],p=B[M.c+=8.8-l*.45,
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++b],b<=r;Q())M=p.t?q =M_PI*H,w=atan2( P.a-M.a,P.c-M.c) /q,o=p.c-2,a=p.a+1,t=
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o+a,w=q*(w>t+H*a?o: w>t?t:w<o-H*a?t :w<o?o:w),A( M,G(cos(w),sin(w),0),
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1):A(M,p,U(O(A(P,M,T) ,p)/O(p,p))); M=P;M.a=- .9;o=P.c/8+8;o^=a=P.t
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/8+8; M=Q ()?o&1 ?G(Y,0,0):W :G(Y,Y,1);E sqrt (I)-.45;}
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int main(int L,char**k){_setmode(_fileno(stdin),_O_BINARY);S(e=L>1?1[z=0,k]:J ;*e &&l<24 ;
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++e)S(o=a =0,j =J+9;(c= *++j)&& !(o&&c< X&&(q=l+=w) );o ?o=*j++/
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32,b++[B] =G(q +=*j/8&3,* j&7,0 ),B[r =b++]=G((c/8& 3)*( o<2?
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T:1), (c& 7)+ 1e-4,o>2),1: (o =(a =(c-=X)<0?w=c+6 ,t= a+1:c?(t
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?0:m(c),a ):*++j)==((*e|32 ) ^z)&&1[j]-X));S(z =3*( L<3);++
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F<110;)S(L=-301;p=Z,++L<300;m( p.c),m(p.a),m(p.t))S(c=T;++c<=z;)S(h
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=G(-4,4.6,29),d=V(A(A(A(Z,V(G(5,0 ,2)),L+L+c/2),V(G(2,-73,0)),F+F+c%2),G
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(30.75,-6,-75),20)),g=R=255-(n=z)*64; R*n+R;g*=H){S(u=i=R=0;!R&&94>(u+=i=D(h=
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A(h,d,i)));R=i<.01);S(N=V(A(P,C, T)),q=d.t*d.t,s=M,u=1;++i<6*R;u-=
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U(i/3-D(A(h,N,i/3)))/pow( 2,i));s=R?i=pow(U(O(N,V(A(
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M=V(G(T,1,2)),d,T)))) ,X),p=A(p,W,g*i),u*=U(
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O(N,M))*H*Y+Y,g*= n--?Y-Y*i:1-i,s:G(
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q,q,1); p=A(p,s ,g*u);h=A(h,N,.1
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);d=A(d,N,-2*O (d,N));}E 0;}
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@@ -3268,6 +3268,17 @@ the author's comments (along with looking up the function for the right header
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file). To build try the alt rule of the Makefile.
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## [2011/zucker](2011/zucker/zucker.c) ([README.md](2011/zucker/README.md]))
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Cody added [alt code](2011/zucker/README.md#alternate-code) that should work on
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Windows, based on the author's remarks that if the system distinguishes binary
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and text then `stdout` needs to be set to binary mode.
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Cody also added the PDF file
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[sphere-tracing.pdf](2011/zucker/sphere-tracing.pdf) in case the link eventually
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dies.
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# <a name="2012"></a>2012
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Reference in new issue
Block a user