release winning entries of IOCCC28 under the year 2024
Congratulations to: * 2024/anders - Prize in sound coding - layered music generator * 2024/burton - Prize in pentagrammatology - wordle hard mode solver * 2024/cable1 - Prize in bot talk - LLM inference engine * 2024/cable2 - Prize in murky waters - salmon recipe * 2024/carlini - Prize in perfect timing - Intel 4004 emulation * 2024/codemeow - Prize in tray planting - bonsai generator * 2024/endoh1 - Prize in patient pointillism - slow ray tracer in CPP * 2024/endoh2 - Prize in solid body physics - rotating rigid body simulation * 2024/ferguson1 - Prize in diabolical logistics - Oregon trail pact with the devil * 2024/ferguson2 - Prize in yil-tas - Navajo code talker translator * 2024/howe - Nice accent eh-ward - mini vi * 2024/kramer - Prize in linguistic arithmetic - natural language numerical calculator * 2024/kurdyukov1 - Prize in phased periodicity - phase of the Moon * 2024/kurdyukov2 - Prize in art restoration - JPEG artifact removal * 2024/kurdyukov3 - Prize in virtual quietus - gaming VM and doom * 2024/kurdyukov4 - Prize in embiggening - encode without literals * 2024/maffiodo - Prize in creative interpretation - Jav\*script interpreter * 2024/mills - Prize in ℤ₃ - Infocom v3 story interpreter * 2024/stedolan - Best one liner - icon from MD5 * 2024/straadt - Prize in imitative rebooting - OpenRISC CPU and Linux * 2024/tmarrec - Prize in cyclonic coding - 3D tornado simulation * 2024/tompng - Prize in quasi bijection - vortex encryptor decryptor * 2024/weaver - Sur prize - rickroll Ran `make update` to perform the above. new file: 2024/burton/.entry.json
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## To build:
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``` <!---sh-->
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make all
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```
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## To use:
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``` <!---sh-->
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./prog < body.txt
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```
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## Try:
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``` <!---sh-->
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./try.sh
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```
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## Judges' remarks:
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Playing with this entry, we were able to experience joy akin to
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[what Niels Bohr and Wolfgang Pauli could have experienced when they played with the Tippe-Top](https://repository.aip.org/wolfgang-pauli-and-niels-bohr-demonstrating-tippe-top-toy).
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We invite you to experiment beyond the [try.sh](%%REPO_URL%%/2024/endoh2/try.sh), and test with these "_body.txt_" files:
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* bottle.txt
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* cylinder.txt
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* egg.txt
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* halo.txt
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* stick.txt
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* tippe-top.txt
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* tippe-top2.txt
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* tippe-top3.txt
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* top.txt
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* top2.txt
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* top3.txt
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* top4.txt
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* umbrella.txt
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* vase.txt
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For example:
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``` <!---sh-->
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./prog < vase.txt
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```
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Moreover, you should experiment with various simulation parameters. On the make line you may set:
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```
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| Perameter | Default | Meaning
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|-------------|-----------------------------------------------------|
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| WIDTH | 120 | Screen width |
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| | | |
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| HEIGHT | 24 | Screen height |
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| | | |
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| TIMESTEP | 0.01 | Simulation time step |
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| | | a smaller dt |
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| | | increases precision |
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| | | down the simulation |
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| | | |
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| RESTITUTION | 0.5 | Coefficient of restitution |
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| | | |
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| FRICTION | 0.5 | Coefficient of friction |
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| | | |
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| RPM | 750 | Initial rotation speed in RPM |
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| | | |
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| FASTRPM | 4000 | Tipple top initial rotation speed in RPM |
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| | | used by ./tipple, not ./prog |
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| | | |
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| TILT | 5 | Initial tilt angle |
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| | | in degrees |
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| | | 0 is upright |
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| | | positive values tilt to the right |
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```
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For example, to increase the "_Coefficient of friction_" to **0.75**,
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the "_Initial rotation speed in RPM_" to **600**, and the "_Initial
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tilt angle_" to **15**:
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``` <!---sh-->
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make clobber all FRICTION=0.75 RPM=600 TILT=15
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./prog < top.txt
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```
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Now we would like to see if this entry can be hacked to demonstrate the
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[Dzhanibekov effect](https://en.wikipedia.org/wiki/Tennis_racket_theorem).
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## Author's remarks:
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### A Spinning Top Simulator
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```
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@@
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@@
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@@@@@@@@@@@@
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@@ @@@@@@@@@@@@@@@@
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@@@@ @@@@@@@@@@@@@@@@
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@@@@@@@ @@@@@@@@@@@ @
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@@@@@@@@@@@ @@@
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@@@@@@@@@@@@@@@@@@@@@@@@
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@@@@@@@@@@@@@@@@@@@@@@@@
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@@@@@@@@@@@@@@@@@@@@@
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@@@@@@@@@@@@@@@@@@@@
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@@@@@@@@@@@@@@@@
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@@@@@@@@@@@@@
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@@@@@@@@@
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@@@@
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@@
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@@
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@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
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@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
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@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
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```
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This is a physics engine that simulates the motion of a rotating rigid body, such as a [top](https://en.wikipedia.org/wiki/Top).
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#### How to run
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Compilation requires specifying several `-D` options:
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```
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=1000 -Dtilt=5 -o prog prog.c
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```
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These options define the following parameters:
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* `-DW=120`: Screen width.
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* `-DH=24`: Screen height.
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* `-Ddt=0.01`: Simulation time step (a smaller `dt` increases precision but slows down the simulation).
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* `-De=0.5`: Coefficient of restitution.
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* `-Du=0.5`: Coefficient of friction.
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* `-Drpm=1000`: Initial rotation speed (in RPM).
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* `-Dtilt=5`: Initial tilt angle (in degrees; 0 is upright; positive values tilt to the right).
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Then, run the program like this:
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```
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$ ./prog < top.txt
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```
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#### Input file format
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The input file defines the shape of a rigid body. Here's an example:
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```
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// A typical spinning top
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// Use `-Drpm=1000 -Dtilt=5`
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.
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.
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. // Twirl here
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.
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.
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.
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...
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#####
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##
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# // Spin!
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##
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#####
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..
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.
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.
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. // Looks painful
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```
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This figure is rotated around its left edge to create a 3D object (a solid of revolution).
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Only solids of revolution are supported by this simulator.
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Internally, the rigid body is modeled as a collection of particles (point masses). Each character in the input file has the following meaning:
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* A full-stop (or any printable character whose LSB is 0): Represents light particle.
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* A hash (or any character whose LSB is 1): Represents heavy particle.
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* A space: Represents no particle (empty space).
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* A slash: Indicates the start of a comment; everything after it on the line is ignored.
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#### Algorithm overview
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The core algorithm works as follows:
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1. Compute the inertia tensor
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2. Compute an inverse of the tensor
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3. For each particle in contact with the floor:
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3-1. Compute the normal force
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3-2. Compute friction
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3-3. Convert these into the resultant force and torque acting on the body's center of mass
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4. Update the position, velocity, angular velocity, and orientation of the body
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For the detailed theory, refer to a physics textbook.
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To keep code size minimal, this simulator uses [quaternions](https://en.wikipedia.org/wiki/Quaternion) to represent 3D vectors and matrices.
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Quaternion multiplication is powerful, allowing the inertia tensor and its inverse to be calculated concisely, each requiring only about 100 characters of code.
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Because `math.h` doesn't natively support quaternions for these operations, it's not used at all. This also means linking with `-lm` is unnecessary.
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Motion blur is used in the rendering. You can observe it more clearly by pausing the animation (e.g., with Ctrl+S in some terminals).
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Distant points appear as colons (`:`), while closer ones appear as at-signs (`@`).
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#### Included data
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A few shape files are provided. The top*.txt files are standard spinning top shapes.
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```
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=1000 -Dtilt=5 -o prog prog.c && ./prog < top.txt
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=500 -Dtilt=5 -o prog prog.c && ./prog < top2.txt
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=500 -Dtilt=5 -o prog prog.c && ./prog < top3.txt
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=500 -Dtilt=5 -o prog prog.c && ./prog < top4.txt
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```
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The [tippe top](https://en.wikipedia.org/wiki/Tippe_top) is a top that flips itself over when spun quickly.
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```
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=2200 -Dtilt=5 -o prog prog.c && ./prog < tippe-top.txt
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=4000 -Dtilt=5 -o prog prog.c && ./prog < tippe-top2.txt
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=4000 -Dtilt=5 -o prog prog.c && ./prog < tippe-top3.txt
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```
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Spinning a boiled egg? Try this with `-Dtilt=90` to start it from a lying position.
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```
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=1300 -Dtilt=90 -o prog prog.c && ./prog < egg.txt
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```
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Spin everyday items -- no risk of breaking them:
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```
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=1000 -Dtilt=175 -o prog prog.c && ./prog < bottle.txt
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=1000 -Dtilt=5 -o prog prog.c && ./prog < bottle.txt
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=1000 -Dtilt=5 -o prog prog.c && ./prog < umbrella.txt
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=2000 -Dtilt=5 -o prog prog.c && ./prog < vase.txt
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=2000 -Dtilt=20 -o prog prog.c && ./prog < vase.txt
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```
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More shapes: `stick.txt`, `cylinder.txt`, `halo.txt`, and even `prog.c`.
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Yes, `prog.c` itself can be used as input. Try it:
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```
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$ gcc -O3 -DW=120 -DH=24 -Ddt=0.01 -De=0.5 -Du=0.5 -Drpm=1000 -Dtilt=5 -o prog prog.c && ./prog < prog.c
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```
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<!--
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Copyright © 1984-2025 by Landon Curt Noll and Leonid A. Broukhis. All Rights Reserved.
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You are free to share and adapt this file under the terms of this license:
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Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0)
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For more information, see:
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https://creativecommons.org/licenses/by-sa/4.0/
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-->
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Reference in new issue
Block a user