Modeling Motion — Physics Simulations (2004)

This is original coursework from the Modeling Motion program at The Evergreen State College (2004). These are Python simulations I wrote modeling physics phenomena — springs, gravity, epidemics, numerical integration, 3D visualization — using the VPython library. I was learning physics and programming simultaneously, figuring out how to translate equations of motion into running code. Everything here is from that year of exploration.

The extensions/ directory contains a modern rewrite: the physics-modeling package with 12 interactive simulations, a CLI runner, and property-based tests. The original/ directory preserves the 2004 code exactly as written.

The Rubik's Cube

The program I'm proudest of from this course is the Rubik's cube. It wasn't a class assignment — I built it entirely from scratch as an independent project. It renders a full 3D Rubik's cube and implements face rotations with correct piece tracking.

The Rubik's cube has been extracted into its own repository: rubiks-cube

The original/rubiks-cube/ directory still contains every evolutionary stage of the original project, from early experiments (get this box to grow!.py) to the final working versions (best_cube.py, cube_class.py).

Modern Physics Simulations (extensions/)

The extensions/ directory contains the physics-modeling Python package — a full rewrite with 12 simulations available via CLI:

cd extensions && pip install -e .
physics-modeling list

Simulation	CLI Command	Description
Spring Pendulum	spring-pendulum	3D spring pendulum with interactive sliders
Double Pendulum	double-pendulum	2D double pendulum with chaotic motion and trail
Lissajous Figures	lissajous	3D Lissajous figure visualization
Bouncing/Gravity	gravity	3D bouncing objects under gravity (fountain mode)
N-Body	nbody	3D N-body gravitational simulation (binary star + particles)
Elastic Collisions	collisions	Elastic collision simulation
Hard-Sphere Gas	gas	Ideal gas hard-sphere simulation
SIR Epidemic	sir	SIR epidemic model with parameter sliders
SEIR Epidemic	seir	SEIR epidemic model with parameter sliders
Logistic Equation	logistic	Logistic growth equation visualization
Riemann Sums	riemann	Riemann sum visualization with interactive controls
Bouncing (alias)	bouncing	Alias for gravity simulation

See the extensions README for full installation and usage details.

Original Simulations (2004)

Simulation	Files	Description
Spring Pendulum	original/assignments/spring.py, springsim.py	Damped spring-mass system modeled with Euler's method
Universe Simulation	original/assignments/universe.py, fountain.py	Gravitational interactions, bouncing balls, particle fountain
Collision Detection	original/assignments/collision.py	Billiard ball elastic collisions
SIR Epidemic Model	original/assignments/sir.py	Susceptible-infected-recovered disease spread simulation
Logistic Equation	original/assignments/logistic.py	Population growth with carrying capacity
Lissajous Figures	original/assignments/lissajous.py, lissa2.py	Parametric curves rendered in 3D
Riemann Sums	original/assignments/riemann.py	Numerical integration visualization
Assembly Simulator	original/extras/assembler.py, processor.py, simulator.py	Custom instruction set simulator with its own machine language

How to Run

Modern Package (recommended)

cd extensions
pip install -e .
physics-modeling spring-pendulum

Original Code (requires VPython compatibility shim)

Set PYTHONPATH to include the compatibility shim so legacy from visual import * imports resolve correctly:

PowerShell:

$env:PYTHONPATH = ".\compat"
python original/assignments/springsim.py

Bash:

PYTHONPATH=./compat python original/assignments/springsim.py

Non-Visual Programs

Some programs don't require vpython and run directly:

python original/assignments/sir.py
python original/assignments/riemann.py
python original/assignments/logistic.py

Project Structure

modeling-motion/
├── extensions/                  # Modern physics-modeling package (12 simulations)
│   ├── physics_modeling/        # Source code (core, oscillators, gravity, etc.)
│   ├── tests/                   # Property-based and unit tests
│   ├── notebooks/               # Jupyter training notebooks
│   └── pyproject.toml           # Package configuration
├── original/                    # All original code from 2004 (preserved)
│   ├── rubiks-cube/             # Rubik's cube project (all versions)
│   ├── assignments/             # Course assignments (springs, gravity, etc.)
│   └── extras/                  # Supplementary programs (crypto, assembler, calculus)
├── compat/                      # Compatibility shim for legacy VPython imports
│   └── visual/                  # Maps `from visual import *` to modern vpython
├── rubiks-cube/                 # Standalone Rubik's cube package (separate repo)
├── docs/
│   ├── journal/                 # Weekly reflections and evaluations
│   ├── blog/                    # Technical blog posts
│   └── FUTURE_IDEAS.md          # Planned extensions and improvements
├── .github/workflows/ci.yml     # CI pipeline
└── README.md                    # This file

Known Limitations

• Programs using frame (spring.py, springsim.py) may have visual positioning issues with modern vpython. The frame object was removed from vpython — the compatibility shim provides a workaround, but composite objects may not render identically to the 2004 originals.
• Assembly simulator programs (falling.py, .mm1 files) are source code for the custom CPU instruction set, not runnable Python scripts.
• Some programs were works-in-progress. LogisticEquation.py has incomplete methods. Several cube files are intermediate experiments that may not run cleanly.
• The cube programs have many evolutionary versions. best_cube.py and cube_class.py are the most complete and functional. The others document the journey.
• Window positioning (display(x=4000, y=500)) doesn't work in modern vpython since it now runs in a browser rather than a native window.

Journal & Learning Journey

The docs/journal/ directory contains weekly reflections and evaluation worksheets from the course. These document what I was learning each week, what I struggled with, and how my understanding of physics and programming evolved together. See the journal index for a chronological listing.

Future Plans

I have ideas for extending this work — adding more simulations, numpy optimizations, interactive parameter controls, and new models. See docs/FUTURE_IDEAS.md for the full list. New code lives in the extensions/ directory, keeping the original coursework untouched.

Credits

• The Modeling Motion program at The Evergreen State College (2004)
• Barry Tolnas — instructor (credited in sir.py)
• The GlowScript examples in references/ are third-party material included for reference, not original work