Sending a beam into an equilateral triangle

Описание: In this simulation, a beam of light is sent into a cavity having a triangular shape, and exciting some resonant modes. The geometry being quite simple, one can expect a more orderly wave pattern, especially when the driving frequency is close to a resonant frequency of the triangle.
This video has two parts, showing the same simulation with two different color gradients.
Wave height: 0:00
Wave energy: 1:45
In part 1, the color hue depends on the wave height. In part 2, it depends on the wave energy, averaged over a time window. The plot shows the wave height or energy along the horizontal symmetry axis, slightly averaged over time.

Render time: 21 minutes 34 seconds
Compression: crf 25
Color scheme: Part 1 - Viridis by Nathaniel J. Smith, Stefan van der Walt and Eric Firing
https://github.com/BIDS/colormap
Part 2 - Twilight by Bastian Bechtold
https://github.com/bastibe/twilight

Music: "Knowpe" by Noir et Blanc Vie‪@NoirEtBlancVie‬

See also
https://images.math.cnrs.fr/des-ondes... for more explanations (in French) on a few previous simulations of wave equations.

The simulation solves the wave equation by discretization. The algorithm is adapted from the paper https://hplgit.github.io/fdm-book/doc...
C code: https://github.com/nilsberglund-orlea...
https://www.idpoisson.fr/berglund/sof...
Many thanks to Marco Mancini and Julian Kauth for helping me to accelerate my code!

#wave #refraction #wave_guide #polygon