Physics simulation ray-tracing algorithm

• Clean up physics/
• Use Ray2D.calc_z to generate heatmap (avoids same-ray energy overlap and energy cell overcrowding)
• ? Update Ray2D to v3.3 with support for an array of frequencies
• ? Rename Simulation2D to Source2D => Simulation2D can be plotted and takes an env and multiple Source2D objects
• Actually a Raypack is a source

http://www.sengpielaudio.com/calculator-FactorRatioLevelDecibel.htm Sound rays…

• Ray path is frequency-independent (but rebounds aren't)

Stuff TODO: Write equation… TODO: refactor code (./src)

• Initial sweep
• Ray refining