Merge branch 'master' of github.com:jarvist/FractalLight

Author: jarvist

README.md

@@ -2,14 +2,32 @@
 
 ![1D simulation](cavity_sim.png)
 
-Unbelievably the 1D version of the code compiled as is, and started running & finding eigenmodes! You must set N to be a sensible value (i.e. 1024 pixels) to compile it as the 2D version, otherwise it crashes with a cryptic linker error about truncation.
+The 2006 1D code compiled without edits, and started running & finding eigenmodes! You must set N to be a sensible value (i.e. 1024 pixels) to compile it as the 2D version, otherwise it crashes with a cryptic linker error about truncation.
 
-![Lens description](lens.png)
+### Compilation (graphical openGL version)
+
+On a 2017 Mac:
+```
+brew install fftw freeglut
+make mac
+./glFL
+```
+
+If you're on Linux, you should be able to figure it out :^)
 
-Example from 2006 of generated 2D modes:
+It should open a window and start generating eigenmodes, like this rather low-res (hey - it was 2006! I had to run this overnight on my Duron.) YouTube video. 
 
 [![2006 era modes](http://img.youtube.com/vi/-dJPs1nPTjM/0.jpg)](http://www.youtube.com/watch?v=-dJPs1nPTjM)
 
+### What is it doing?
+
+It's simulating the light bouncing around a (highly magnifying) laser cavity. It does this by solving the Huygens-Fresnel integrals in reciprocal space. Practically this means the code spends all its time flipping between real and reciprocal space via Fast Fourier Transforms. The modes form pretty self-similar patterns, when you also have a polygonal aperture in the laser caving.
+
+In the simulation, the brightness is the light intensity, and then the phase information is projected onto a colour sphere.
+
+![Lens description](lens.png)
+
+
 ## Abstract (from the 2006 MSci report)
 
 Codes were written to simulate the propagation of monochromatic light