benn wrote:The graph is of a spectrum of wavelength versus absorption. I couldn't understand wth was going on with the various spectral quantities - but the spectral graph makes it way more obvious.

Well in that case you will need a second graph somewhere to show a graph of wavelength versus ior calculated via cauchy.
Now what would really rock is if you could interact with the graphs to visually manipulate the values with the graph updating in real time
So for for cauchy you would have a Cauchy A slider/text box (which equates to the ior parameter in indigo material spec) and a Cauchy B slider/text box and then update the graph to show the ior v wavelength curve as the parameters are changed.
For absorption your could do the same thing sort of thing but it would be best if you could drag points on the graph around (a basic spline editor would be best) and then calculate the absorption values through spline interpolation at say 10nm intervals between 350nm and 780nm.
I visually built the absorption table for my diamond material by creating a table in excel for the wavelengths mentioned above, graphed it and then manipulated the values to match the graph against a picture of a real measured graph I found online.
For a lot of info (misinfo?) on the cauchy and tabulated absorption stuff you can take a look at this thread
http://www.indigorenderer.com/forum/vie ... f=3&t=2708
...or you could just put it all in the "too hard basket"
