On 2016-07-27 05:29 AM (-4), scott wrote:
>>   #declare Acc = <0, 0, 0>;
>>   #for (I, 0, 35)
>>     #local Wl = 380 + I * 10;
>>     #declare Acc = Acc + CMF_xyz (Wl) * LEVEL; // Illuminant E
>>   #end
>>   #declare C = Acc / 36;
>
> What units are the return value from CMF_xyz (specifically, is it nm^-1
> or does it return the xyz for a 10nm band width)? I suspect you need to
> multiply the value by 10 if you are using 10 nm width spectral bands.
>
> Also I don't see why you need the Acc/36 line, the result should be the
> sum of all the wavelength contributions, not the average.
>
> If you change those two things, does the below give the correct result?
>
> #declare Acc = <0, 0, 0>;
> #for (I, 0, 35)
>   #local Wl = 380 + I * 10;
>   #declare Acc = Acc + CMF_xyz (Wl) * 10 * LEVEL; // Illuminant E
>   #end
> #declare C = Acc;

It's even worse:

xyz <53.4116, 53.4265, 53.3845>
rgb <64.3517, 50.6749, 48.5072>

This suggests I should divide by 10 instead of multiplying by 10, but I 
don't know why that should be.

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