OpticalMcInnesToPSS:

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   Convert McInnes optical coefficients to PSS format.
   PSS formulation supports ideal Lambertian coefficients only.

   Since version 7.
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   Form:
   [rhoS, rhoD, rhoA] = OpticalMcInnesToPSS( r, s )
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   ------
   Inputs
   ------
   r      (1,n)    Fraction of photons which are reflected
   s      (1,n)    Fraction of r which are reflected specularly

   -------
   Outputs
   -------
   rhoS   (1,n)    Specular reflection
   rhoD   (1,n)    Diffuse reflection
   rhoA   (1,n)    Absorption

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