Hi @yistLin I came upon your repository regarding the rasiosity light modeling and I am trying to get an understanding about it. Thus, I have some questions.

1. Could please explain what is the difference between the reflectivity

   python-two-pass/utils/triangle.py

   Line 12 in b8de50c

   reflectivity: np.ndarray, shape=(3,)

   and refl

   python-two-pass/utils/triangle.py

   Line 15 in b8de50c

   refl: float

   variables. If I get it correctly the refl is the diffuse reflectance factor rho/ρ, known also as Kd. Then what is reflectivity related to?

2. With emission

   python-two-pass/utils/triangle.py

   Line 11 in b8de50c

   emission: np.ndarray, shape=(3,)

   if I am not wrong you describe the self-emittance of the patches, is that right? So for non-light source patches it should be 0.

3. Why do you describe emission, reflectivity and radiosity with 3 values?

4. If I get it correctly the spec variable is the Ks correspondence but then what refr is? Is it related with the ambient reflectance, Ka?

Thanks.