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Lecture 14: Material Modeling (16)

how are index of refractions calculated?

jacklishufan

Since the index of refractions is dependent on the wavelength on input rays, the light of different colors may refract to directions (one example is the rainbow in the previous slide). However, since we do not actually keep track of the distribution of wavelength in RTX, how could we simulate the "rainbow" effect in the previous slide? I image it requires doing some integral over wavelength and refraction index as a function of wavelength.

jacklishufan

Also, in physicals we know materials such as uniaxial crystal have different IOR in different directions, however the material abstraction in CG seems independent of actual geometry. Are there any efforts to keep track this? I think these could be an issue if we are rendering things like jewelry

longh2000

Interesting to see how material types tell about refraction angles, so that we can render, and also in real life inverse process can be used to identify material from observed angles.

william-fei

I notice here that air is not a vacuum but rather has value 1.0029. Does this mean that when we view the world, our eyesight is constantly getting "pushed" slightly? So if I'm looking up, my view iteratively pushes itself further upward?

bbcd0921

So in this case, n_i is incident index and n_t is refracted index?

sZwX74

@bbcd0921 yes @william-fei I think so? However, the difference is so minuscule that I don't think it particularly matters. In fact, based on a google search, long-range sniping accounts for the rotation and curvature of the earth but doesn't account for the index of refraction of air, so I think that is telling of how much of a factor it really is