Parallel and perpendicular polarization terms.Īt this point, it is necessary to draw a distinction among several important With this simplifyingĪssumption, the Fresnel reflectance is the average of the squares of the It is randomly oriented with respect to the light wave. Pbrt we will make the common assumption that light is unpolarized that is, Reflectance for two different polarization states of the incident illumination.īecause the visual effect of polarization is limited in most environments, in The surface normal, the Fresnel equations specify the material’s corresponding Given the index of refraction and the angle which the incident ray makes with The Fresnel equations describe theĪmount of light reflected from a surface they are the solution to These terms are directionally dependent and cannot be captured by constant For physically accurate reflection or refraction, Necessary to compute the fraction of incoming light that is reflected or In addition to the reflected and transmitted directions, it is also We will use the Greek letter eta, pronounced “eta,” to denote the index of refraction. Travels in a particular medium than in a vacuum. The index of refraction describes how much more slowly light The incident ray is in and the index of refraction for the medium it isĮntering. Snell’s law is based on the index of refraction for the medium that (One of the exercises at the end of thisĬhapter is to derive Snell’s law using Fermat’s principle from optics.) Surface normal bold n Subscript to the angle theta Subscript normal i between the incident ray and the Relates the angle theta Subscript normal t between the transmitted direction and the įor transmission, we again have phi Subscript normal o Baseline equals phi Subscript normal i Baseline plus pi ,Īnd the outgoing direction theta Subscript t is given by Snell’s law, which Theta Subscript normal i Baseline equals theta Subscript normal o Baseline commaĪnd where phi Subscript normal o Baseline equals phi Subscript normal i Baseline plus pi.
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