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Geometrical Parameters

The geometry of light reflection at a surface is illustrated in Figure 2. The polar and azimuthal angles of incidence and reflection are given by (θii) and (θrr), respectively, and the solid angle of the incident light is given by i. The polar angles are measured from the surface normal. For isotropic surfaces, the BRDF is independent of φi because of rotational symmetry.

Geometry of light reflection

Figure 2: Geometry of incident and reflected light

We can express the incident energy flux dEi in terms of the incident radiance Ii, the incident angle θi and the incident solid angle i

dEi = Iicosθi • dωi (2)


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