andrel <a_l### [at] hotmailcom> wrote:
> Just curious, why should it not be evenly distributed

  Because the diffuse illumination of a surface depends on the angle from
which the light is coming: The more perpendicular the incoming light is to
the surface, the stronger its contribution. The strength of the contribution
decreases as a function of the cosine of the angle. If the incoming light
is parallel to the light, it has zero contribution.

  You could sample evenly along the hemisphere, but then you will be taking
tons of samples which contribute only little to the illumination. (In fact,
rather ironically, if you sample evenly, the majority of the samples will
be on the parts of the hemisphere which contribute the least to the
illumination.)

-- 
                                                          - Warp

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