"Cousin Ricky" <rickysttATyahooDOTcom> wrote:
> clipka <ano### [at] anonymousorg> wrote:
> > Am 02.09.2015 um 20:59 schrieb Cousin Ricky:
> > > On 2015-09-02 09:49 AM (-4), clipka wrote:
> > >> I would recommend using a non-zero fade_distance, set to be equal to the
> > >> corresponding object's radius. That more closely mimicks the
> > >> characteristics of a non-point light source.
> > >
> > > Is this true even for area_illumination with circular orient?
> >
> > Hum - that's a good question I've never thought about. But by extension
> > of what I said, if you model a single non-point light source as an array
> > of smaller light sources, then those smaller light sources'
> > fade_distance should be set equal to their radius, so for a highly
> > subdivided area_illumination light source the fade_distance should
> > indeed probably be close to zero.
>
> One complication is that points near the center of the grid are in the same
> plane as points on the edge of the grid, which should not be the case for a
> spherical extended light source.

For a common lambertian emission surface, every small area on the plane emit
light that obeys the cosine law. Obeying it give the emission along the normal
line maximum, and along the surface minimum(in fact zero).
https://en.wikipedia.org/wiki/Lambert%27s_cosine_law

It can still be simulated by an array of light_source, but each light_source
must be the case that emit light compliant the cosine law intensity.
In POV-Ray we can achieve this by using the spotlight and radius 90 falloff 90 ,
tightness 1.

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