Warp <war### [at] tagpovrayorg> wrote:
> Chambers <ben### [at] pacificwebguycom> wrote:
> > Just a quick note: a few quick calculations will show that 1600 samples
> > is not enough for things like a lightbulb across the room, or the sun in
> > the sky, to be effectively used for radiosity.
>
>   OTOH, why not make the lightbulb or the sun a light source?
>
>   I don't really understand people's obsession in making radiosity-only
> scenes. Radiosity calculates diffuse lighting only. If you use only radiosity
> to calculate the lighting of the scene, the entire scene will consist of
> purely diffusely lighted surfaces. There will be no specular component.
>
>   When a surface is purely diffuse, without any specular component to it,
> it's like a 100% matte surface, with no reflective component. There will
> be no highlights caused by light sources, which will make all surfaces
> matte and dull.
>
>   It's the specular component of lighting which makes surfaces look vivid,
> lively and brilliant, which make them have that "sparky" look. Purely matte
> surfaces are flat and dull.

Indeed.  But specular is itself a fake, a rough shortcut to the real deal:
specular is really diffuse reflection on very smooth surfaces.  Those
highlights also did not match the shape of the light sources -- at least until
you corrected that, for area lights at least -- and also why they look funky
from almost tangent angles...

I've seen people advocating the use of (glossy) reflection to more realistically
achieve that effect.

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