On 6-4-2016 13:56, clipka wrote:
> Am 06.04.2016 um 11:42 schrieb And:
>> Thomas de Groot <tho### [at] degrootorg> wrote:
>>> On 5-4-2016 15:19, And wrote:
>>>> Thomas de Groot <tho### [at] degrootorg> wrote:
>>>>> OK. One final example: a pot with albedo added as well as some specular
>>>>> value.
>>>>>
>>>>> I don't know how to interpret or make sense of all this, so some
>>>>> feedback is appreciated.
>>>>>
>>>>> --
>>>>> Thomas
>>>>
>>>> The texture is fun. It has some contrast to the before.
>>>>
>>>
>>> I confess that I am confused. The textures appear darker and somehow
>>> with less "contrast". So, my question really is: /when/ to use these
>>> alternatives instead of pure Lambertian? To me, at this stage and
>>> totally instinctively, pure Lambertian has my preference.
>
> The darker appearance is inherent in the mathematical models: At the
> same nominal brightness, the alternative models result in a lower
> effective bihemispherical albedo (ratio of total reflected light vs.
> total incoming light); a similar effect happens with the conventional
> model when you use a high "brilliance" parameter. I'll need to implement
> correction factors for that, just as I did for the "brilliance"
> mechanism, when the "albedo" keyword is used.
>
> As for having less "contrast", that is also to be expected, and is
> actually the feature making them more realistic for some materials.
>
>> Lambertian diffuse is very well truly. I think the others can be used when you
>> feel the pure diffuse is plodding, or sometimes Oren-Nayar can be used in an
>> ....powdery object like chalk.
>
> Chalk, plaster, sandstone, unglazed clay, Shapeways' 3d-printed
> "unpolished strong & flexible plastic", textiles, eggshells, even paper
> -- there's plenty of stuff in our world that is seriously non-lambertian.
>
> Granted, smooth plastic, glossy cardboard, finished wood and painted
> surfaces are quite dominant in our world, and Lambertian does quite a
> good job for those. But as soon as you have something in your scene that
> in real life exhibits non-Lambertian reflection, using one of the
> alternative models may give your scene that little extra realism.
>

Thanks. I am beginning to see/understand where this may lead my use. I 
am still a bit unsure about the dedicated use of either of the two 
alternatives though for given materials.

-- 
Thomas

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