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From: Thomas de Groot
Subject: Experimental alternative diffuse models
Date: 3 Apr 2016 04:00:12
Message: <5700cd8c@news.povray.org>
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Just a first test of the models offered by clipka in povray.beta-test:
- the plane shows pure Lambertian diffusion image_map/bump_map, with a
diffuse modulation version from Tom York;
- the cubes show the difference between pure Lambertian (left) and
oren_nayar (right) with ROUGHNESS=2;
- the spheres show the difference between pure Lambertian (left) and
lommel_seeliger (right) with K=0.8;
Except for the plane, specular 0.0 is used. No reflections.
As a first note, it seems to me that oren_nayar does not change much
with ROUGHNESS>5.
--
Thomas
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Attachments:
Download 'clipka_diffuse reflection_test.png' (1220 KB)
Preview of image 'clipka_diffuse reflection_test.png'
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On 3-4-2016 10:00, Thomas de Groot wrote:
> As a first note, it seems to me that oren_nayar does not change much
> with ROUGHNESS>5.
>
I would say: 0.0 < ROUGHNESS < ~2.0 can be considered the effective
range, optically.
--
Thomas
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From: Thomas de Groot
Subject: Re: Experimental alternative diffuse models
Date: 3 Apr 2016 08:05:52
Message: <57010720@news.povray.org>
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Alternatively, with radiosity added, and smooth spheres as more subtle
objects.
--
Thomas
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Attachments:
Download 'clipka_diffuse reflection_test.png' (1064 KB)
Preview of image 'clipka_diffuse reflection_test.png'
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From: Thomas de Groot
Subject: Re: Experimental alternative diffuse models
Date: 5 Apr 2016 03:39:14
Message: <57036ba2@news.povray.org>
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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
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Attachments:
Download 'clipka_diffuse reflection_test.png' (991 KB)
Preview of image 'clipka_diffuse reflection_test.png'
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Thomas de Groot <tho### [at] degroot org> 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.
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From: Thomas de Groot
Subject: Re: Experimental alternative diffuse models
Date: 6 Apr 2016 02:42:35
Message: <5704afdb@news.povray.org>
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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.
--
Thomas
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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.
>
> --
> Thomas
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.
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Or the carton.
Post a reply to this message
Attachments:
Download 'imag2961.jpg' (909 KB)
Preview of image 'imag2961.jpg'
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On 6-4-2016 12:28, And wrote:
> Or the carton.
>
Powdery/chalk, carton, yes that makes sense indeed for oren_nayar.
Got back to the original clipka message:
[quote] The Lommel-Seeliger model has its roots in astronomy, where it
is used to model "lunar type" (i.e. rocky or dusty) surfaces, while the
Lambertian model is used for "icy" surfaces, and weighted averages of
the two are used to model anything in between. [/quote]
What would you say for the following:
- Lambertian for icy or shiny surfaces;
- oren_nayar for fine, powdery-like surfaces;
- lommel_seeliger for coarser, dusty-like surfaces.
--
Thomas
Post a reply to this message
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Thomas de Groot <tho### [at] degrootorg> wrote:
> On 6-4-2016 12:28, And wrote:
> > Or the carton.
> >
>
> Powdery/chalk, carton, yes that makes sense indeed for oren_nayar.
>
> Got back to the original clipka message:
>
> [quote] The Lommel-Seeliger model has its roots in astronomy, where it
> is used to model "lunar type" (i.e. rocky or dusty) surfaces, while the
> Lambertian model is used for "icy" surfaces, and weighted averages of
> the two are used to model anything in between. [/quote]
>
> What would you say for the following:
>
> - Lambertian for icy or shiny surfaces;
> - oren_nayar for fine, powdery-like surfaces;
> - lommel_seeliger for coarser, dusty-like surfaces.
>
> --
> Thomas
Well. Oren-Nayar is for such objects I know. But Lambertian should be the
simplest diffuse material. I just know it is suitable for stones,
(unpainted)concrete. Lommel Seeliger I never heard.
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