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From: Anthony D  Baye
Subject: Stock textures and radiosity
Date: 29 Nov 2014 15:20:01
Message: <web.547a298d8b577c401538d4890@news.povray.org>
I'm working on a scene using textures from stones.inc, and I've noticed large
differences in the appearance of certain textures when rendered with radiosity.

the left side is without radiosity, the right side is with.  The primary texture
is T_Stone43 and the secondary is T_Stone39

I know that this is the result of ambient values in the textures, but the
difference seems a little severe even so.

I can't really experiment with the settings much, as my scene takes almost two
days to render with radiosity, and that's using -RVP and giving povray top
priority on processor usage.

On a side note: does anybody have a good texture tutorial?  I've created custom
textures before, but nothing terribly complex, and I'm mystified as to how some
of the definitions in the libraries work considering that they pack multiple
texture statements into one identifier. I understand that it's a layered
texture, but I'm confused as to how it gets parsed as a single texture and
subsequent definitions don't interfere.

Ideally, I'd like something that covers the new features like SSLT.

Second note: Bryce 7 has the ability to bake Light Probes for HDRI, and I was
wondering if this sort of thing could be done natively in povray using a fisheye
camera.

Regards,
A.D.B.


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From: jhu
Subject: Re: Stock textures and radiosity
Date: 29 Nov 2014 18:10:01
Message: <web.547a514c785b6936d19b0ec40@news.povray.org>
> On a side note: does anybody have a good texture tutorial?  I've created custom
> textures before, but nothing terribly complex, and I'm mystified as to how some
> of the definitions in the libraries work considering that they pack multiple
> texture statements into one identifier. I understand that it's a layered
> texture, but I'm confused as to how it gets parsed as a single texture and
> subsequent definitions don't interfere.

I've found that texture creation is going to be difficult and require lots of
experimentation no matter the renderer.


> Second note: Bryce 7 has the ability to bake Light Probes for HDRI, and I was
> wondering if this sort of thing could be done natively in povray using a fisheye
> camera.

I think so. Just output to OpenEXR or similar.


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From: Alain
Subject: Re: Stock textures and radiosity
Date: 29 Nov 2014 19:55:10
Message: <547a6aee$1@news.povray.org>

> I'm working on a scene using textures from stones.inc, and I've noticed large
> differences in the appearance of certain textures when rendered with radiosity.
>
> the left side is without radiosity, the right side is with.  The primary texture
> is T_Stone43 and the secondary is T_Stone39

On the left, the ambient part of the textures makes them visible.
On the right side, there is NO ambient, and obviously, there is no 
actual light and no object with emission in it's finish.

>
> I know that this is the result of ambient values in the textures, but the
> difference seems a little severe even so.

When rendering using radiosity, the ambient component of the textures is 
turned OFF. You need to add emission float to the finish to make the 
texture glow.

You can add a skysphere whitch, by default, is emissive.
You can add at least one actual light_source.
You can add some large object with
texture{pigment{rgb 1}finish{emission 1}}

>
> I can't really experiment with the settings much, as my scene takes almost two
> days to render with radiosity, and that's using -RVP and giving povray top
> priority on processor usage.
>
> On a side note: does anybody have a good texture tutorial?  I've created custom
> textures before, but nothing terribly complex, and I'm mystified as to how some
> of the definitions in the libraries work considering that they pack multiple
> texture statements into one identifier. I understand that it's a layered
> texture, but I'm confused as to how it gets parsed as a single texture and
> subsequent definitions don't interfere.
>
> Ideally, I'd like something that covers the new features like SSLT.
>
> Second note: Bryce 7 has the ability to bake Light Probes for HDRI, and I was
> wondering if this sort of thing could be done natively in povray using a fisheye
> camera.
>
> Regards,
> A.D.B.
>


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From: Anthony D  Baye
Subject: Re: Stock textures and radiosity
Date: 29 Nov 2014 20:35:00
Message: <web.547a7427785b69361538d4890@news.povray.org>
Alain <kua### [at] videotronca> wrote:

> > I'm working on a scene using textures from stones.inc, and I've noticed large
> > differences in the appearance of certain textures when rendered with radiosity.
> >
> > the left side is without radiosity, the right side is with.  The primary texture
> > is T_Stone43 and the secondary is T_Stone39
>
> On the left, the ambient part of the textures makes them visible.
> On the right side, there is NO ambient, and obviously, there is no
> actual light (snip)

There is light, it's just not in this area.

> You can add a skysphere whitch, by default, is emissive.
> You can add at least one actual light_source.
> You can add some large object with
> texture{pigment{rgb 1}finish{emission 1}}
>

I have six light sources.  There is no difference in lighting between the two
samples. Granted the part I'm wondering about is in moderate shadow, but it
should be receiving some of the light.  The primary texture is at least the same
color when rendered with radiosity, which indicates to me that the color of the
secondary relies too much on it's ambient value.

Regards,
A.D.B.


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From: Robert McGregor
Subject: Re: Stock textures and radiosity
Date: 30 Nov 2014 09:30:00
Message: <web.547b28eb785b693691114470@news.povray.org>
"Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:
> I have six light sources.  There is no difference in lighting between the two
> samples. Granted the part I'm wondering about is in moderate shadow, but it
> should be receiving some of the light.  The primary texture is at least the same
> color when rendered with radiosity, which indicates to me that the color of the
> secondary relies too much on it's ambient value.

Adding to the finish(es) an emission value that matches the existing ambient
value should fix that issue completely when using radiosity.

-------------------------------------------------
www.McGregorFineArt.com


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From: clipka
Subject: Re: Stock textures and radiosity
Date: 30 Nov 2014 09:32:03
Message: <547b2a63$1@news.povray.org>
Am 29.11.2014 21:18, schrieb Anthony D. Baye:
> I'm working on a scene using textures from stones.inc, and I've noticed large
> differences in the appearance of certain textures when rendered with radiosity.
>
> the left side is without radiosity, the right side is with.  The primary texture
> is T_Stone43 and the secondary is T_Stone39
>
> I know that this is the result of ambient values in the textures, but the
> difference seems a little severe even so.

This is all because the textures were designed before radiosity got 
widespread use (maybe even before the feature ever existed), and they 
were quite obviously designed for effect, rather than from physical 
principles.

Materials from stock commercial 3D models (like, say, from Renderosity, 
DAZ3D or the like) suffer from this very same problem: Someone starts 
with their favourite light setup, tweaks a figure's material until it 
looks good, and then sells it for money. But it never fits with other 
people's models, because they are tweaked to look best with some other 
light setup.


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From: Robert McGregor
Subject: Re: Stock textures and radiosity
Date: 30 Nov 2014 09:45:00
Message: <web.547b2ca2785b693691114470@news.povray.org>
"Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:
> Second note: Bryce 7 has the ability to bake Light Probes for HDRI, and I was
> wondering if this sort of thing could be done natively in povray using a fisheye
> camera.

I've created many HDR images in POV-Ray for use as image-based lighting (IBL)
and environment maps.

Use a spherical camera and render a scene at a 2:1 aspect ratio (e.g., +w2048
+h1024) and output the image as EXR using +fe

You can then wrap the image around a sphere using map_type 1 for the image_map
and a finish having some ambient and/or emissive value (e.g., ambient 1 emission
1)

-------------------------------------------------
www.McGregorFineArt.com


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From: Cousin Ricky
Subject: Re: Stock textures and radiosity
Date: 30 Nov 2014 11:05:01
Message: <web.547b3efd785b6936192ae5f10@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> Materials from stock commercial 3D models (like, say, from Renderosity,
> DAZ3D or the like) suffer from this very same problem: Someone starts
> with their favourite light setup, tweaks a figure's material until it
> looks good, and then sells it for money. But it never fits with other
> people's models, because they are tweaked to look best with some other
> light setup.

This is precisely why I included the parameters RC3M_Ambient and RC3M_Diffuse in
my Object Collection module RC3Metal.


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From: Anthony D  Baye
Subject: Re: Stock textures and radiosity
Date: 30 Nov 2014 12:45:01
Message: <web.547b567a785b69361538d4890@news.povray.org>
"Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:
> "Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:
> > I have six light sources.  There is no difference in lighting between the two
> > samples. Granted the part I'm wondering about is in moderate shadow, but it
> > should be receiving some of the light.  The primary texture is at least the same
> > color when rendered with radiosity, which indicates to me that the color of the
> > secondary relies too much on it's ambient value.
>
> Adding to the finish(es) an emission value that matches the existing ambient
> value should fix that issue completely when using radiosity.
>
> -------------------------------------------------
> www.McGregorFineArt.com

So I guess the question is: Does the emission keyword supercede ambient? should
the textures in the libraries be updated to reflect that?

and thanks for the tips on HDRI.  Now I just need a step-by-step tutorial on how
to use it in scene.

Regards,
A.D.B.


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From: Alain
Subject: Re: Stock textures and radiosity
Date: 30 Nov 2014 13:21:34
Message: <547b602e@news.povray.org>

> "Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:
>> "Anthony D. Baye" <Sha### [at] spamnomorehotmailcom> wrote:
>>> I have six light sources.  There is no difference in lighting between the two
>>> samples. Granted the part I'm wondering about is in moderate shadow, but it
>>> should be receiving some of the light.  The primary texture is at least the same
>>> color when rendered with radiosity, which indicates to me that the color of the
>>> secondary relies too much on it's ambient value.
>>
>> Adding to the finish(es) an emission value that matches the existing ambient
>> value should fix that issue completely when using radiosity.
>>
>> -------------------------------------------------
>> www.McGregorFineArt.com
>
> So I guess the question is: Does the emission keyword supercede ambient? should
> the textures in the libraries be updated to reflect that?

NO ! and NO !

>
> and thanks for the tips on HDRI.  Now I just need a step-by-step tutorial on how
> to use it in scene.
>
> Regards,
> A.D.B.
>

ambient is meant as a cheap alternative to diffuse inter-reflection that 
radiosity does.
emission is meant for textures that actualy *emit* light. Adding 
emission to most textures will wrongfully make them emit light in 
radiosity scenes.

emission never supercede ambient, they are totaly different beasts.
Most textures using high ambient are probably for simulating some amount 
of translucency. For example, PinkAlabaster is a fairly translucent 
stone and the texture for it have a high ambient. Beter done using 
subsurface that ambient, but much slower...

If you look at the metal textures, they have insane ambient that looks 
resonably good when alone with a black background. Add any environment, 
and it becomes unrealistic and often bad looking.


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