Le 2023-12-21 à 15:42, Bald Eagle a écrit :
> Does anyone know how to implement the irid {} feature in the finish {} block of
> a texture?
> 
> Or to be more accurate, how do I get iridescence to be visible on a clear
> surface?
> 
> clipka posted some beautiful bubbles, and I can't seem to achieve anything close
> to the transparent but well-defined iridescent pattern that he gets.
> 
> I tried adding interior {ior 1.4} but that didn't work (and I get weird
> artefacts}
> 
> http://news.povray.org/povray.binaries.images/thread/%3C4ed6f24c@news.povray.org%3E/
> 
> I looked in the distro, and it appears that we're missing an example scene for
> this feature.
> 
> - BW

You just need to remember that iridescence acts pretty much the same way 
as emissive media : It adds to whatever is behind it. So, it tend to not 
show on white surfaces.

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"Bald Eagle" <cre### [at] netscapenet> wrote:
> Does anyone know how to implement the irid {} feature in the finish {} block of
> a texture?
>
> Or to be more accurate, how do I get iridescence to be visible on a clear
> surface?
>
> clipka posted some beautiful bubbles, and I can't seem to achieve anything close
> to the transparent but well-defined iridescent pattern that he gets.
>
> I tried adding interior {ior 1.4} but that didn't work (and I get weird
> artefacts}
>
> http://news.povray.org/povray.binaries.images/thread/%3C4ed6f24c@news.povray.org%3E/
>
> I looked in the distro, and it appears that we're missing an example scene for
> this feature.
>
> - BW

Hi,

there is an example in the Povray documentation:
scenes\textures\pigments\irid.pov.

I 'misused' it and added some finish_items.

Maybe it helps a bit.

Cheers Droj

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Attachments:
Download 'irid_clear.pov.txt' (4 KB)

"Bald Eagle" <cre### [at] netscapenet> wrote:
> Does anyone know how to implement the irid {} feature in the finish {} block of
> a texture?
>
> Or to be more accurate, how do I get iridescence to be visible on a clear
> surface?
>
> clipka posted some beautiful bubbles, and I can't seem to achieve anything close
> to the transparent but well-defined iridescent pattern that he gets.
>
> I tried adding interior {ior 1.4} but that didn't work (and I get weird
> artefacts}
>
> http://news.povray.org/povray.binaries.images/thread/%3C4ed6f24c@news.povray.org%3E/
>
> I looked in the distro, and it appears that we're missing an example scene for
> this feature.
>
> - BW

Here's a bubble material that I came up with back in 2012, after clipka did a
bug fix on the old irid code:

#declare M_Bubble = material {
   texture {
      pigment { rgbt 0.99 }
      finish {
         diffuse 0
         reflection { 0.05, 1 fresnel on }
         specular 0.99 roughness 0.001
         conserve_energy
         irid { 0.25
            thickness 0.25
            turbulence 1.2
         }
      }
   }
   interior { ior 1.001 }
}

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Attachments:
Download 'lucy_bubble2012.png' (2280 KB)

Preview of image 'lucy_bubble2012.png'

"Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:

> Here's a bubble material that I came up with back in 2012, after clipka did a
> bug fix on the old irid code

Yes, I remember that scene.
It's amazing how one can completely transform the feel and perceived complexity
of an object with the proper texture.
Thanks for posting that as a reminder and providing the texture.

Is that an HDRI light probe you're using?  Radiosity?

Droj just posted his version, and with just a black background, it looked ---
like poop.

But then I just pasted in the simple ground & sky code, and it magically
transformed the exact same texture into beautiful shimmering bubbles!
It truly is an amazing transformation.

I'm betting that if I take your beautiful texture and render with a poor
environment, I would make that look like oil on mud too. The environment is what
gives it life.

- BW

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"Bald Eagle" <cre### [at] netscapenet> wrote:
>
> clipka posted some beautiful bubbles, and I can't seem to achieve anything close
> to the transparent but well-defined iridescent pattern that he gets.
>
> I tried adding interior {ior 1.4} but that didn't work (and I get weird
> artefacts}

Do the artifacts look like refraction distortions?  Bubbles are not solid
spheres, but hollow thin shells, so if you put an IOR on bubbles, you would have
to model them accordingly.

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Just posting this here as a reference showing the effect of the 2 major values
for the irid {} finish.
turbulence was held at a constant 0.75, but anything between 0.25-1 works well,
and higher values might be useful for other effects.

Again, it's the environment that really lets you see the characteristic bubble
texture.

- BW

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Attachments:
Download 'iridescencetests.png' (623 KB)

Preview of image 'iridescencetests.png'

I had the idea to render a similar scene showing the effect of varying the rgb
components of the irid_wavelength global setting.

https://wiki.povray.org/content/Reference:Global_Settings#Irid_Wavelength

Even though "You may have multiple global_settings statements in a scene."

Apparently, "Whatever values were specified in the last global_settings
statement override any previous settings." and this affects all the irid{}
statements, you can't sequentially assign different global settings to objects
in the same scene.

Kinda obvious, but I did it just to check.  Bummer.

I'm voting for irid_wavelength to be moved into the irid {} code of the finish
{} block in future versions.

- BW

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"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Robert McGregor" <rob### [at] mcgregorfineartcom> wrote:
>

>
> Droj just posted his version, and with just a black background, it looked ---
> like poop.
>

> - BW

Yes BE, it looks like poop but it wasn't meant to show my artistic capabilities.
It was just a reminder for you that there is a example file for iridescence
coming with Povray.
I simply changed the pigment from white to clear using your data.

So put the blame on the author of the original file for not providing a nice
background.

- Droj

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"Droj" <803### [at] drojde> wrote:

> Yes BE, it looks like poop but it wasn't meant to show my artistic capabilities.
> It was just a reminder for you that there is a example file for iridescence
> coming with Povray.
> I simply changed the pigment from white to clear using your data.

Yes, yes, I understand completely, and I knew I was flirting with disaster
trying to explain things.


> So put the blame on the author of the original file for not providing a nice
> background.

No blame was being assigned, the point was that your texture is _beautiful_, but
if the user rendering a scene with it doesn't know the behaviour and limitations
of the irid {} feature, then a plain background will completely destroy it, and
beautiful as the texture might be - the end result is unfortunately....

:(

I beg your humble pardon for any unintended offense.

- B "the ineloquent" E

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"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Droj" <803### [at] drojde> wrote:
>
> > Yes BE, it looks like poop but it wasn't meant to show my artistic capabilities.
> > It was just a reminder for you that there is a example file for iridescence
> > coming with Povray.
> > I simply changed the pigment from white to clear using your data.
>
> Yes, yes, I understand completely, and I knew I was flirting with disaster
> trying to explain things.
>
>
> > So put the blame on the author of the original file for not providing a nice
> > background.
>
> No blame was being assigned, the point was that your texture is _beautiful_, but
> if the user rendering a scene with it doesn't know the behaviour and limitations
> of the irid {} feature, then a plain background will completely destroy it, and
> beautiful as the texture might be - the end result is unfortunately....
>
> :(
>
> I beg your humble pardon for any unintended offense.
>
> - B "the ineloquent" E

BE,
Honestly, no offense taken.
And it was not 'my texture' - the original is a Povray 3.7 scene file which I
'misused' in my strong belief to put you on the 'right track' when I saw your
first post. So no time for a neat background with tangerine trees and
marshmellow skies and a couple of fairies flying around.

And I am sure that you know what the coder gurus always used to say : RTFM! :))

Cheers
- Droj

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