POV-Ray : Newsgroups : povray.text.scene-files : negative strength blobs Server Time
20 Apr 2024 22:13:53 EDT (-0400)
  negative strength blobs (Message 1 to 7 of 7)  
From: Mike Miller
Subject: negative strength blobs
Date: 23 Feb 2023 01:25:00
Message: <web.63f706167d062486a30d213ddabc9342@news.povray.org>
POV scene file using negative strength blobs to form cavities within the blob
definition.
Mike


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Attachments:
Download 'blob_neg_pos.pov.txt' (7 KB)

From: Alain Martel
Subject: Re: negative strength blobs
Date: 23 Feb 2023 09:35:51
Message: <63f779c7$1@news.povray.org>
Le 2023-02-23 à 01:22, Mike Miller a écrit :
> POV scene file using negative strength blobs to form cavities within the blob
> definition.
> Mike

Using current POV-Ray, max_intersection is pretty much obsolete.
Then, you should use assumed_gamma 1, and set file gamma to sRGB. That 
should be the default value.
No issue with lowering the ambient_light multiplier.

New with version 3.8 :
In the camera, the right vector now defaults to the aspect ratio of the 
output image and can be omitted.

In the finish, with fresnel on, you need an interior statement setting 
the IOR to something different than 1. Otherwise, there will be NO 
reflection at all. In the present case, for M_gold_paint, using 
reflection{.2 .5 metallic} would be a better option.
Then, redefine your floor like this :
//--- floor with fresnel reflection
plane { <0,1,0> 0 material{M_floor_paint}
	interior{ior 1.5}
   }

conserve_energy only work with transparent pigments. In this scene, it 
have no effect as there are no transparent pigment.

Happy and good poving


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From: Mike Miller
Subject: Re: negative strength blobs
Date: 24 Feb 2023 15:15:00
Message: <web.63f91a171817a14aa30d213ddabc9342@news.povray.org>
Alain Martel <kua### [at] videotronca> wrote:

> > POV scene file using negative strength blobs to form cavities within the blob
> > definition.
> > Mike
>
> Using current POV-Ray, max_intersection is pretty much obsolete.
> Then, you should use assumed_gamma 1, and set file gamma to sRGB. That
> should be the default value.
> No issue with lowering the ambient_light multiplier.
>
> New with version 3.8 :
> In the camera, the right vector now defaults to the aspect ratio of the
> output image and can be omitted.
>
> In the finish, with fresnel on, you need an interior statement setting
> the IOR to something different than 1. Otherwise, there will be NO
> reflection at all. In the present case, for M_gold_paint, using
> reflection{.2 .5 metallic} would be a better option.
> Then, redefine your floor like this :
> //--- floor with fresnel reflection
> plane { <0,1,0> 0 material{M_floor_paint}
>  interior{ior 1.5}
>    }
>
> conserve_energy only work with transparent pigments. In this scene, it
> have no effect as there are no transparent pigment.
>
> Happy and good poving


Thanks. I'll clean that up. Sorry, some of this is carry over from old files and
ignorance. :)

>>  set file gamma to sRGB
is there an output flag for sRGB? thx


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From: Alain Martel
Subject: Re: negative strength blobs
Date: 24 Feb 2023 15:50:50
Message: <63f9232a$1@news.povray.org>
Le 2023-02-24 à 15:12, Mike Miller a écrit :
> Alain Martel <kua### [at] videotronca> wrote:
>> Le 2023-02-23 à 01:22, Mike Miller a écrit :
>>> POV scene file using negative strength blobs to form cavities within the blob
>>> definition.
>>> Mike
>>
>> Using current POV-Ray, max_intersection is pretty much obsolete.
>> Then, you should use assumed_gamma 1, and set file gamma to sRGB. That
>> should be the default value.
>> No issue with lowering the ambient_light multiplier.
>>
>> New with version 3.8 :
>> In the camera, the right vector now defaults to the aspect ratio of the
>> output image and can be omitted.
>>
>> In the finish, with fresnel on, you need an interior statement setting
>> the IOR to something different than 1. Otherwise, there will be NO
>> reflection at all. In the present case, for M_gold_paint, using
>> reflection{.2 .5 metallic} would be a better option.
>> Then, redefine your floor like this :
>> //--- floor with fresnel reflection
>> plane { <0,1,0> 0 material{M_floor_paint}
>>   interior{ior 1.5}
>>     }
>>
>> conserve_energy only work with transparent pigments. In this scene, it
>> have no effect as there are no transparent pigment.
>>
>> Happy and good poving
> 
> 
> Thanks. I'll clean that up. Sorry, some of this is carry over from old files and
> ignorance. :)
> 
>>>   set file gamma to sRGB
> is there an output flag for sRGB? thx
> 
> 
> 
> 
> 
Now, by default, POV-Ray output is of the .PNG format and include the 
information telling that the image should get displayed in the sRGB 
colour space. You don't need to change anything.
File gamma default to sRGB unless you change it.


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From: Mike Miller
Subject: Re: negative strength blobs
Date: 25 Feb 2023 08:00:00
Message: <web.63fa04721817a14aa30d213ddabc9342@news.povray.org>
Alain Martel <kua### [at] videotronca> wrote:
> > Alain Martel <kua### [at] videotronca> wrote:
> >>> POV scene file using negative strength blobs to form cavities within the blob
> >>> definition.
> >>> Mike
> >>
> >> Using current POV-Ray, max_intersection is pretty much obsolete.
> >> Then, you should use assumed_gamma 1, and set file gamma to sRGB. That
> >> should be the default value.
> >> No issue with lowering the ambient_light multiplier.
> >>
> >> New with version 3.8 :
> >> In the camera, the right vector now defaults to the aspect ratio of the
> >> output image and can be omitted.
> >>
> >> In the finish, with fresnel on, you need an interior statement setting
> >> the IOR to something different than 1. Otherwise, there will be NO
> >> reflection at all. In the present case, for M_gold_paint, using
> >> reflection{.2 .5 metallic} would be a better option.
> >> Then, redefine your floor like this :
> >> //--- floor with fresnel reflection
> >> plane { <0,1,0> 0 material{M_floor_paint}
> >>   interior{ior 1.5}
> >>     }
> >>
> >> conserve_energy only work with transparent pigments. In this scene, it
> >> have no effect as there are no transparent pigment.
> >>
> >> Happy and good poving
> >
> >
> > Thanks. I'll clean that up. Sorry, some of this is carry over from old files and
> > ignorance. :)
> >
> >>>   set file gamma to sRGB
> > is there an output flag for sRGB? thx
> >
> >
> >
> >
> >
> Now, by default, POV-Ray output is of the .PNG format and include the
> information telling that the image should get displayed in the sRGB
> colour space. You don't need to change anything.
> File gamma default to sRGB unless you change it.

Got it, thanks.

Also, I there a way to capture an 8 bit alpha channel in rendering?

Creating a matching scene with matt objects, no lights, rendered against a
white BG is an option. I guess you could use that method with white fog to get a
'sudo' depth of field image.

Thanks for all your help!


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From: jr
Subject: Re: negative strength blobs
Date: 25 Feb 2023 08:10:00
Message: <web.63fa079d1817a14a816b7cd96cde94f1@news.povray.org>
hi,

"Mike Miller" <mil### [at] gmailcom> wrote:
> ...
> Also, I there a way to capture an 8 bit alpha channel in rendering?

<https://wiki.povray.org/content/Reference:Image_Map#The_Filter_and_Transmit_Bitmap_Modifiers>
<https://wiki.povray.org/content/Reference:File_Output_Options>


regards, jr.


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From: Mike Miller
Subject: Re: negative strength blobs
Date: 25 Feb 2023 11:05:00
Message: <web.63fa30461817a14aa30d213ddabc9342@news.povray.org>
"jr" <cre### [at] gmailcom> wrote:
> hi,
>
> "Mike Miller" <mil### [at] gmailcom> wrote:
> > ...
> > Also, I there a way to capture an 8 bit alpha channel in rendering?
>
>
<https://wiki.povray.org/content/Reference:Image_Map#The_Filter_and_Transmit_Bitmap_Modifiers>
> <https://wiki.povray.org/content/Reference:File_Output_Options>
>
>
> regards, jr.

I skipped right over the 'background' filter when looking in the help files.
Excellent - forgot about the wiki. Great help.
....and sorry about typos. :)


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