POV-Ray : Newsgroups : povray.macintosh : Alpha channel Server Time: 26 Feb 2021 20:51:51 GMT
  Alpha channel (Message 1 to 5 of 5)  
From: kurtz le pirate
Subject: Alpha channel
Date: 27 Jan 2021 18:46:11
Message: <6011b4f3$1@news.povray.org>
Hi,


I try to have "transparent" background for one image. In accordance with 
the documentation, i check the "Add Alpha Channel" in output options. 
The file type is png. I had already used this option with the previous 
versions without any problem. It even seems to me that in the image 
window, a button could raise the transparency (the grey/white checkerboard).

This feature seems no longer exist.
Error on my part or forgotten option ?


My config :
Povray 3.8.0-alpha.10013324.unofficial
Mac OS X 10.10.5 (14F2511) - Yosemite.


Note : work with MacMegaPov v1.2.1 r3 (Universal)
Display windows is empty, but pgn file is OK.



Regards
-- 
Kurtz le pirate
Compagnie de la Banquise


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From: Le Forgeron
Subject: Re: Alpha channel
Date: 29 Jan 2021 17:28:03
Message: <601445a3$1@news.povray.org>
Le 27/01/2021 à 19:46, kurtz le pirate a écrit :
> Hi,
> 
> 
> I try to have "transparent" background for one image. In accordance with
> the documentation, i check the "Add Alpha Channel" in output options.
> The file type is png. I had already used this option with the previous
> versions without any problem. It even seems to me that in the image
> window, a button could raise the transparency (the grey/white
> checkerboard).
> 
> This feature seems no longer exist.
> Error on my part or forgotten option ?

The preview display does not have the checkerboard anymore, and does not
display the alpha channel. But the generated png file should be ok.

From my (old) memory, for png with alpha, +UA on the command line AND
something about "background" in the scene (NO background at all).

Also, that's where sky_sphere might be a problem : it's a background too.

Ok, you will get alpha with background/sky_sphere as long as you have
some transmit or filter part in the colour of background/sky_sphere.
And +UA.


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From: Yvo Smellenbergh
Subject: Re: Alpha channel
Date: 30 Jan 2021 08:58:49
Message: <60151fc9@news.povray.org>
On 2021-01-27 18:46:11 +0000, kurtz le pirate said:

> Hi,
> 
> 
> I try to have "transparent" background for one image. In accordance 
> with the documentation, i check the "Add Alpha Channel" in output 
> options. The file type is png. I had already used this option with the 
> previous versions without any problem. It even seems to me that in the 
> image window, a button could raise the transparency (the grey/white 
> checkerboard).
> 
> This feature seems no longer exist.
> Error on my part or forgotten option ?
> 
> 
> My config :
> Povray 3.8.0-alpha.10013324.unofficial
> Mac OS X 10.10.5 (14F2511) - Yosemite.
> 
> 
> Note : work with MacMegaPov v1.2.1 r3 (Universal)
> Display windows is empty, but pgn file is OK.
> 
> 
> 
> Regards

It is still there:
Turn on "Add Alpha Channel" in the "image & Quality" panel on the 
preferences panel.

And use this simple example scene:

camera {
	perspective
	location < 0.0, 0.0, -5>
	right x * 1
	up y * 3/4
	angle 60
	look_at < 0.0, 0.0, 0.0>
}
light_source {
	< 0.0, 100, 100>
	rgb <1.000000, 1.000000, 1.000000> * 1.0
}

sky_sphere {
	pigment {
		rgbt <0.016749, 0.198007, 0.999977, 1.000000>
	}
}
sphere {
	<0.0, 0.0, 0.0>, 0.5
				pigment {
				rgb <0.500000, 1.0, 1.0>
			}
	
}

--
Yvo

-- 
-------------------------------------------------------------------------------------------


POV-Ray 3.7 unofficial: http://megapov.inetart.net/povrayunofficial_mac/
UberPOV Mac: http://megapov.inetart.net/uberpov_mac/index.html#Mac
MegaPOV: http://megapov.inetart.net
E-mail: yvo(DOT)s(AT)gmx.net


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From: kurtz le pirate
Subject: Re: Alpha channel
Date: 30 Jan 2021 16:19:37
Message: <60158719$1@news.povray.org>
On 30/01/2021 09:58, E-mailyvo s gmx.net wrote:

> 
> It is still there:
> Turn on "Add Alpha Channel" in the "image & Quality" panel on the 
> preferences panel.
> 
> And use this simple example scene:
> 
> camera {
>      perspective
>      location < 0.0, 0.0, -5>
>      right x * 1
>      up y * 3/4
>      angle 60
>      look_at < 0.0, 0.0, 0.0>
> }
> light_source {
>      < 0.0, 100, 100>
>      rgb <1.000000, 1.000000, 1.000000> * 1.0
> }
> 
> sky_sphere {
>      pigment {
>          rgbt <0.016749, 0.198007, 0.999977, 1.000000>
>      }
> }
> sphere {
>      <0.0, 0.0, 0.0>, 0.5
>                  pigment {
>                  rgb <0.500000, 1.0, 1.0>
>              }
> 
> }

Looking at your example, I found the guilty !
The sky_sphere pigment has transmit attribute...

background { color <0,0,0> }
	=> no alpha channel

background { color <0,0,0> transmit 1 }
	=> alpha channel OK !

*transmit* is a key
I don't remember needing to add this in the old versions.




-- 
Kurtz le pirate
Compagnie de la Banquise


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From: Bald Eagle
Subject: Re: Alpha channel
Date: 30 Jan 2021 17:35:01
Message: <web.6015985f8ebab0251f9dae300@news.povray.org>
kurtz le pirate <kur### [at] gmailcom> wrote:

> Looking at your example, I found the guilty !
> The sky_sphere pigment has transmit attribute...
>
> background { color <0,0,0> }
>  => no alpha channel
>
> background { color <0,0,0> transmit 1 }
>  => alpha channel OK !
>
> *transmit* is a key
> I don't remember needing to add this in the old versions.

Right - but if you created an object with transmit 1, then you wouldn't even see
it at all.  So your background with "transmit 1" is invisible - so why even have
it?
Just delete / comment out those lines.

If background and sky_sphere can be overwritten with new values, it might be
useful to pop a little macro into a newbie include file that will be the last
line in the .pov file.  Then background and sky_sphere can be overwritten with
clear textures a s a quick diagnostic / fix, and as a reminder to those who
haven't used it in a long time...

include "newuser.inc"
transparent_background ()


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