images & source etc, posted in p.b-t.b

simple scene - 1 white plane, 1 blue 'glass' sphere with pov caustics, 1
camera and 1 point light

with Output_Alpha=On in ini file causes unslightly goof (see pictures in
p.b-t.b :) -

--
Rick

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POV-Ray News & Resources - http://Povray.co.uk
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As Rune pointed out in the binaries group, transmit+filter must be kept in
the [0..1] range when using the alpha channel.  Alpha channel support has
been greatly improved in POV 3.5, but you need to keep things within
appropriate ranges or you will get strange results.

-Nathan

"Rick [Kitty5]" <ric### [at] kitty5com> wrote in message
news:3b9d781e@news.povray.org...
> images & source etc, posted in p.b-t.b
>
> simple scene - 1 white plane, 1 blue 'glass' sphere with pov caustics, 1
> camera and 1 point light
>
> with Output_Alpha=On in ini file causes unslightly goof (see pictures in
> p.b-t.b :) -

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"Nathan Kopp" wrote:
> Alpha channel support has been greatly improved in POV 3.5,
> but you need to keep things within appropriate ranges or
> you will get strange results.

Let me tell a bit about the new design.

The alpha channel stores a transparency value for each pixel, just like
there is also stored a value for red green and blue light for each pixel. In
POV-Ray 3.5 when the alpha channel is turned on, all areas of the image
where the background is partly or fully visible will be partly or fully
transparent. Refractions of the background will also be transparent, but not
reflections.

The philosophy of the alpha channel feature in POV-Ray 3.5 is that the
background color should not be present in the color of the image when the
alpha channel is used. Instead, the amount of visible background is kept in
the alpha and *only* in the alpha channel. That ensures that images look
correct when viewed with the alpha channel.

However, it also means that images don't look right when they're viewed
without the alpha channel. POV-Ray itself doesn't support the alpha channel
in the render window, so images where the alpha channel is used may look
strange. The images need to be viewed in an image viewer that supports the
alpha channel, and in some of those programs you need to do something
special to turn on the transparency.

I suggest you have a look and see for yourself!

BTW, I was just a pre-beta tester and I do not speak for the POV-Team, just
from my own experiences.

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:    http://rsj.mobilixnet.dk (updated June 26)
POV-Ray Users:   http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk

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Rune <run### [at] mobilixnetdk> wrote:
: However, it also means that images don't look right when they're viewed
: without the alpha channel. POV-Ray itself doesn't support the alpha channel
: in the render window, so images where the alpha channel is used may look
: strange.

  Perhaps it should. I remember someone tossing the idea that when using
alpha channel, the background of the render window would have the typical
white-gray-squared pattern (used in most image processing programs) and the
pixels drawn on the window would use the alpha information to blend to this
background.
  (Of course the background pattern could be user-definable or something...)

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

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"Warp" wrote:
> Rune wrote:
> : POV-Ray itself doesn't support the alpha channel
>
>   Perhaps it should. I remember someone tossing the idea
> that when using alpha channel, the background of the render
> window would have the typical white-gray-squared pattern

Yes, that was me, and I still think it would be nice.

But it hasn't been implemented, and it's no that big a deal.

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:    http://rsj.mobilixnet.dk (updated June 26)
POV-Ray Users:   http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk

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In article <3ba0c7bc@news.povray.org> , Warp <war### [at] tagpovrayorg>  wrote:

> I remember someone tossing the idea that when using
> alpha channel, the background of the render window would have the typical
> white-gray-squared pattern (used in most image processing programs) and the
> pixels drawn on the window would use the alpha information to blend to this
> background.

You mean like the Mac version had since 3.1?

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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> You mean like the Mac version had since 3.1?

Hey, no fair! Why do the Mac guys get all the cool GUI features? >:)

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On Thu, 13 Sep 2001 11:19:02 -0500, Tony[B] wrote:
>> You mean like the Mac version had since 3.1?
>
>Hey, no fair! Why do the Mac guys get all the cool GUI features? >:)

It's obviously a sign that the POV-Team is drifting away from their
cross-platform roots in favor of a Mac-only program.

-- 
plane{-z,-3normal{crackle scale.2#local a=5;#while(a)warp{repeat x flip x}rotate
z*60#local a=a-1;#end translate-9*x}pigment{rgb 1}}light_source{-9red 1rotate 60
*z}light_source{-9rgb y rotate-z*60}light_source{9-z*18rgb z}text{ttf"arial.ttf"
"RP".01,0translate-<.6,.4,.02>pigment{bozo}}light_source{-z*3rgb-.2}//Ron Parker

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In article <3ba0db8c@news.povray.org> , "Tony[B]" <ben### [at] catholicorg> 
wrote:

>> You mean like the Mac version had since 3.1?
>
> Hey, no fair! Why do the Mac guys get all the cool GUI features? >:)

Because Mac OS provides a pixmap copy function that natively supports alpha
channels, scaling and many other neat things ... it make this feature nearly
"free" of any additional work to implement! :-)

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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In article <slr### [at] fwicom> , ron### [at] povrayorg (Ron
Parker) wrote:

> It's obviously a sign that the POV-Team is drifting away from their
> cross-platform roots in favor of a Mac-only program.

I agree, this is a bad sign! ;-)

    Thorsten

____________________________________________________
Thorsten Froehlich, Duisburg, Germany
e-mail: tho### [at] trfde

Visit POV-Ray on the web: http://mac.povray.org

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