clipka <ano### [at] anonymousorg> wrote:
> Am 02.06.2010 04:08, schrieb MadKairon:
>
> > try using +fn8 +ua, first render as I posted it and then coment the second line
> > and see what happens :(
>
> I see what you mean.
>
> This is a general problem with transparency handling and emissive media
> (and also the scattering portion of scattering media):
>
> The transparency model used in the PNG file format allows only
> /blending/ of image color and whatever background the image is to be
> displayed on. That is, if you have 100% of the background colour, you
> necessarily have 0% image colour, and vice versa.
>
> Emissive media, however, just /adds/ light without taking from the
> background. That is, it would require 100% of the background colour and
> 100% image colour.
>
> Some image file formats (such as OpenEXR) theoretically don't have this
> limitation, as they are specified to use a different transparency model,
> but many applications seem to apply the wrong transparency model to
> these. As a matter of fact POV-Ray is still one of them.
>
> As it happens, the next beta will include a change to make it behave
> properly regarding output of OpenEXR, and will also get input files of
> that type (and others using that transparency model) mostly right.
> (There are still bottlenecks with input files due to conversions between
> the transparency models, which cause trouble when transparency is
> /exactly/ 100%.)
>
>
> Thus, when using PNG output file format and/or the current beta, the
> only option you have is to introduce a good deal of absorption to make
> the emissive media show at all.
>
> With future betas, you may want to try OpenEXR output instead, if that
> is an option for you. (You'll still have to add a /bit/ of absorption
> though if you should happen to plan on using it as a texture in POV-Ray.)

Ah :( thanks. Using 3.7 beta 37. Guess I need some other way of simulating
athmosphere for planets I want to use on GIMP later. Any good ideas?

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