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.)

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