POV-Ray : Newsgroups : povray.bugreports : transmit does not work with image maps : Re: transmit does not work with image maps Server Time
23 Jun 2024 07:09:39 EDT (-0400)
  Re: transmit does not work with image maps  
From: Kenneth
Date: 22 Apr 2024 13:55:00
Message: <web.6626a436e419c9f791c33a706e066e29@news.povray.org>
Thomas de Groot <tho### [at] degrootorg> wrote:
> Op 21/04/2024 om 18:35 schreef Kenneth:
> > When using 'transmit all' with typical jpeg and png images, there is an
> > unfortunate mix of flaws in both official v3.7.0 and in the v3.8 betas--
> > different kinds of problems in each, especially with alpha-channel images.
> > See this related post from December 2022 (with some function solutions further
> > down in the post)...
> >
> > [snip]
>
> Thanks Kenneth! Somehow, I never use those cases where the bug shows, it
> appears. Good to know if I come across the problem.
>

Over the years, I have come to realize that at least part of the transmit all /
color-reversal problem in v3.7 with alpha-channel images depends on how external
apps actually construct their own alpha channels, and the steps required. My old
version of Photoshop vs. the current paint.net app (as examples) go about it in
completely different ways, at least as far as the user is concerned. And
POV-ray's transmit all results show somewhat different flaws from each, in v3.7.
Dave Blandston's image examples in his 2022 thread show the same kind of results
I used to get with Photoshop.

I have not fully tested POV-ray's own alpha-channel image output, when brought
back into POV-ray and applied to an object, then using transmit all with it. In
the 3.8 betas, my few tests look nicely correct; in 3.7, the
translucent/transparent parts of the alpha channel (gray-to-black) start showing
up as a kind of ghostly translucent white-- although this might be hard to see
when used with other layered textures.


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