Posted by Georg Mischler on July 18, 2001 at 10:35:46:In Reply to: alpha channel transparency in Radiance posted by Kevin Matthews on July 17, 2001 at 23:54:55:
>>Is it Radiance itself that can't handle alpha transparency? Or is it just
>>RenderCity's implementation?>To the best of my knowledge, it's a built-in limitation of the current
>versions of Radiance. We'd love to be able to support alpha textures in
>Radiance without having to write the software for it. The problem isn't
>fundamental -- Radiance certainly could be upgraded to support alpha channel
>transparency. But it's not trivial -- it would take a noticeable chunk of
>software engineering.Procedural transparency control as such has always been possible
with Radiance, just that there was no simple way to control that
transparency based on image data. But at least starting with
3R1p20, Radiance supports the "mixpict" modifier, which allows
to do exactly this. Only that since the Radiance picture format
doesn't include a seperate alpha channel, you'll have to code it
a little different than you might be used to from other software.The simplest way would be to create a seperate picture just
containing the alpha information. In a simple case like a
windowed wooden door, making all portions transparent where the
blue channel has a higher value than the red one might be a
useful workaround. Other methods will make sense in specific
situations.
>>I am experimenting with Desktop Radiance. Is the support for full face
>>textures something you'd care to make publicly available?Unfortunately, the Desktop Radiance binaries (technically: 3R3)
*don't* support the mixpict modifier. I am considering to offer
the Windows binaries as included in Rayfront for free download
seperately, which *do* support it. Other than Artifice, I am
licensed to distribute Radiance binaries, even If I have to keep
the sources closed (don't ask if this makes sense, just accept
it the way it is...).
>One would think that would be a good idea, and pretty natural for a company
>like Artifice that has invested significantly in other open source solutions.
>At the moment, unfortunately, it is not clear that Artifice is currently
>licensed to distribute changes to Radiance code. This is something we would be
>happy to work out with LBL, if they were motivated in the same direction.There is no problem for Artifice, or anyone else for that matter,
to publish *patches* to any of the unix versions of Radiance, so
that other users could apply the changes themselves. But I don't
think this is really necessary in this case. Unless I'm missing
something fundamental, everything asked for here is already
possible with the tools offered by Radiance, even if it requires
some creative function file tweaking.
>We really do love to give away software (whenever we can afford to...).
>However, we're not thrilled with what seems to be a heavy AutoCAD-specific
>focus in the Desktop Radiance development priorities. Unless I've missed
>something recently, LBL has not gone all the way to give Radiance a flexible
>open source license like the LGPL License used for Quesa -- and less so for
>Desktop Radiance.Give them a few more years... They *are* learning, they just
do it at their own pace.
Have fun!-schorsch