Subject:
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About the alpha-channel (was: Re: How is this created?)
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Newsgroups:
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lugnet.cad.mlcad
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Date:
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Wed, 22 May 2002 09:26:29 GMT
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Viewed:
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3028 times
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In lugnet.cad.mlcad, Ahui Herrera writes:
> When you convert a .ldr/.dat file to a .pov via L3PAO/L3P by default L3PAO
> put a floor plane in your model. That is say you render a 2x4 blue brick.
erm, hate to sound like a know-it-all (cos I don't know it all) but the
floor is a switch which isn't on by default. In L3P the switch to turn the
floor on is -F. In L3PAO it is a checkbox which you have to activate before
a floor is added.
> As for the alpha channel.. someone please tell us cause i have no clue on
> that one....
Sorry about that, but I cooked up a small tutorial.
On http://www.brickshelf.com/cgi-bin/gallery.cgi?i=175226 you see a
PowerPoint slide with a blue background. On it is placed a PNG-file with the
word "Tekst". This file doesn't have an alpha-channel. You can see a portion
of a screendump from Adobe Photoshop next to the Tekst-thingy. It shows the
composite RGB and all the individual channels (R, G and B).
On the next page ( http://www.brickshelf.com/cgi-bin/gallery.cgi?i=175227 )
an alpha channel is added to the RGB-file. The alpha channel in this case is
the word Tekst again. The white part in this channel will let the RGB
channels "shine thru" while the black parts will "stop" the RGB channel.
Sorry, I'm Dutch, and it is hard to explain. Simply said: White is opace and
black makes the picture translusant.
It isn't just a black and white thing (what is?). If you use shades of gray
the RGB picture becomes semi-translusant.
Try and experiment with it.
Oh, and I also put the original PPT-file on brickshelf so you can mess with
it for yourself! ( http://www.brickshelf.com/cgi-bin/gallery.cgi?i=175228 )
> > I render my instructions with LD-Lite and place the images with Microsoft
> > Publisher.
Sorry, I'm a MacUser. Don't have Publisher for the Macintosh so you'll have
to try. But if all Office applications support PNG-transparacy there is a
big chance Publisher will too.
Good luck making instructions, Jeroen (and sorry for the typos, no
zpelll-tjek in Internet Explorer)
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Message is in Reply To:
 | | Re: How is this created?
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| (...) When you convert a .ldr/.dat file to a .pov via L3PAO/L3P by default L3PAO put a floor plane in your model. That is say you render a 2x4 blue brick. If you look athe the POV code you will notice at the bottom a section of code that says (...) (22 years ago, 21-May-02, to lugnet.cad.mlcad)
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