Subject:
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Re: White noise around model with colored background
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Newsgroups:
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lugnet.cad
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Date:
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Wed, 8 Jun 2005 23:32:54 GMT
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Viewed:
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1400 times
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In lugnet.cad, Travis Cobbs wrote:
> In lugnet.cad, Don Heyse wrote:
> > I think I had an idea for an extra rendering pass to fix this but
> > never got motivated enough to try it out.
> >
> > http://news.lugnet.com/cad/dev/?n=9910
> >
> > Does it sound like it might work? I can barely remember what I was
> > thinking.
>
> That won't help. The problem is that OpenGL antialiasing antialises
> the color channel based on the background color the original rendering
> happens over. So even if you bump the alpha on all those pixels up to
> 1.0 (fully opaque), you'll still have the original blended color based
> on the original background color. You end up with the same problem
> with regular alpha-blended transparent items that sit over the
> background.
Ah ha! That explains why I said to set the background color to black.
That way the exterior lines alpha blend with zeros. I suspect setting
-b0 in the ldglite options window of lpub will give better results.
Maybe lpub should always do this if antialiasing and transparent pngs
are used.
> What we need is the ability to tell OpenGL to not blend the color
> channels if the destination alpha of the pixel being drawn is 0.
> (Perhaps the blending should be proportional to the destination
> alpha of the existing pixel.) I'm pretty sure this isn't possible
> in OpenGL.
Or we could blend with a background color of zero (black), right?
Enjoy,
Don
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Message has 1 Reply:
 | | Re: White noise around model with colored background
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| (...) Unfortunately, that doesn't help. It still blends, which means that if (for instance) your edge is red, and you have a pixel that's 50% covered via antialiasing, then that pixel comes out dark red (50% red + 50% black = dark red) with 50% (...) (19 years ago, 9-Jun-05, to lugnet.cad)
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Message is in Reply To:
| | Re: White noise around model with colored background
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| (...) That won't help. The problem is that OpenGL antialiasing antialises the color channel based on the background color the original rendering happens over. So even if you bump the alpha on all those pixels up to 1.0 (fully opaque), you'll still (...) (19 years ago, 8-Jun-05, to lugnet.cad)
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