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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Tue, 21 Jun 2005 03:44:05 GMT
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Viewed:
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1593 times
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In lugnet.cad, Don Heyse wrote:
> And I'm not sure I understand what you're saying about the linewidths.
Well, as you point out below, I was mostly wrong. However, I suspect it will
still produce jaggies on the inside edge of the lines (but I could be wrong).
These would almost certainly go away with 2-pixel edge lines. (These things are
very difficult to visualize.)
> :^) I use glPolygonOffset to make sure the lines get drawn over the
> polygons underneath. (Plus I cheat a bit and add a bit more z to
> antialiased edge lines so even skinny lines get drawn completely.) As
> far as I can tell even for skinny lines the AA partial coverage values
> extend beyond the pixels used to draw the unantialiased polygons so
> you do get something outside the polys even with the edge thickness
> set to 1. Think about it. We'd have no halo if the AA pixels exactly
> covered only the pixels drawn by the polygon pass. Unless you've been
> drawing the AA edge lines in the same pass as your opaque polygons.
> Blech!
You're right. But I still suspect the quality won't be as good this way as it
would be with the full blending and an opaque background. Hard to be sure
without trying it out.
> Yes, 2 passes only for the edge lines. I see you went with the
> blended ones first. That was my thought originally before I got
> sidetracked by the approach that doesn't use the stencil test.
> Personally I think the stencil test is better, but I wanted to mention
> both ways in case I come back here looking for a way to save on
> graphics memory for skimpier hardware.
Actually, I don't think the stencil buffer uses any memory on any existing
graphics hardware. It uses the last 8 bits of each 32-bit Z-buffer value, and
the Z-buffer only uses 24 bits. I'm not sure any cards support full 32-bit
Z-buffer, so if you don't use it for stencil, I don't think it gets used at all.
Having said that, stencil buffers aren't required to be hardware-accelerated.
So it's at least theoretically possible to have a video card that won't have a
hardware-accelerated mode with a stencil buffer. I suspect this doesn't happen,
though.
> Anyhow, You'll probably also want to disable writing to the alpha
> plane during the blended pass to preserve the 1's you wrote there
> during the polygon pass.
Yeah, that would probably be a good idea.
> So will there be an RC2?
I'm not sure yet. However, I can guarantee that this feature won't be in it if
there is one. I'm not adding any new features prior to the full 3.0 release.
--Travis
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Message is in Reply To:
 | | Re: White noise around model with colored background
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| (...) And I'm not sure I understand what you're saying about the linewidths. :^) I use glPolygonOffset to make sure the lines get drawn over the polygons underneath. (Plus I cheat a bit and add a bit more z to antialiased edge lines so even skinny (...) (19 years ago, 20-Jun-05, to lugnet.cad)
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