POV-Ray : Newsgroups : povray.binaries.images : Sample scene ideas : Re: Sample scene ideas Server Time
20 Oct 2021 14:40:12 EDT (-0400)
  Re: Sample scene ideas  
From: clipka
Date: 27 Jun 2021 21:31:50
Message: <60d92686$1@news.povray.org>
Am 28.06.2021 um 02:17 schrieb Bald Eagle:

> _I_ can detect it at 100%, I don't think I'm completely imagining some sort of
> issue at 200%, and at 500%, that first "N" is an atrocity, and "f" is not
> looking good either...

My guess is that what you're unhappy with are just the artifacts 
generated by `+am3`.

Anti-aliasing mode 3 is noisy by nature, as it uses pseudo-random jitter 
across the entire pixel for supersampling.


Some of your other anti-aliasing settings exacerbate the problem:

`+r2` means you get at most 16 rays, which tends to be not a lot for 
sharp contrasts. Using a higher value will not give you totally crisp 
edges, but less noisy ones.

`+ag1` means you tend to get unnecessarily poor performance for 
comparatively bright areas and unnecessarily poor quality in 
comparatively dark ones. Note that `+agN` is NOT the space in which 
averages are computed - that's always done in linear space - but rather 
the space in which the threshold (`+a0.001`) is applied. A setting of 1, 
i.e. linear gamma space, means the threshold allows for _physically_ 
identical maximum errors in regions of any brightness, but 
_perceptually_ those maximum errors are more obvious in low-brightness 
regions of the image than in high-brightness regions. Leaving it set to 
the default of 2.5 causes POV-Ray to accept _perceptually_ similar 
maximum errors regardless of absolute brightness. I strongly recommend 
leaving it at the default unless you have very compelling reasons not to 
(*).

`+acN` is missing from your settings entirely, although it is one of the 
key settings for balancing performance vs. quality in mode 3.

`-j` doesn't hurt, but is completely ignored in mode 3. That mode is 
jitter pure. (It may be argued that POV-Ray should possibly issue a 
warning when faced with such a contradictory setting.)

(`+a0.001` is fine, no issue there. You could probably get away with a 
higher value - `+a0.004` should be perfectly fine, maybe even `+a0.01`.)


(*A valid use case for `+ag1` would be if you tried to compute a depth 
map rather than actual colors, and wanted the same absolute precision at 
all distances within the range.)


>> As for the increase in thickness, it causes the text at the left and
>> right to appear more "bold" because we're seeing it stretch
>> perspectively "into the image", but it inevitably leaves the center
>> portion of the text as "unbold" as ever.
> 
> Yes, I understand that - aside from scaling perpendicular to the viewing axis,
> there's likely not a viable way to bolden text aside from changing over to
> another font.   But it's a sample scene, so I'm trying to stick with the 3 fonts
> that we ship with.

You could use two copies of the text object, and offset one of them 
horizontally by a tiny value. That should bolden the vertical stems.


> Maybe I'll just scale x*1.something and see if that's good 'nuff.

You mean to shoo away the artifacts you're describing? It would be 
surprising if it made any difference.

As for using this approach to bolden the text - it would widen the 
vertical stems, but it wouldn't increase the overall "weight" of the font.


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