Kari Kivisalo wrote:

> 
> Currently this is the best povray can do (+a0.0 +r9). Notice
> the aliasing artefacts on the horizontal lines.
> http://luxlab.com/tmp/aa.png
> 
> Rendered at 500% resolution (+a0.3 +r3), low-pass filtered
> (Gaussian 2.5 pixels) and resampled.
> http://luxlab.com/tmp/aa_hq.png
> 
> I like the one with clean lines.
> 

Looks really smooth. But I think it makes the lines also appear thicker 
than they are. You get a similar result when you just 'blur' the texture in 
POV-Ray and then use the normal aa method without oversizing and scaling:

pigment{gradient y
        pigment_map{
        [0 rgb 1]
        [0.41 rgb 1]
        [0.5 rgb 0.3]
        [0.59 rgb 1]
        }
}

However the bluring would have to be done dependend on the distance to 
remove the artifacts in the mid-distance.

Maybe one could add a 'blur texture when far away'-feature to POV.

- Micha

-- 
objects.povworld.org - The POV-Ray Objects Collection
book.povworld.org    - The POV-Ray Book Project

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> The most important part is the Gaussian blur. I used 500% resolution
> just to get those very thin lines. For normal a scene 200% to 300% and
> 1 to 1.5 pixel blur radius should be enough. The 50% blur radius seemed
> to be the minimum required to prevent visible aliasing. The image will
> look soft. Sharpening filter will just bring back the the jagged edges.
> It's a delicate balance between artefect free and sharp image :)
>
>
> _____________
> Kari Kivisalo

I made some experiments with your method this afternoon.
It is much better than my method, which I used in my two last IRTC entries.
I will no more use normal POV-Ray antialiasing, as such methods show enhance
most pictures considerably.
As an added benefit you get an high res version for printing at the same
time.

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"Norbert Kern" wrote:
> I made some experiments with your method this afternoon.
> It is much better than my method, which I used in my two last IRTC entries.
> I will no more use normal POV-Ray antialiasing,

Me too. And it seems to work well even with non antialiased pics.

--
Jonathan.

Home: http://digilander.iol.it/jrgpov

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Micha Riser wrote:
>
> But I think it makes the lines also appear thicker
> than they are.

Which brings us to the question of optimal sampling filter
for 2D signal. My theory is that the artefacts in the default
povray aa and mosaic filtered image appear because the sampling
filter is a rigid box. This produces a ringing efect. This can
be avoided by sacrificing higher frequencies and using a smooth
edged filter.

This increases noise but reduces sampling artefacts:
+am1 +a0.0 +r9 +j13.5

It's always a trade-off :(


_____________
Kari Kivisalo

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Norbert Kern <nor### [at] t-onlinede> wrote:
> It is much better than my method, which I used in my two last IRTC entries.
> I will no more use normal POV-Ray antialiasing, as such methods show enhance
> most pictures considerably.

  I don't think you can do that with an IRTC entry. The rules prohibit
post-processing.

-- 
#macro N(D)#if(D>99)cylinder{M()#local D=div(D,104);M().5,2pigment{rgb M()}}
N(D)#end#end#macro M()<mod(D,13)-6mod(div(D,13)8)-3,10>#end blob{
N(11117333955)N(4254934330)N(3900569407)N(7382340)N(3358)N(970)}//  - Warp -

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Warp wrote:
>
>   I don't think you can do that with an IRTC entry. The rules prohibit
> post-processing.

Do they prohibit anti-aliasing or resampling? This is just advanced aa.
Or if that doesn't fly, then it's per pixel weighted average contrast
adjustment :)


_____________
Kari Kivisalo

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+am1 +a0.0 +r9 +j13.5

http://luxlab.com/tmp/aa_noise.png


_____________
Kari Kivisalo

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"Warp" <war### [at] tagpovrayorg> schrieb im Newsbeitrag
news:3ca8be48@news.povray.org...

>   I don't think you can do that with an IRTC entry. The rules prohibit
> post-processing.

I should quote the rules:
http://www.irtc.org/stills/faq.html#q1.1.11

[1.1.11] Exactly what do you mean by "post-processing"?

"One guideline that has been mentioned is that
any process which affects every pixel in the image is usually okay,
but that's not a hard and fast rule--it's just used to encompass gamma
correction, resizing, conversion to JPEG format, and so forth, all of
which are legal."

I see application of the method as a special form of image resizing, which
is certainly allowed.


Norbert

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Kari Kivisalo <pro### [at] luxlabcom> wrote:
> Do they prohibit anti-aliasing or resampling? This is just advanced aa.
> Or if that doesn't fly, then it's per pixel weighted average contrast
> adjustment :)

  It is post-processing in an extent prohibited by the rules. I don't see
any rule allowing resizing the rendered image.
  If that would be allowed, what else? Some filtering? Blurring?
Stylisizing? Lens flares?

  No, the rules don't allow that kind of post-processing, period.

-- 
#macro M(A,N,D,L)plane{-z,-9pigment{mandel L*9translate N color_map{[0rgb x]
[1rgb 9]}scale<D,D*3D>*1e3}rotate y*A*8}#end M(-3<1.206434.28623>70,7)M(
-1<.7438.1795>1,20)M(1<.77595.13699>30,20)M(3<.75923.07145>80,99)// - Warp -

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"Warp" <war### [at] tagpovrayorg> schrieb im Newsbeitrag
news:3ca8e4d2@news.povray.org...

>   It is post-processing in an extent prohibited by the rules. I don't see
> any rule allowing resizing the rendered image.
>   If that would be allowed, what else? Some filtering? Blurring?
> Stylisizing? Lens flares?
>
>   No, the rules don't allow that kind of post-processing, period.

resizing is allowed :

http://www.irtc.org/stills/faq.html#q1.1.14

[1.1.14] Is it legal to resize my image after it is rendered?
Yes, it is. Be careful doing it, though--unless done correctly, resizing can
often add unwanted visual artifacts to an image.

Norbert

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