kurtzlepirate-571F88.16540520022005@news.povray.org...

> any one can explain ?

A demonstration of the problem :

Antialiasing in 3.5
http://www.oyonale.com/temp/glass_demo_35.png

Antialiasing in 3.6
http://www.oyonale.com/temp/glass_demo_36.png

These images are rendered in regular POV-Ray using the same code. The 
lighting in the 3.6 version is much better due to the new unclipped 
radiosity values, and the sparkling on the glass is more realistic. However, 
the antialiasing around the bright pixels is just awful compared to the one 
in the 3.5 version.

G.


-- 
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters

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"Gilles Tran" <gitran_nospam_@wanadoo.fr> wrote in message
news:421bab2d@news.povray.org...

> kurtzlepirate-571F88.16540520022005@news.povray.org...
>
> > any one can explain ?
>
> A demonstration of the problem :
>
> Antialiasing in 3.5
> http://www.oyonale.com/temp/glass_demo_35.png
>
> Antialiasing in 3.6
> http://www.oyonale.com/temp/glass_demo_36.png
>
> These images are rendered in regular POV-Ray using the same code. The
> lighting in the 3.6 version is much better due to the new unclipped
> radiosity values, and the sparkling on the glass is more realistic. However,
> the antialiasing around the bright pixels is just awful compared to the one
> in the 3.5 version.

yes but, if I understand Warp correctly, it shouldn't be a problem to only do
pre-clipping with standard anti-aliasing.  I believe everybody agrees that
unclipped colors give better and more realistic results with radiosity (you just
gave an excellent example) and with focal-blur (I made an example once:
http://news.povray.org/povray.binaries.images/thread/%3C41d9ed03%40news.povray.o
rg%3E/?ttop=208966&toff=150), but I agree with Warp that with standard
anti-aliasing it causes more problems than it solves.  I don't believe going
back to pre-clipping is the right solution, but maybe color-bleeding is too
difficult to do.

cu!
--
camera{location-z*3}#macro G(b,e)b+(e-b)*(C/50)#end#macro L(b,e,k,l)#local C=0
;#while(C<50)sphere{G(b,e),.1pigment{rgb G(k,l)}finish{ambient 1}}#local C=C+1
;#end#end L(y-x,y,x,x+y)L(y,-x-y,x+y,y)L(-x-y,-y,y,y+z)L(-y,y,y+z,x+y)L(0,x+y,
<.5,1,.5>,x)L(0,x-y,<.5,1,.5>,x)               // ZK http://www.povplace.be.tf

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In povray.unofficial.patches Zeger Knaepen <zeger.knaepen@student.kuleuven.ac.be>
wrote:
> I don't believe going
> back to pre-clipping is the right solution, but maybe color-bleeding is too
> difficult to do.

  It might not be the best solution, but it's much better than the
post-clipped antialiasing.

  Color-bleeding is not difficult. Its problem is, however, that it's not
unambiguous. There are many ways of doing it and deciding which way is
correct and which parameters to give (or not give) the user to fine-tune
is problematic. It also basically requires adding a post-processing step
to POV-Ray, which is a whole new world and should be done hastily and
without thought.

-- 
plane{-x+y,-1pigment{bozo color_map{[0rgb x][1rgb x+y]}turbulence 1}}
sphere{0,2pigment{rgbt 1}interior{media{emission 1density{spherical
density_map{[0rgb 0][.5rgb<1,.5>][1rgb 1]}turbulence.9}}}scale
<1,1,3>hollow}text{ttf"timrom""Warp".1,0translate<-1,-.1,2>}//  - Warp -

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> post-processing step to POV-Ray, which is a whole new world and should
> be done hastily and without thought.

I agree. Only minor changes should be thought about and carefully
implemented: big stuff should just be run off in half an hour when
you're bored.

Or maybe there should have been a "not" in that sentence :->

Daniel

-- 
I went to the CO guess what he told me guess what he told me | apologies
He said  boy u better learn to like Win  no matter what u do | to Prince
But  he's  a  fool,  'cos  nothing  compares,  nothing  compares  2  GNU
http://surreal.istic.org/ | A tidy desk is the product of an empty mind.

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In povray.unofficial.patches Daniel Hulme <photoreal@istic.org> wrote:
> Or maybe there should have been a "not" in that sentence :->

  Nah... ;)

-- 
#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 <war### [at] tagpovrayorg> wrote:
>   Post-clipped antialiasing causes problems in a multitude of images
> very frequently. You only have to have a surface which is much brighter
> than 1 and a sharp edge adjacent to a dimmer surface (which is quite
> a common situation) to get ugly pixelation of the edge. Pixels much
> brighter than 1 are completely normal, not modelling flaws.
>   Just look at The Kitchen image carefully to see the ugly post-clipping
> artifacts (these were not taken into account in judging because it
> was decided that these artifacts can be got ridden of in future
> versions of POV-Ray).

Thank you.  That explains something I saw and thought was some sort of a bug
involving 3.6 and blobs (since that's where I happened to see the problem
in my case.)  Aparently, though, it's caused by post-clipped antialiasing,
since the problem occurs at a place where reflections and specularity
combine to get very bright pixels.  I tried upping max_trace_level,
cranking anti-alias down to 0 -- finally decided to just use the picture I
made with 3.5.

Dave Matthews

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Has this been resolved yet, or do we still use 3.5 for better antialiasing?
I just noticed that my IRTC entry has jaggies when rendered in 3.6 vs. 3.5.
Oh well.

"Dave Matthews" <dma### [at] wrmnwestmnscuedu> wrote:
> Warp <war### [at] tagpovrayorg> wrote:
> >   Post-clipped antialiasing causes problems in a multitude of images
> > very frequently. You only have to have a surface which is much brighter
> > than 1 and a sharp edge adjacent to a dimmer surface (which is quite
> > a common situation) to get ugly pixelation of the edge. Pixels much
> > brighter than 1 are completely normal, not modelling flaws.
> >   Just look at The Kitchen image carefully to see the ugly post-clipping
> > artifacts (these were not taken into account in judging because it
> > was decided that these artifacts can be got ridden of in future
> > versions of POV-Ray).
>
> Thank you.  That explains something I saw and thought was some sort of a bug
> involving 3.6 and blobs (since that's where I happened to see the problem
> in my case.)  Aparently, though, it's caused by post-clipped antialiasing,
> since the problem occurs at a place where reflections and specularity
> combine to get very bright pixels.  I tried upping max_trace_level,
> cranking anti-alias down to 0 -- finally decided to just use the picture I
> made with 3.5.
>
> Dave Matthews

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