POV-Ray : Newsgroups : povray.beta-test : Black outline in smooth meshes Server Time
30 Jul 2024 12:24:54 EDT (-0400)
  Black outline in smooth meshes (Message 1 to 7 of 7)  
From: Gilles Tran
Subject: Black outline in smooth meshes
Date: 17 Nov 2001 09:50:54
Message: <3bf6794e$1@news.povray.org>
The outline of smooth meshes exhibit black dots or areas. Apart setting a
high ambient value, I haven't found a way to make them disappear.
This is of course related to the fact that smoothness is simulated. Another
related artefact is that facets can be visible too. However, while the facet
problem mostly goes away when the resolution of the mesh is increased, the
black outline problem can be quite visible even with hi-res meshes. It can
become very annoying when the mesh has a light texture (such as skin) and is
set on a light background. I had to touch up images a few times due to this
: artefacts that were lost in the antialisasing at 800x600 became
conspicuous at higher image sizes. The editing is not very easy either, as
the dots are pure black.

See the examples in beta-test.binaries. One is with a low-res mesh sphere,
the other with a high-res mesh sphere.

This is an old problem, so bringing it up at this stage here may seem quite
late or even unappropriate. Anyway, as it's likely that 3.5 users will use
meshes more often, I wonder whether there could be fix (or at least
workaround) for it.

G.

--

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


Post a reply to this message

From: JRG
Subject: Re: Black outline in smooth meshes
Date: 17 Nov 2001 10:21:00
Message: <3bf6805c@news.povray.org>
I may be wrong, but isn't it the famous shadow line problem? IIRC Alan
Holding found a workaround: use two copies of the same mesh: one with the
no_shadow flag and the other one with no_image and no_reflection.

--
Jonathan.

"Gilles Tran" <tra### [at] inapginrafr> ha scritto nel messaggio
news:3bf6794e$1@news.povray.org...
> The outline of smooth meshes exhibit black dots or areas. Apart setting a
> high ambient value, I haven't found a way to make them disappear.
> This is of course related to the fact that smoothness is simulated.
Another
> related artefact is that facets can be visible too. However, while the
facet
> problem mostly goes away when the resolution of the mesh is increased, the
> black outline problem can be quite visible even with hi-res meshes. It can
> become very annoying when the mesh has a light texture (such as skin) and
is
> set on a light background. I had to touch up images a few times due to
this
> : artefacts that were lost in the antialisasing at 800x600 became
> conspicuous at higher image sizes. The editing is not very easy either, as
> the dots are pure black.
>
> See the examples in beta-test.binaries. One is with a low-res mesh sphere,
> the other with a high-res mesh sphere.
>
> This is an old problem, so bringing it up at this stage here may seem
quite
> late or even unappropriate. Anyway, as it's likely that 3.5 users will use
> meshes more often, I wonder whether there could be fix (or at least
> workaround) for it.
>
> G.
>
> --
>
> **********************
> http://www.oyonale.com
> **********************
> - Graphic experiments
> - POV-Ray and Poser computer images
> - Posters
>
>
>


Post a reply to this message

From: Gilles Tran
Subject: Re: Black outline in smooth meshes
Date: 17 Nov 2001 11:14:28
Message: <3bf68ce4$1@news.povray.org>

3bf6794e$1@news.povray.org...
> The outline of smooth meshes exhibit black dots or areas. Apart setting a
> high ambient value, I haven't found a way to make them disappear.

Found one : double_illuminate fixes it, at least on closed meshes.

G.


--

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


Post a reply to this message

From: Gilles Tran
Subject: Re: Black outline in smooth meshes
Date: 17 Nov 2001 11:14:31
Message: <3bf68ce7$1@news.povray.org>

3bf6805c@news.povray.org...
> I may be wrong, but isn't it the famous shadow line problem? IIRC Alan
> Holding found a workaround: use two copies of the same mesh: one with the
> no_shadow flag and the other one with no_image and no_reflection.

IIRC the shadow line problem consists in having a harsh shadow terminator on
an object where the transition should be smooth (happens when normals are
used). The no_shadow object looks better but doesn't project a shadow so the
no_image object provides the shadow.
I've just tried this on the black outline problem. Interestingly, the facet
problem goes away... and the outline in the unlit part is now white instead
of black !!!

... but it seems that double_illuminate fixes the problem.

G.



--

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

> --
> Jonathan.
>


Post a reply to this message

From: JRG
Subject: Re: Black outline in smooth meshes
Date: 17 Nov 2001 13:55:04
Message: <3bf6b288$1@news.povray.org>
Gilles Tran
> ... but it seems that double_illuminate fixes the problem.

That would bring me to think that at shallow angles normals are somehow
inverted...

--
Jonathan.


Post a reply to this message

From: Warp
Subject: Re: Black outline in smooth meshes
Date: 17 Nov 2001 18:45:35
Message: <3bf6f69f@news.povray.org>
Gilles Tran <tra### [at] inapginrafr> wrote:
: Found one : double_illuminate fixes it, at least on closed meshes.

  Perhaps this is the reason why smooth meshes were double-illuminated
in pov3.1?

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -


Post a reply to this message

From: Gilles Tran
Subject: Re: Black outline in smooth meshes
Date: 18 Nov 2001 12:48:06
Message: <3bf7f456$1@news.povray.org>

3bf6f69f@news.povray.org...
> Gilles Tran <tra### [at] inapginrafr> wrote:
> : Found one : double_illuminate fixes it, at least on closed meshes.
>   Perhaps this is the reason why smooth meshes were double-illuminated
> in pov3.1?

The problem was already in 3.1 (I tested again to be sure). I'm quite sure
to have seen this problem reported before (and before 3.5).

G.

--

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


> --
> #macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
> rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
> ],13),8)-3,10>#end blob{N(array[6]{11117333955,
> 7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -


Post a reply to this message

Copyright 2003-2023 Persistence of Vision Raytracer Pty. Ltd.