Jeremy M. Praay wrote:
> Unfortunately, it appears that there is no simple solution (unless you
> consider post-processing to be a solution).
> 
> I came across this article which describes exactly the problem that I'm
> having, and now I'm slightly depressed:
> http://tag.povray.org/povQandT/TheShadowLineArtifact/index.html
> 
It's a little discouraging.  Another answer, possibly, is to to get a 
little more familiar with mesh editing tools and what free editors are 
available that will load Poser .obj files ( Wings will sometimes, but 
not reliably ) and just subdivide and smooth the ***p out of the model 
before converting to SDL.  I mean what's the alternative, to not make 
the picture you want?

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"Jim Charter" <jrc### [at] msncom> wrote in message
news:40bd1e5e$1@news.povray.org...
> Jeremy M. Praay wrote:
> > Unfortunately, it appears that there is no simple solution (unless you
> > consider post-processing to be a solution).
> >
> > I came across this article which describes exactly the problem that I'm
> > having, and now I'm slightly depressed:
> > http://tag.povray.org/povQandT/TheShadowLineArtifact/index.html
> >
> It's a little discouraging.  Another answer, possibly, is to to get a
> little more familiar with mesh editing tools and what free editors are
> available that will load Poser .obj files ( Wings will sometimes, but
> not reliably ) and just subdivide and smooth the ***p out of the model
> before converting to SDL.  I mean what's the alternative, to not make
> the picture you want?

Yeah, maybe I'll try subdividing.  Mostly, I was just playing around, but I
got a simple scene in my head, and thought I'd see how it worked.  Harsh
shadows were part of the effect that I wanted.  *sigh*

-- 
Jeremy
www.beantoad.com

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"Alain" <aze### [at] qwertygov> wrote in message
news:40bd0deb$1@news.povray.org...

> You may try enlarging the area light. It /may/ aleviate your problem by
> making the shadow line fuzyer, possibly making the artifact less
> visible. Try ading a dim and tight spot light to get some extra light
> near the problem spot (you may need as many as there are artifacts).
> Using radiosity, a white box behind and to a side of the camera can give
> some extra light where needed. Make that box large enough so that it can
> have a significant contribution. It may need some ambient greater than 0
> or a diffuse >1. Not aplicable if there is a mirror showing that area.
> Those are tentative suggestions and may be counter indicated for your
sene.
>

Using a larger area light does lessen the problem, but it's still there.
BTW, I tried POV 3.6 beta also.  Maybe POV-Ray 4.0 (or 4.5 or 5.0) will fix
it.

Oh well...  I was trying to do a somewhat tasteful nude scene, which I'd
probably be rather reluctant to display publicly anyway.  ;-)  But in all
seriousness, finding good Poser clothes is difficult, making your own is
even harder, and getting the clothes to look good in a POV-Ray picture is
harder still.  But I've ranted about that before...

-- 
Jeremy
www.beantoad.com

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Jeremy M. Praay wrote:


> Oh well...  I was trying to do a somewhat tasteful nude scene, which I'd
> probably be rather reluctant to display publicly anyway.  ;-) 

It'd be OK, as long as you post it in JPEG2000 ;-)

Dave Matthews

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"Dave Matthews" <nos### [at] nospamedu> wrote in message
news:40be0e11@news.povray.org...
>
> It'd be OK, as long as you post it in JPEG2000 ;-)
>

LOL!

It makes me think that at some point in the future, someone is going to read
that post, and not having been here a month ago, they'd have no idea what
you were talking about.  "It's ok to post nudes only in JPEG2000 format?
How strange..."  ;-)  I never did figure out how to see his "hidden image"
trick using color palette manipulation, but I suppose I could do that too...

-- 
Jeremy
www.beantoad.com

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Jeremy M. Praay wrote:

> I came across this article which describes exactly the problem that I'm
> having, and now I'm slightly depressed:
> http://tag.povray.org/povQandT/TheShadowLineArtifact/index.html

I've had that problem with height_fields and some meshes from other 
modellers, but never had that on a poser figure before. What did you use 
to convert to Pov?

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news:40bbaa3d$1@news.povray.org...
>
> Does anyone have any more helpful hints?

Photoshop...

There are several issues with meshes in POV-Ray and this is one of them...
and not the worst. At least black triangles can be photoshoped away.
Subdividing is a solution but then it's not always possible to keep the uv
vectors (Cinema 4D can do that but it's not exactly free). Christophe
Bouffartigue once made a patch that seemed to fix this problem.

Here are other issues you will meet at one time or another:

- using high radiosity settings on multi-layered, semi-transparent meshes
(such as hair) tend to darken them, sometimes turning the texture into pure
black. I never found a solution for this.

- under certain lighting conditions, interactions between parts of the mesh
give ugly results: lighting artifacts start shining through the edges of the
triangles (nice cracking effect) or in other places. Particularly, I have
ongoing problems with the eyebrows and lashes when used with certain hair
models in Millenium figures. I sometimes use uvmapper to remove eyebrows and
lashes, which fixes it but isn't a good solution for close-ups. This is why
the kid in the "Reach of the stars" picture is seen from behind...

-in Pov-Ray 3.5 using meshes and reflections can sometimes end up in an
infinite loop (a real plague when I was working on the WTC memorial
project). This seems to be fixed in 3.6 though.

G.

-- 

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

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"Gilles Tran" <tra### [at] inapginrafr> wrote in message
news:40c05c9e$1@news.povray.org...
>
> There are several issues with meshes in POV-Ray and this is one of them...
> and not the worst. At least black triangles can be photoshoped away.
> Subdividing is a solution but then it's not always possible to keep the uv
> vectors (Cinema 4D can do that but it's not exactly free). Christophe
> Bouffartigue once made a patch that seemed to fix this problem.
>

Ahhh... yes...  I did some Googling and came across this discussion from 2
years ago:

http://news.povray.org/povray.beta-test/thread/%3C3cf448cd@news.povray.org%3E/

I haven't tried it in MegaPov 1.0, but since it was a complete rewrite using
the 3.5 source, it's probably quite likely that the patch isn't there.

> Here are other issues you will meet at one time or another:
>
> - using high radiosity settings on multi-layered, semi-transparent meshes
> (such as hair) tend to darken them, sometimes turning the texture into
pure
> black. I never found a solution for this.

Yes, I've come across that.  I thought it was something stupid that I was
doing, but eventually my scenes get so complex that I have to turn down
radiosity settings anyway.  Well, that, and I spend a lot of time doing
outdoors scenes, which generally don't need much radiosity.

>
> - under certain lighting conditions, interactions between parts of the
mesh
> give ugly results: lighting artifacts start shining through the edges of
the
> triangles (nice cracking effect) or in other places. Particularly, I have
> ongoing problems with the eyebrows and lashes when used with certain hair
> models in Millenium figures. I sometimes use uvmapper to remove eyebrows
and
> lashes, which fixes it but isn't a good solution for close-ups. This is
why
> the kid in the "Reach of the stars" picture is seen from behind...
>
> -in Pov-Ray 3.5 using meshes and reflections can sometimes end up in an
> infinite loop (a real plague when I was working on the WTC memorial
> project). This seems to be fixed in 3.6 though.
>

I haven't come across those other issues, but thanks or mentioning them. It
will probably save me hours of trouble-shooting in the future.

I really hope that at some point someone can address the "smooth triangle
artifact" problem.  Now that I'm aware of it, I've noticed that it pops up
all over the place in other people's images.  As meshes become more and more
prevalent in POV-Ray pictures (which seems to be the trend for many of us),
this issue will probably become more of an annoyance.

To avoid problems that I've encountered with normals on CSG surfaces, I
generally try to use iso-surfaces when I can.  At the risk of sounding like
a complete buffoon, I have to ask if anyone has ever tried converting smooth
triangle meshes to bi-cubic patches?  It would certainly take care of this
problem, but my guess is that render times would go through the roof, and it
might produce some other problems as well.  But we've certainly seen
utilities that do the opposite (e.g. hamapatch).  It's easy for me to deal
in the theoretical, since I have very little idea of how this stuff actually
works.

-- 
Jeremy
www.beantoad.com

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"Jeremy M. Praay" <jer### [at] questsoftwarecom> wrote in message
news:40c0888e@news.povray.org...
>
> At the risk of sounding like
> a complete buffoon, I have to ask if anyone has ever tried converting
smooth
> triangle meshes to bi-cubic patches?

Apparently, POV-Ray converts bicubic patches to triangles with normals
applied, according to the docs, so I guess that would be a worthless
endeavor.

-- 
Jeremy
www.beantoad.com

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"Jeremy M. Praay" <jer### [at] questsoftwarecom> wrote in message
news:40c0888e@news.povray.org...
> "Gilles Tran" <tra### [at] inapginrafr> wrote in message

> > - using high radiosity settings on multi-layered, semi-transparent
meshes
> > (such as hair) tend to darken them, sometimes turning the texture into
> pure
> > black. I never found a solution for this.

> Yes, I've come across that.  I thought it was something stupid that I was
> doing, but eventually my scenes get so complex that I have to turn down
> radiosity settings anyway.  Well, that, and I spend a lot of time doing
> outdoors scenes, which generally don't need much radiosity.

Me too, I'm doing some outdoor scenes on Mars and have some semi-decent
looking hair, and haven't run into this.  Then again, I'm using the defautl
radiosity settings from Moray.  It sounds like I've just been lucky.

> I really hope that at some point someone can address the "smooth triangle
> artifact" problem.  Now that I'm aware of it, I've noticed that it pops up
> all over the place in other people's images.

I ran into with my terrain meshes - I'm using a lot of height fields and
sometimes get black triangles.  My Mars landscapes aren't terribly
reflective, though, so I don't seem to have as much trouble as others have
had.  Will post some images eventually, although my tank tread image in
P.B.I was done with radiosity and height fields.

> As meshes become more and more
> prevalent in POV-Ray pictures (which seems to be the trend for many of
us),
> this issue will probably become more of an annoyance.

Right!

I'm using CSG on my height fields though, which I think might make it easier
to use bump maps at least with these, it's not a pure mesh.  From reading
the description of the problem from the link you gave, it sounds like the
problem could be fixed by an 'inside'.  Is that possible?

> To avoid problems that I've encountered with normals on CSG surfaces, I
> generally try to use iso-surfaces when I can.  At the risk of sounding
like
> a complete buffoon, I have to ask if anyone has ever tried converting
smooth
> triangle meshes to bi-cubic patches?  It would certainly take care of this
> problem, but my guess is that render times would go through the roof, and
it
> might produce some other problems as well.  But we've certainly seen
> utilities that do the opposite (e.g. hamapatch).  It's easy for me to deal
> in the theoretical, since I have very little idea of how this stuff
actually
> works.

Interesting idea - at least for Poser models, I'd like to actually use some
real displacment mapping, but of course that brings up the whole
'displacement mapping with ray tracer' flame thing.

Poser5 has some nice effects you can do with real displacement maps, instead
of bump maps.  I'd prefer to make use of this instead of actual bump maps
for larger displacements, but bump maps can be effective for small things
like pores and fine wrinkles, that really aren't 'displaced' much at normal
resolutions.

        == John ==

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