I have a problem; I don't have an image to hand to illustrate it but it's
easy to describe.

When rendering a Daz figure, converted from .obj with PoseRay, I've noticed
some shadow artifacts in the vicinity of the head that I don't understand.
Basically, the shadow of the head contains unlit areas which correspond to
the shadows of the eyes, eyelashes and eyebrows. I don't see how these
areas can be showing up because a) they should be opaque themselves, and b)
the rest of the head should also block this region.

I've had a hunt around in POV-Ray and PoseRay's docs but I can't find any
probable causes. Has anybody else noticed this, and if so, what's going
on!?

I'll try to post an example later this evening or tomorrow.

Bill

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Right. The problem definitely lies with transparency-mapped areas of the
mesh. The hair object exhibits the same behaviour. I still don't know what
to do about it though... :-(

Perplexed Bill

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Bill Pragnell <bil### [at] hotmailcom> wrote:
> Right. The problem definitely lies with transparency-mapped areas of the
> mesh. The hair object exhibits the same behaviour. I still don't know what
> to do about it though... :-(

  An image showing the problem could be of help.

-- 
                                                          - Warp

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Warp <war### [at] tagpovrayorg> wrote:
>   An image showing the problem could be of help.

Yes, sorry, of course!

http://www.infradead.org/~wmp/shadow_eg.jpg

Mind the nudity! (That'll get it some attention :-) )

Bill

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Bill Pragnell wrote:
> Warp <war### [at] tagpovrayorg> wrote:
>>   An image showing the problem could be of help.
> 
> Yes, sorry, of course!
> 
> http://www.infradead.org/~wmp/shadow_eg.jpg
> 

Bill,

I quickly created a similar scene and could not reproduce.

See this image:

http://mysite.verizon.net/sfg0000/files/DAZ_test.png

Can you tell me what type of lights did you use?

Does this problem occur with the default free Aiko skin?

What skin did you use? I may have it so I can test it here.

regards,

FlyerX

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FlyerX <fly### [at] yahoocom> wrote:
> http://mysite.verizon.net/sfg0000/files/DAZ_test.png

With my scene that would produce artifacts. I've had a little play and it
seems only to occur at certain angles, when the light is shining partly
across the face.

> Can you tell me what type of lights did you use?
A normal point-light.

> Does this problem occur with the default free Aiko skin?
I've seen it happen with the default skin too.

> What skin did you use? I may have it so I can test it here.
I can't remember where I got it, but I think the character's called
Daniella.

I should also mention that I've seen this occur in both POV-Ray 3.6 and
MegaPov 1.21. I think it must be something I'm doing (or not doing) during
the export / conversion process... what did you use to convert the mesh? I
used PoseRay.

Thanks
Bill

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web.454886817b19ba87731f01d10@news.povray.org...
>I have a problem; I don't have an image to hand to illustrate it but it's
> easy to describe.
>
> When rendering a Daz figure, converted from .obj with PoseRay, I've 
> noticed
> some shadow artifacts in the vicinity of the head that I don't understand.
> Basically, the shadow of the head contains unlit areas which correspond to
> the shadows of the eyes, eyelashes and eyebrows.

For what it's worth this drove me crazy when I worked on the "Reach for the 
stars" image. It's even mentioned in the "Making of". See the artifact under 
the kid's left eye: http://www.oyonale.com/iss/english/makingof_3.htm

I never found a solution, that's why the kid isn't facing the viewer in the 
final image... It's definitely related to a mixture of transparent and 
non-transparent zones in certain meshes, under certain lighting conditions.

G.



I don't see how these
> areas can be showing up because a) they should be opaque themselves, and 
> b)
> the rest of the head should also block this region.
>
> I've had a hunt around in POV-Ray and PoseRay's docs but I can't find any
> probable causes. Has anybody else noticed this, and if so, what's going
> on!?
>
> I'll try to post an example later this evening or tomorrow.
>
> Bill
>
>

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"Gilles Tran" <tra### [at] inapgfr> wrote:
> For what it's worth this drove me crazy when I worked on the "Reach for the
> stars" image. It's even mentioned in the "Making of". See the artifact under
> the kid's left eye: http://www.oyonale.com/iss/english/makingof_3.htm

That is helpful, actually. It proves (at least to my satisfaction) that it's
not something really obvious I'm doing wrong!

> I never found a solution, that's why the kid isn't facing the viewer in the
> final image... It's definitely related to a mixture of transparent and
> non-transparent zones in certain meshes, under certain lighting conditions.

Is there anything special about how POV-Ray calculates shadows for triangles
in mesh2s? In particular, are the triangles' inside/outside directions
important? Aside from the transparency mapping, these regions are also
unique because they are non-closed areas floating over the rest of the body
mesh. Just a thought.

Could it also be relevant that my Aiko is actually in a union? I must
experiment with the CSG aspect tonight.

I shall ruminate further
Bill

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Once I had similar artifacts (especially with the hair) when using DAZ figures.
As far as I remember (well, had no time for 'poving' since years) it had to do
with floating point (in)accuracy when using meshes with a scale like
1 PoV-unit = 1 m.
By scaling the mesh-figures (and of course the whole scene) in a way that
1 POV-unit equals 1 cm the artifacts went away.

Maybe you have the same problem...

regards
-Ive

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Bill Pragnell <bil### [at] hotmailcom> wrote:
> Could it also be relevant that my Aiko is actually in a union?

  I don't know if it has any effect on the rendering result, but if
you make it a mesh it will take less memory (and perhaps be a bit
faster to render).

  As someone suggested in another answer, try scaling the mesh (eg. 10 times
larger if the vertex values are very small, or 10 times smaller if the
vertex values are very large) to see if it helps. You'll have to do this
scaling in the modeller program. I'm not talking about the 'scale' keyword
in povray.

-- 
                                                          - Warp

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