"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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Warp <war### [at] tagpovrayorg> wrote:
>   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).
Agreed. I'm only using a union because she's holding something, and it makes
moving them both trivial.

>   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.
Rightyho. I can do that in DAZ studio. I shall try it this evening.

Bill

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Bill Pragnell <bil### [at] hotmailcom> wrote:
> Agreed. I'm only using a union because she's holding something, and it makes
> moving them both trivial.

  Well, just make a union of the two meshes, not a union of all individual
triangles.

-- 
                                                          - Warp

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Bill Pragnell wrote:
> 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
> 
> 

Bill,

I wrote PoseRay.

I tried a point light and still could not reproduce. I am using POV-Ray 
3.6 here. Check in the groups tab that the shadow is not turned off by 
mistake for any group. Shadow is toggled by clicking on the blue ball by 
the group name.

regards,

FlyerX

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FlyerX <fly### [at] yahoocom> wrote:
> I tried a point light and still could not reproduce.

  See if you can reproduce the problem by scaling the model down a lot
before exporting it (so that the vertex values being exported are very
small). The best theory so far is that this is what is causing the
problem.

-- 
                                                          - Warp

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Warp wrote:
> FlyerX <fly### [at] yahoocom> wrote:
>> I tried a point light and still could not reproduce.
> 
>   See if you can reproduce the problem by scaling the model down a lot
> before exporting it (so that the vertex values being exported are very
> small). The best theory so far is that this is what is causing the
> problem.
> 

I tried 0.1% scale and worked properly. At 0.001% most of the triangles 
were missing. But this does not match the original image from Bill where 
the shadow is broken but the model seems complete. For such large gaps 
the model would have visible tears in the mesh. Maybe is the small image 
and I can't see them.

For DAZ|Studio export the default Bryce preset should be used. Although 
I did not remember to update the PoseRay manual with the new DAZ Studio 
export dialog it does mention to export as a Bryce object.


FlyerX

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FlyerX <fly### [at] yahoocom> wrote:
> I tried 0.1% scale and worked properly. At 0.001% most of the triangles
> were missing. But this does not match the original image from Bill where
> the shadow is broken but the model seems complete. For such large gaps
> the model would have visible tears in the mesh. Maybe is the small image
> and I can't see them.
That sounds like a different problem. In my images, the lit areas correspond
exactly to the shadows of the eyes, eyebrows and eyelashes, although it's
not clear what's happening with the hair due to the complexity of that
object (I assume it's similar).
I didn't try scaling in the end, I was trying something else first, but I
had a look at the geom.inc file and all the vertex coodinates appear to be
between 0.0-1.0 and no more than 6 or 7 decimal places. I will try the
scaling trick just to make sure, but I don't think it's the culprit.

This doesn't shed any light on the phenomenon, but I have had partial
success in clearing the problem by exporting the eyes, eyebrows etc from
PoseRay as a separate mesh, and setting no_shadow for this object in
POV-Ray. I can't do this for the hair, however, so there are still a couple
of light patches at certain angles. This trick might have helped with the
kid in 'Reach for the Stars', I don't know.

> For DAZ|Studio export the default Bryce preset should be used. Although
> I did not remember to update the PoseRay manual with the new DAZ Studio
> export dialog it does mention to export as a Bryce object.
Hmm, I don't remember that... I'll have to have another look at the
DAZ|Studio end of business. But I won't hold my breath; Gilles said he had
the same problem using Poser (although I don't know if he used PoseRay or
not).

Anyway, I shall persevere. The scene's looking really nice; it's just this
mesh issue left to solve really... it's going to be a daylight version of
my IRTC entry in case anybody's curious.

Bill

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If you can somehow generate a minimal example (preferably with only part of
the full mesh needed) please either post a mention of it here or email me
about it.

-- Chris

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