I am attempting to render gemstones with dispersion and have run into some
difficulties using PovRay v3.5.

In the finish statement I set the reflection color_reflection_min to the
square of (ior -1.0) / (ior + 1.0), the color_reflection_max to 1.0 and
turned on fresnel.

According to the help file when the amount of reflected light changes, the
amount of transmitted light should also change. To achieve this
conserve_energy keyword was added to the finish statement.

In the interior statement is the ior value and dispersion and its value.

When the gemstone is rendered there are hundreds of unwanted turquoise
colored spots.

How do I conserve energy and have dispersion without the turquoise spots?

Dick Conley
dic### [at] localaccesscom

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Dick Conley wrote:
> How do I conserve energy and have dispersion without the turquoise spots?

Increase photon_count or decrease photon_spacing?

-- 
--Tim Cook
http://empyrean.scifi-fantasy.com

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------

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So far I have had only one reply which did not solve the problem.

Further testing revealed that these turquoise spots are present with or
without photons when both conserve_energy and dispersion are present. Photon
spacing has no effect. With or without photons, remove either
conserve_energy or dispersion and the spots are gone.

With all the experts out there hopefully someone can show me how to have
conserve_energy and dispersion without the spots.

Dick Conley
dic### [at] localaccesscom


"Timothy R. Cook" <tim### [at] scifi-fantasycom> wrote in message
news:3e2b4635@news.povray.org...
> Dick Conley wrote:
> > How do I conserve energy and have dispersion without the turquoise
spots?
>
> Increase photon_count or decrease photon_spacing?
>
> --
> --Tim Cook
> http://empyrean.scifi-fantasy.com
>
> -----BEGIN GEEK CODE BLOCK-----
> Version: 3.12
> GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
> N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
> PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
> D++(---) G(++) e*>++ h+ !r--- !y--
> ------END GEEK CODE BLOCK------
>

Post a reply to this message

Dick Conley wrote:
> So far I have had only one reply which did not solve the problem.
> Further testing revealed that these turquoise spots are present with or
> without photons when both conserve_energy and dispersion are present. Photon
> spacing has no effect. With or without photons, remove either
> conserve_energy or dispersion and the spots are gone.
> With all the experts out there hopefully someone can show me how to have
> conserve_energy and dispersion without the spots.

Try increasing the dispersion count?  (hehe this one's probably
useless too, like my last one)

-- 
--Tim Cook
http://empyrean.scifi-fantasy.com

-----BEGIN GEEK CODE BLOCK-----
Version: 3.12
GFA dpu- s: a?-- C++(++++) U P? L E--- W++(+++)>$
N++ o? K- w(+) O? M-(--) V? PS+(+++) PE(--) Y(--)
PGP-(--) t* 5++>+++++ X+ R* tv+ b++(+++) DI
D++(---) G(++) e*>++ h+ !r--- !y--
------END GEEK CODE BLOCK------

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Is max_trace_level large enough? Is radiosity used? No coincident surfaces?

It might be easier to diagnose if a minimal scene is given so it can be
rendered by others.

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I forgot to uncomment conserve_energy before I sent the scene. Sorry.

You will need to uncomment conserve_energy to see the turquoise spots.

 Dick Conley
 dic### [at] localaccesscom

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Thanks for the files but you made a mistake by posting them into a
non-binaries group here at povray.general. You should have put them at
povray.binaries.scene-files. See the announce.f-a-q group for posting
guidelines.

Sorry if I misled you into thinking that attachments were okay here. To
cancel it in Outlook, select your message then go to the Message menu (main
menu), Cancel.

I'll be looking at the render and script to see if I can help.

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"Dick Conley" <dic### [at] localaccesscom> wrote in message
news:3e2b4240@news.povray.org...
> I am attempting to render gemstones with dispersion and have run into some
> difficulties using PovRay v3.5.
>
> When the gemstone is rendered there are hundreds of unwanted turquoise
> colored spots.
>
> How do I conserve energy and have dispersion without the turquoise spots?

Having now rendered your scene file I can only say that it seems a limit of
some kind is reached. I don't see anything like you describe though. What I
get is a charcoal diamond, shades of dark gray. When I lower ior to 1.5 a
portion in the middle turns white. I can't say it is a bug, only that it
looks like a limitation and could be a possible bug. To make matters worse
is that our renders do not show us the same thing occuring.

With any luck maybe someone else could tell more about this.

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It has been over 2 months, my problem has not been resolved and I have not
heard from anyone. Is this problem being investigated? Is there a problem
with PovRay? If PovRay is OK, what am I doing wrong? Would someone please
give me an update. It is frustrating waiting for answers and not knowing if
anything is being done to solve my problem.

Dick Conley
dic### [at] localaccesscom

"Dick Conley" <dic### [at] localaccesscom> wrote in message
news:3e2b4240@news.povray.org...
> I am attempting to render gemstones with dispersion and have run into some
> difficulties using PovRay v3.5.
>
> In the finish statement I set the reflection color_reflection_min to the
> square of (ior -1.0) / (ior + 1.0), the color_reflection_max to 1.0 and
> turned on fresnel.
>
> According to the help file when the amount of reflected light changes, the
> amount of transmitted light should also change. To achieve this
> conserve_energy keyword was added to the finish statement.
>
> In the interior statement is the ior value and dispersion and its value.
>
> When the gemstone is rendered there are hundreds of unwanted turquoise
> colored spots.
>
> How do I conserve energy and have dispersion without the turquoise spots?
>
> Dick Conley
> dic### [at] localaccesscom
>
>
>
>

Post a reply to this message

"Dick Conley" <dic### [at] localaccesscom> wrote in message
news:3e80aaf3$1@news.povray.org...
> It has been over 2 months, my problem has not been resolved and I have not
> heard from anyone. Is this problem being investigated? Is there a problem
> with PovRay? If PovRay is OK, what am I doing wrong? Would someone please
> give me an update. It is frustrating waiting for answers and not knowing if
> anything is being done to solve my problem.
>

Is this the same bug that's being discussed in "Bug with dispersion" in this
group? It does seem to be confirmed as a bug - perhaps a minimal scene that
demonstrates it and a post to bugreports?

BTW I'm sure it's not your intent, but your posts come across as rather bossy.

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