POV-Ray : Newsgroups : povray.binaries.images : Another Photon Bug? Server Time
30 Jul 2024 10:20:27 EDT (-0400)
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From: James Holsenback
Subject: Re: Another Photon Bug?
Date: 24 Sep 2012 07:50:25
Message: <50604901$1@news.povray.org>
On 09/24/2012 12:20 AM, Ive wrote:

> Err, sorry, this was out of my head and has the usual bugs.

no worries ... saw and fixed those last evening


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From: James Holsenback
Subject: Re: Another Photon Bug?
Date: 24 Sep 2012 07:52:19
Message: <50604973$1@news.povray.org>
On 09/24/2012 05:27 AM, clipka wrote:
> Am 24.09.2012 00:59, schrieb Ive:
>
>> Attached is a quick lo-quality (90 seconds) preview render - not a
>> spectral one - featuring your stone: from left to right emerald,
>> sapphire and amethyst.
>
> Looking forward to see a spectral render... you're gonna do one, right?

lol ... hadn't considered that ... maybe i will give it a try


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From: MichaelJF
Subject: Re: Another Photon Bug?
Date: 12 Oct 2012 12:45:00
Message: <web.50784899682ec91728c1b9ac0@news.povray.org>
Ive <ive### [at] lilysoftorg> wrote:
> #macro M_Gem (Color, IOR, FadeDist)
>    material {
>      texture {
>        pigment {rgb Color filter 1}
>        finish {
>          ambient 0  emission 0  diffuse 0
>          reflection {0 1 fresnel on} conserve_energy
>        }
>      }
>      interior {
>        ior IOR
>        fade_power 1001
>        fade_distance FadeDist
>        fade_power rgb < pow(Color.red,3),
>                         pow(Color.green,3)
>                         pow(Color.blue,3) >
>      }
>    }
>
> #end
Seems I have missed this discussion about gems due to RL issues. Your main idea
seems to be to use the interior with fade_color to color the stones. I used a
similiar approach for my stone of orloff mainly derived from a macro given by
Bruno Cabasson. I only wonder about the pow(x,3). You have given the colors used
in a later posting. Since this were floats you could even used the
pow(x,3)-values instead. Is it due to a color space conversion? I'm puzzled.

Best regards,
Michael


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From: Ive
Subject: Re: Another Photon Bug?
Date: 13 Oct 2012 02:43:59
Message: <50790daf@news.povray.org>
Am 12.10.2012 18:43, schrieb MichaelJF:
> Seems I have missed this discussion about gems due to RL issues. Your main idea
> seems to be to use the interior with fade_color to color the stones. I used a
> similiar approach for my stone of orloff mainly derived from a macro given by
> Bruno Cabasson. I only wonder about the pow(x,3). You have given the colors used
> in a later posting. Since this were floats you could even used the
> pow(x,3)-values instead. Is it due to a color space conversion? I'm puzzled.
>
> Best regards,
> Michael
>

The colors given in my reply to James are calculated from the absorbing 
spectrum of the "real" objects. Note that I do use the same color (and 
not ^3) within the pigment statement and this has influence on the final 
appearance even with ambient and diffuse = 0.

And BTW here are two colors calculated from spectral data of two typical 
diamonds:

Diamond ("natural yellow") : rgb <0.9856, 0.9924, 0.8726>
Diamond ("lemon yellow")   : rgb <0.9909, 0.9697, 0.8961>

-Ive


P.S. sorry for the mail, since T'birds user interface has changed it 
happens to me all the time :(


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From: MichaelJF
Subject: Re: Another Photon Bug?
Date: 14 Oct 2012 14:00:01
Message: <web.507afcf0682ec9173b8eee5f0@news.povray.org>
Ive <ive### [at] lilysoftorg> wrote:

> P.S. sorry for the mail, since T'birds user interface has changed it
> happens to me all the time :(
Of course I was puzzled again and tried to answer you in private. But since my
Mail-System seems to be a little bit puzzled too I'm not quiet sure if I was
successful. The first major flaw with my new machine. I aimply copied the data
from Windows Live Mail into the same directory. As I saw all my mails from my
old machine, I was content, may be to early...

> Note that I do use the same color (and
> not ^3) within the pigment statement and this has influence on the final
> appearance even with ambient and diffuse = 0.

Yes, I must admit, I overlooked that. A very valuable hint. I soon implemented
it in my new WIP and yielded better results. It's not about gems but "only"
glass. I try to find a material for old roman glasses by using a similiar
material but filling it with proper scattering and absorbing media. First
results with a glass by Gilles Tran are promising. I will post them here as soon
as possible. At the moment I'm trying to model the geometry of roman glasses in
Wings but observe annoying miscalculations of the normals. I have observed this
not for the first time, in some areas the normals in wings models seems to be
inverted. But that's an other issue. And very annoying baking textures...

Best regards,
Michael


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From: Thomas de Groot
Subject: Re: Another Photon Bug?
Date: 15 Oct 2012 03:00:16
Message: <507bb480$1@news.povray.org>
On 14-10-2012 19:57, MichaelJF wrote:
At the moment I'm trying to model the geometry of roman glasses in
> Wings but observe annoying miscalculations of the normals. I have observed this
> not for the first time, in some areas the normals in wings models seems to be
> inverted. But that's an other issue. And very annoying baking textures...

I have not used Wings for a very long time, but even in Silo, when doing 
complex modelling sometimes faces end up with reversed normals. I 
suppose that you can flip them back, like in Silo. However, I seem to 
remember that Wings had a problem with normal consistency one way or 
another...

Thomas


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From: Jaime Vives Piqueres
Subject: Re: Another Photon Bug?
Date: 15 Oct 2012 07:31:00
Message: <507bf3f4$1@news.povray.org>
On 15/10/12 09:00, Thomas de Groot wrote:
> I seem to remember that Wings had a problem with normal consistency
> one way or another...
>

   I never encountered such problems in my extensive (tough simple) usage
of Wings3D. On my own modeled objects, normals are always fine even if I
do really weird things. I only found such "inverted normals" problem
when importing some OBJ/3DS files from 3rd parties (it never happens if
the imported OBJ/3DS comes from my own objects).

--
Jaime


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From: Thomas de Groot
Subject: Re: Another Photon Bug?
Date: 15 Oct 2012 07:44:11
Message: <507bf70b$1@news.povray.org>
On 15-10-2012 13:30, Jaime Vives Piqueres wrote:
>    I never encountered such problems in my extensive (tough simple) usage
> of Wings3D. On my own modeled objects, normals are always fine even if I
> do really weird things. I only found such "inverted normals" problem
> when importing some OBJ/3DS files from 3rd parties (it never happens if
> the imported OBJ/3DS comes from my own objects).

Must be my dim, degraded memory then, or some past imports I used... :-)

In Silo it can happen sometimes, but because of modelling errors by user ;-)

Thomas


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From: MichaelJF
Subject: Re: Another Photon Bug?
Date: 15 Oct 2012 16:30:00
Message: <web.507c7120682ec917c24cdc420@news.povray.org>
> In Silo it can happen sometimes, but because of modelling errors by user ;-)

May be I did something wrong, but unfortunetaly I have stored only the repaired
version of my old roman decanter. I will have three areas of spiraling bulges
around it and with two of them I encountered this phenomenon which I can only
explain with inverted normals. Usually with wings you can circulize a serious of
similiar edge sequences in one step. With the first two spirals I experienced
that in a certain - and parted - area the circles were inward the object but
with all others outward, which was intended. Unfortunetaly I just tried it with
the third spiral, which I haven't completed so far, and had only outward bounded
circles. That's for the proof by example...
with my orloff diamond I had a similiar experience. Since I will model at least
five different roman glasses (with different materials) the next days I promise
to save and post my next experience with this normal issue within the
newsgroups.

Best regards,
Michael


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