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Howdy,
I'm working on this brass lamp as a logo for my project (LAMP server) home
page, and I'm wondering about a problem when I put the glass globe on the
lamp. BTW: I can't take credit for the flame and I don't remember the user
however in the macro the title "Tea Light" was mentioned. Nice macro ....
dropped right into my scene with no problems.
Back to the problem .... the globe is a lathe object and it's very carefully
placed to avoid coincidence surfaces. The glass is lifted from "simple
glass" in the glass includes. The media containers for the flame show up
when ior is anything > 1 ... set at 1 the glass just doesn't look right,
besides that's not correct anyway (for glass). I've been pretty careful
about making sure textures are radiosity compatible, so I'm fairly sure I've
avoided the "rookie" mistakes, so if anyone has and idea's I'd appreciate
any pointers you'd have to offer.
I'd like to include the globe on the lamp, but it looks pretty decent
without it. The flame looks outstanding! Thanks "Tea Light" artist!!!
Cheers Jim
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Attachments:
Download 'Fossil.png' (240 KB)
Preview of image 'Fossil.png'
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"Jim Holsenback" <jho### [at] hotmail com> wrote:
> Howdy,
>
> I'm working on this brass lamp as a logo for my project (LAMP server) home
> page, and I'm wondering about a problem when I put the glass globe on the
> lamp. BTW: I can't take credit for the flame and I don't remember the user
> however in the macro the title "Tea Light" was mentioned. Nice macro ....
> dropped right into my scene with no problems.
Looks great!
Add a bit of absorbing (black) media to the flame for yet more realism.
> Back to the problem .... the globe is a lathe object and it's very carefully
> placed to avoid coincidence surfaces. The glass is lifted from "simple
> glass" in the glass includes. The media containers for the flame show up
> when ior is anything > 1 ... set at 1 the glass just doesn't look right,
> besides that's not correct anyway (for glass). I've been pretty careful
> about making sure textures are radiosity compatible, so I'm fairly sure I've
> avoided the "rookie" mistakes, so if anyone has and idea's I'd appreciate
> any pointers you'd have to offer.
Can you post a shot of the issue?
I'd expect you to be experienced enough to make sure the flame container doesn't
intersect with the glass globe, so I'm very curious what type of artifact you
have dug up there.
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"clipka" <nomail@nomail> wrote in message
news:web.49cfaf4030aab812ea392f10@news.povray.org...
> Can you post a shot of the issue?
In this image the ior=1.25 ... it shows the artifact clearer, at ior=1.5 the
pattern is repeated multiple times.
The flame macro has three media containers, two near the flame itself
(spheres) and a cylinder going up in y dirirection.
>
> I'd expect you to be experienced enough to make sure the flame container
doesn't
> intersect with the glass globe, so I'm very curious what type of artifact
you
> have dug up there.
yes, that was one of my first stops in my trouble shooting process ... I
have a conditional that allows me to switch from textures to pigments with
no transparency.
the z axis runs through flame adjust and the sphere containers near the
flame are irregular scaled (thin in x dir)
when I run into problems like these I always turn to the documentation for
ideas and played around with maxtracelevel. I had 20 in globals block ...
tried doubling it several times and the problem got worse. decreased it and
I reproduced the black effect that overlapping media containers causes. one
test I didn't do was without radiosity ... I'm not sure if that's worth the
effort adcbailout maybe??? But I'm not sure if that makes sense either. As I
said before the scene seems mechanically sound (not collisions) .... I'm out
of ideas.
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Attachments:
Download 'ior1_25.png' (234 KB)
Preview of image 'ior1_25.png'
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Jim Holsenback nous illumina en ce 2009-03-30 08:52 -->
> "clipka" <nomail@nomail> wrote in message
> news:web.49cfaf4030aab812ea392f10@news.povray.org...
>> Can you post a shot of the issue?
>
> In this image the ior=1.25 ... it shows the artifact clearer, at ior=1.5 the
> pattern is repeated multiple times.
>
> The flame macro has three media containers, two near the flame itself
> (spheres) and a cylinder going up in y dirirection.
>
>> I'd expect you to be experienced enough to make sure the flame container
> doesn't
>> intersect with the glass globe, so I'm very curious what type of artifact
> you
>> have dug up there.
>
> yes, that was one of my first stops in my trouble shooting process ... I
> have a conditional that allows me to switch from textures to pigments with
> no transparency.
>
> the z axis runs through flame adjust and the sphere containers near the
> flame are irregular scaled (thin in x dir)
>
> when I run into problems like these I always turn to the documentation for
> ideas and played around with maxtracelevel. I had 20 in globals block ...
> tried doubling it several times and the problem got worse. decreased it and
> I reproduced the black effect that overlapping media containers causes. one
> test I didn't do was without radiosity ... I'm not sure if that's worth the
> effort adcbailout maybe??? But I'm not sure if that makes sense either. As I
> said before the scene seems mechanically sound (not collisions) .... I'm out
> of ideas.
>
>
>
Does your glass have a thickness, or is it solid trough?
Now, there is a magnifier like effect that should NOT be there. Then, the
flame's container apears to have an ior of 1.000.
--
Alain
-------------------------------------------------
Don't try so hard, the best things come when you least expect them to.
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"Alain" <ele### [at] netscapenet> wrote in message
news:49d0df24$1@news.povray.org...
> Does your glass have a thickness, or is it solid trough?
It's a lathe object, and I rotated it slightly just to make sure I could see
all the way through it. Without a texture it looks like a hollow tube ...
btw: when it's textured hollow on or off appears to make no difference. It
indeed appears to be acting like a solid object.
Just to be clear about it I'm running 3.6.1 on linux ... I'm not on that
machine now but planned on doing some more testing (purely trial and error
at this point) this evening .... perhaps I should post a couple of relevent
code segments to see if anyone can spot what's going on here.
> Now, there is a magnifier like effect that should NOT be there.
yes that describes what we're seeing perfectly .... the effect gets more
pronounced as ior is increased.
> Then, the flame's container apears to have an ior of 1.000.
I don't recall (it's someone elses macro) but I'll check
Thanks
Jim
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Duh - from the looks of it, I'd say your glass globe is *solid*!
Aside from this giving totally unrealistic results anyway, this will result in
the media containers cutting "bubbles" and a chimney into it, which perfectly
explains the effect.
So your objects *do* intersect - not their surfaces, but their volumes.
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Just a quick question: How large is the whole smash, in POV dimensions?
Try scaling everything up by a factor of 10 or even 100. I have the impression
that POV rejects the inner wall of your glass globe (there are hints that there
*is* such an inner wall) due to the glass being too thin.
IIRC the limit is 0.001 units (may be 0.0001, need to look at the code).
Surfaces closer than that will give you trouble.
Post a reply to this message
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"clipka" <nomail@nomail> wrote in message
news:web.49d10dc330aab812f708085d0@news.povray.org...
> Duh - from the looks of it, I'd say your glass globe is *solid*!
well double duh .... that's what appears to be happening but I've proven
that the globe is a tube. I gave it just a pigment and rotated it so I could
see ALL the way throught it!
I even used just a plain cone object with open and hollow keywords and the
effect is still there.
> So your objects *do* intersect - not their surfaces, but their volumes.
doesn't open (if applicable) and hollow keywords overcome that problem?
Cheers
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"clipka" <nomail@nomail> wrote in message
news:web.49d10e9230aab812f708085d0@news.povray.org...
> I have the impression
> that POV rejects the inner wall of your glass globe (there are hints that
there
> *is* such an inner wall) due to the glass being too thin.
then a differenced cone (with some thickness) should overcome that right?
> IIRC the limit is 0.001 units (may be 0.0001, need to look at the code).
> Surfaces closer than that will give you trouble.
if that's true then perhaps that's what I'm battling (infinite thinness)
haha ... that sounds odd!
Exit stage left!
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"Jim Holsenback" <jho### [at] hotmailcom> wrote:
> > So your objects *do* intersect - not their surfaces, but their volumes.
>
> doesn't open (if applicable) and hollow keywords overcome that problem?
Uhm - no.
"Open" basically creates an object with an infinitely thin wall - but such an
object has no interior that an IOR would be applicable to. Or, seen from a
different perspective (and that's also POV's perspective), the interior does
*not* pertain to the wall (which is just an infinitely thin surface), but
rather to whatever is enclosed by it.
But obviously, with some of the surface removed, it is no longer possible to
clearly specify where the inside begins and the outside ends. So combining
"open" (or "clipped_by", for that matter) with an IOR other than 1.0 (or any
other different interior property than the air outside) messes with the object
in a fashion that has no real-world equivalent whatsoever. Unless someone
discovers a material in which the speed of light and the media density depend
on where the light entered the object.
All the while, "hollow" just specifies that the object itself is fit to contain
media. Which, as I just mentioned, doesn't mix well with "open"/"clipped_by"
either.
So what you need is either an "open" shape with a surface that models glass
sufficiently well without relying on IOR (which is difficult), or a CSG
difference of two sor objects defining a finitely thin wall. Or a single lathe
object comprised of a closed spline, or something alike.
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