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Am 08.11.2012 04:08, schrieb taftj:
> Thank you- that did work, but apparently I'm still not understanding something
> because when I remove the light source I see blackness. I thought the point of
> radiosity was that there was some "general" light without needing a specific
> light source.
No, the main point of radiosity is that shadows are illuminated by
diffuse light from other objects.
A side effect of radiosity is that you /can/ also get illumination from
a sky sphere or background (this is automatic), and even objects (this
requires a suitable finish setting; previously this could be done by
using a non-zero "ambient" finish term, but this was originally just a
hack and has always been troublesome, so as of POV-Ray 3.7 the new
"emission" term needs to be used instead).
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On 11/6/2012 3:14 AM, Thomas de Groot wrote:
> On 6-11-2012 6:58, taftj wrote:
>> Could somebody kindly post complete code for a very simple scene that
>> uses
>> radiosity? Maybe a white plane with a white box and nothing else. No
>> matter
>> what I try, I get either blackness or no effect. Something's not
>> clicking I
>> guess :(
>>
>> Thank you!
>>
>>
>
> Take one of the basic scenes from the Insert Menu, and add the following
> block (using version 3.7 btw):
>
> global_settings {
> adc_bailout 0.003922
> assumed_gamma 1.0
> max_trace_level 10
> number_of_waves 10
> noise_generator 2
> radiosity {
> brightness 1.0
> count 100, 500
> error_bound 1.8
> gray_threshold 0.0
> low_error_factor 0.5
> minimum_reuse 0.015
> nearest_count 10, 5
> recursion_limit 2
> adc_bailout 0.01
> media off
> normal off
> always_sample off
> pretrace_start 0.08
> pretrace_end 0.004
> }
> }
>
> Thomas
>
>
Hi Thomas,
I know this is kind of an old message, but I'm hoping you are still out
there...
I tried your suggestion with several of the canned examples from the
insert menu and have found an unexpected (by me) result.
On scenes such as Basic_Scene_05: Grass with small clouds in sky, your
settings cause the sky to go from a bright sunny blue sky in the
original scene, to a dark, grey, stormy-looking sky.
I was wondering if you, or anyone else, could explain what is going on.
I'm using POVray 3.7 RC7.
Todd
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On 19-6-2013 16:48, Todd Carnes wrote:
> Hi Thomas,
>
> I know this is kind of an old message, but I'm hoping you are still out
> there...
>
> I tried your suggestion with several of the canned examples from the
> insert menu and have found an unexpected (by me) result.
>
> On scenes such as Basic_Scene_05: Grass with small clouds in sky, your
> settings cause the sky to go from a bright sunny blue sky in the
> original scene, to a dark, grey, stormy-looking sky.
>
> I was wondering if you, or anyone else, could explain what is going on.
>
> I'm using POVray 3.7 RC7.
Elementary, my dear Watson ;-)
The basic scene comes from an older version of POV. In version 3.7, the
ambient parameter in finish does not work as before. You have to replace
it by emission and the scene renders correctly.
Thomas
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On 6/19/2013 10:59 AM, Thomas de Groot wrote:
> Elementary, my dear Watson ;-)
>
> The basic scene comes from an older version of POV. In version 3.7, the
> ambient parameter in finish does not work as before. You have to replace
> it by emission and the scene renders correctly.
>
> Thomas
Thank you for the prompt answer. :)
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Musing...
It is not a /bug/ strictly speaking, as the scene renders correctly in
its original state, without the radiosity block. The reason is
adequately described in the wiki Docs (section 1.3.5.3.2).
However, it is something to remain aware of when building scenes from
pre-defined ones.
Thomas
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On 11/8/2012 8:20 AM, clipka wrote:
> A side effect of radiosity is that you /can/ also get illumination from
> a sky sphere or background (this is automatic), and even objects (this
> requires a suitable finish setting; previously this could be done by
> using a non-zero "ambient" finish term, but this was originally just a
> hack and has always been troublesome, so as of POV-Ray 3.7 the new
> "emission" term needs to be used instead).
I'm sure that "under-the-hood" emission probably works differently from
ambient, but from where I'm standing it looks like all they did was
trade one word for another.
Todd
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> On 11/8/2012 8:20 AM, clipka wrote:
>> A side effect of radiosity is that you /can/ also get illumination from
>> a sky sphere or background (this is automatic), and even objects (this
>> requires a suitable finish setting; previously this could be done by
>> using a non-zero "ambient" finish term, but this was originally just a
>> hack and has always been troublesome, so as of POV-Ray 3.7 the new
>> "emission" term needs to be used instead).
>
> I'm sure that "under-the-hood" emission probably works differently from
> ambient, but from where I'm standing it looks like all they did was
> trade one word for another.
>
> Todd
>
They look the same, but there is a big difference:
When radiosity is turned on, all ambient to turned off.
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Am 20.06.2013 09:06, schrieb Thomas de Groot:
> Musing...
>
> It is not a /bug/ strictly speaking, as the scene renders correctly in
> its original state, without the radiosity block. The reason is
> adequately described in the wiki Docs (section 1.3.5.3.2).
>
> However, it is something to remain aware of when building scenes from
> pre-defined ones.
Actually, the most important thing to remain aware of when dealing with
older scenes is to make sure that the scene begins with a
#version ...
statement. Normally this should make everything else fall into place
automatically.
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Am 23.06.2013 18:00, schrieb Todd Carnes:
> On 11/8/2012 8:20 AM, clipka wrote:
>> A side effect of radiosity is that you /can/ also get illumination from
>> a sky sphere or background (this is automatic), and even objects (this
>> requires a suitable finish setting; previously this could be done by
>> using a non-zero "ambient" finish term, but this was originally just a
>> hack and has always been troublesome, so as of POV-Ray 3.7 the new
>> "emission" term needs to be used instead).
>
> I'm sure that "under-the-hood" emission probably works differently from
> ambient, but from where I'm standing it looks like all they did was
> trade one word for another.
"They" was me, and there is a fundamental reason why the change was made.
The original intention of the "ambient" term was to provide a means to
(very roughly) approximate what the radiosity feature is doing at much
more computational costs: The light that an object is receiving
indirectly from other objects (IOW ambient illumination, hence the name
of the parameter) and reflecting back diffusely.
(Here's already an initial flaw that has /not/ been tackled yet: How
much ambient light an object reflects in this way obviously does not
only depend on the material properties, but also on how much ambient
light the object is receiving in the first place, which in turn depends
on the geometry of the scene; making the ambient term a part of the
material settings is therefore a questionable decision, and some future
revsion of the SDL - say, some POV-Ray 4.0 SDL - should correct it.)
Users of course found out that this "ambient" term also provided a means
to let objects appear to be glowing - which became even more exciting
when the radiosity feature was added.
Unfortunately, this dual use of the "ambient" term led to a conflicting
situation: While a non-radiosity scene would need all materials to have
a non-zero "ambient" term (and a non-zero ambient_light setting) to look
reasonably ok, a radiosity scene would need all non-glowing materials to
have a zero "ambient" term (or to have ambient_light be zero, but this
would prevent the simulation of glowing objects entirely). So you'd
essentially need two versions of each material: One for non-radiosity
scenes, and one for radiosity scenes.
The introduction of the "emission" setting solves this conflict, by
providing different knobs for each of the purposes "ambient" had come to
be used for: The "ambient" setting can now be used without limitations
to simulate the effect of indirect light in non-radiosity scenes,
without undesired side effects in radiosity scenes (as it is turned off
entirely there, being replaced by the radiosity mechanism); at the same
time, glowing materials can now be modeled without limitations using the
"emission" setting instead, as it is available in both radiosity and
non-radiosity scenes.
(As a side note, another - albeit less important - difference is that
the "emission" setting is insensitive to the ambient_light parameter.)
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On 7/16/2013 4:25 PM, clipka wrote:
> Am 23.06.2013 18:00, schrieb Todd Carnes:
>> On 11/8/2012 8:20 AM, clipka wrote:
>>> A side effect of radiosity is that you /can/ also get illumination from
>>> a sky sphere or background (this is automatic), and even objects (this
>>> requires a suitable finish setting; previously this could be done by
>>> using a non-zero "ambient" finish term, but this was originally just a
>>> hack and has always been troublesome, so as of POV-Ray 3.7 the new
>>> "emission" term needs to be used instead).
>>
>> I'm sure that "under-the-hood" emission probably works differently from
>> ambient, but from where I'm standing it looks like all they did was
>> trade one word for another.
>
> "They" was me, and there is a fundamental reason why the change was made.
>
> The original intention of the "ambient" term was to provide a means to
> (very roughly) approximate what the radiosity feature is doing at much
> more computational costs: The light that an object is receiving
> indirectly from other objects (IOW ambient illumination, hence the name
> of the parameter) and reflecting back diffusely.
>
> (Here's already an initial flaw that has /not/ been tackled yet: How
> much ambient light an object reflects in this way obviously does not
> only depend on the material properties, but also on how much ambient
> light the object is receiving in the first place, which in turn depends
> on the geometry of the scene; making the ambient term a part of the
> material settings is therefore a questionable decision, and some future
> revsion of the SDL - say, some POV-Ray 4.0 SDL - should correct it.)
>
> Users of course found out that this "ambient" term also provided a means
> to let objects appear to be glowing - which became even more exciting
> when the radiosity feature was added.
>
> Unfortunately, this dual use of the "ambient" term led to a conflicting
> situation: While a non-radiosity scene would need all materials to have
> a non-zero "ambient" term (and a non-zero ambient_light setting) to look
> reasonably ok, a radiosity scene would need all non-glowing materials to
> have a zero "ambient" term (or to have ambient_light be zero, but this
> would prevent the simulation of glowing objects entirely). So you'd
> essentially need two versions of each material: One for non-radiosity
> scenes, and one for radiosity scenes.
>
> The introduction of the "emission" setting solves this conflict, by
> providing different knobs for each of the purposes "ambient" had come to
> be used for: The "ambient" setting can now be used without limitations
> to simulate the effect of indirect light in non-radiosity scenes,
> without undesired side effects in radiosity scenes (as it is turned off
> entirely there, being replaced by the radiosity mechanism); at the same
> time, glowing materials can now be modeled without limitations using the
> "emission" setting instead, as it is available in both radiosity and
> non-radiosity scenes.
>
> (As a side note, another - albeit less important - difference is that
> the "emission" setting is insensitive to the ambient_light parameter.)
>
Thank you for the very detailed explanation. I've learned a lot from it. :)
Todd
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