Hi,

I was wondering how I can make an object generate light for a radiosity
scene? Reference to the documentation are welcome. I am somewhat confused
if this is done differently for radiosity than what is mentioned in the
documentation I have seen so far.

Thank you for any suggestions.

Post a reply to this message

incognito wrote:
> Hi,
> 
> I was wondering how I can make an object generate light for a radiosity
> scene? Reference to the documentation are welcome. I am somewhat confused
> if this is done differently for radiosity than what is mentioned in the
> documentation I have seen so far.

I don't see anything wrong in the docs about this issue.  You can 
increase the emission of radiance of a surface by increasing the ambient 
finish component.  It is also mentioned as an example in the radiosity 
tutorial:

http://www.povray.org/documentation/view/106/

(note the online version misses the image texts)

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 25 Oct. 2003 _____./\/^>_*_<^\/\.______

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Christoph Hormann wrote:
>incognito wrote:
>> Hi,
>>
>> I was wondering how I can make an object generate light for a radiosity
>> scene? Reference to the documentation are welcome. I am somewhat confused
>> if this is done differently for radiosity than what is mentioned in the
>> documentation I have seen so far.
>
>I don't see anything wrong in the docs about this issue.  You can
>increase the emission of radiance of a surface by increasing the ambient
>finish component.  It is also mentioned as an example in the radiosity
>tutorial:
>
>http://www.povray.org/documentation/view/106/
>
>(note the online version misses the image texts)
>
>Christoph

Thanks for your reply.

Don't get me wrong - I have no problems w/the documentation.

Just confused cause I need to do both radiosity and ray tracing for this
first POV-ray assignment I've ever had and am learning a lot of info in a
short amt of time.

Thanks.
>
>POV-Ray tutorials, include files, Sim-POV,
>HCR-Edit and more: http://www.tu-bs.de/~y0013390/
>Last updated 25 Oct. 2003 _____./\/^>_*_<^\/\.______
>

Post a reply to this message

incognito wrote:
>Christoph Hormann wrote:
>>incognito wrote:
>>> Hi,
>>>
>>> I was wondering how I can make an object generate light for a radiosity
>>> scene? Reference to the documentation are welcome. I am somewhat confused
>>> if this is done differently for radiosity than what is mentioned in the
>>> documentation I have seen so far.
>>
>>I don't see anything wrong in the docs about this issue.  You can
>>increase the emission of radiance of a surface by increasing the ambient
>>finish component.  It is also mentioned as an example in the radiosity
>>tutorial:
>>
>>http://www.povray.org/documentation/view/106/
>>
>>(note the online version misses the image texts)
>>
>>Christoph
>
>Thanks for your reply.
>
>Don't get me wrong - I have no problems w/the documentation.
>
>Just confused cause I need to do both radiosity and ray tracing for this
>first POV-ray assignment I've ever had and am learning a lot of info in a
>short amt of time.
>
>Thanks.
>>
>>POV-Ray tutorials, include files, Sim-POV,
>>HCR-Edit and more: http://www.tu-bs.de/~y0013390/
>>Last updated 25 Oct. 2003 _____./\/^>_*_<^\/\.______
>>
>

Hi again all,

Now that I have partially created my light source in my radiosity trace by
setting its ambient light level to 0.7 and setting the diffuse light value
of all the other objects in the scene to be 0.5, I am confused I should
make that light source object Luminous or Shiny? Really need the answer
quick (if possible).

Thank you very much.

Post a reply to this message

"incognito" <nomail@nomail> wrote in message
news:web.3fc5dad2b2b1540ca688d5670@news.povray.org...

>
> Hi again all,
>
> Now that I have partially created my light source in my radiosity trace by
> setting its ambient light level to 0.7 and setting the diffuse light value
> of all the other objects in the scene to be 0.5, I am confused I should
> make that light source object Luminous or Shiny? Really need the answer
> quick (if possible).
>
> Thank you very much.
>

I'm not sure what you mean by luminous or shiny in this context. 'Luminous'
would seem to equate to ambient value, but you've already stated that that is
set to 0.7. 'Shiny' presumably means the reflection value, but that is not
relevant in this case.

BTW could you just assure us that you've read the advanced tutorial on radiosity
scenes (4.1 in the docs). I just want to check you're doing what you actually
want, rather than misunderstanding something (radiosity works with scenes that
contain conventional light-sources as well as those lit entirely by 'glowing'
objects).

Here is a simple radiosity scene with no conventional lights:

#version 3.5;

#declare Radiosity=on;
#include "colors.inc"

global_settings {
  assumed_gamma 1.0
  #if (Radiosity)
    radiosity {
      pretrace_start 0.08
      pretrace_end   0.02
      count 35

      nearest_count 10
      error_bound 1
      recursion_limit 3

      low_error_factor 0.1
      gray_threshold 0.25
      minimum_reuse 0.02
      brightness 10

      always_sample off

      adc_bailout 0.01
    }
  #end
}

// ----------------------------------------

camera {
  location  <0,2,-4>
  look_at   <0,0,0>
}

// 'lightbulb'
sphere{
  0,0.5
  pigment{Yellow}
  finish{ambient 1}
  translate x*1
}

// 'lit object'
sphere{
  0.0.5
  pigment{White}
  finish{ambient 0}
  translate x*-1
}

box{ // also lit
  -10,10
  hollow
  pigment{White}
  finish{ambient 0}
}

Post a reply to this message

Tom Melly wrote:
>"incognito" <nomail[at]nomail> wrote in message
>news:web.3fc5dad2b2b1540ca688d5670[at]news.povray.org...
>
>>
>> Hi again all,
>>
>> Now that I have partially created my light source in my radiosity trace by
>> setting its ambient light level to 0.7 and setting the diffuse light value
>> of all the other objects in the scene to be 0.5, I am confused I should
>> make that light source object Luminous or Shiny? Really need the answer
>> quick (if possible).
>>
>> Thank you very much.
>>
>
>I'm not sure what you mean by luminous or shiny in this context. 'Luminous'
>would seem to equate to ambient value, but you've already stated that that is
>set to 0.7. 'Shiny' presumably means the reflection value, but that is not
>relevant in this case.

Yes, realized this soon after I posted
>
>BTW could you just assure us that you've read the advanced tutorial on radiosity
>scenes (4.1 in the docs). I just want to check you're doing what you actually
>want, rather than misunderstanding something (radiosity works with scenes that
>contain conventional light-sources as well as those lit entirely by 'glowing'
>objects).

The interesting thing is I asked the prof if he wanted us to have pure
radiosity or radiosity with conventional light sources a week ago and he
replied he wanted pure radiosity with one object generating light (a sun)
and also a light source that would act as the sky...so that is what I have
been trying to do. So far, I believe I have the sky ok but not sure if the
object light is working correctly (i.e. doesn't seem like the objects
nearer to the sun object are lit up any more than those further away (which
I take to be how it *should* work).

From what you are saying below, sounds like I do not need to set the diffuse
vals of the other objects (just ambient to 0 and translate x), am I
understanding that correctly?

Thanks.

>
>Here is a simple radiosity scene with no conventional lights:
>
>#version 3.5;
>
>#declare Radiosity=on;
>#include "colors.inc"
>
>global_settings {
>  assumed_gamma 1.0
>  #if (Radiosity)
>    radiosity {
>      pretrace_start 0.08
>      pretrace_end   0.02
>      count 35
>
>      nearest_count 10
>      error_bound 1
>      recursion_limit 3
>
>      low_error_factor 0.1
>      gray_threshold 0.25
>      minimum_reuse 0.02
>      brightness 10
>
>      always_sample off
>
>      adc_bailout 0.01
>    }
>  #end
>}
>
>// ----------------------------------------
>
>camera {
>  location  <0,2,-4>
>  look_at   <0,0,0>
>}
>
>// 'lightbulb'
>sphere{
>  0,0.5
>  pigment{Yellow}
>  finish{ambient 1}
>  translate x*1
>}
>
>// 'lit object'
>sphere{
>  0.0.5
>  pigment{White}
>  finish{ambient 0}
>  translate x*-1
>}
>
>box{ // also lit
>  -10,10
>  hollow
>  pigment{White}
>  finish{ambient 0}
>}
>

Post a reply to this message

In article <web.3fc64abeb2b1540c240f43310@news.povray.org>,
 "incognito" <nomail@nomail> wrote:

> The interesting thing is I asked the prof if he wanted us to have pure
> radiosity or radiosity with conventional light sources a week ago and he
> replied he wanted pure radiosity with one object generating light (a sun)
> and also a light source that would act as the sky...so that is what I have
> been trying to do.

You sure he said to do that? The usual arrangement has things the other 
way around. Light sources, even area lights, are very bad at doing 
diffuse light coming from large areas, such as a sky. Radiosity is very 
bad at doing light coming from more or less a single point. Radiosity 
for the sky and an area light for the sun would make much more sense. 
And if he said to use a light source, it wasn't pure radiosity.


> So far, I believe I have the sky ok but not sure if the
> object light is working correctly (i.e. doesn't seem like the objects
> nearer to the sun object are lit up any more than those further away (which
> I take to be how it *should* work).

Try removing all light sources...your radiosity lighting may simply be 
too dim.


> From what you are saying below, sounds like I do not need to set the diffuse
> vals of the other objects (just ambient to 0 and translate x), am I
> understanding that correctly?

You only need to adjust the diffuse value if the default of 0.6 doesn't 
suit your needs. I generally set the default ambient to 0 and the 
default diffuse to 1 (and put a dim, shadowless light at the camera 
position to fill in shadows).

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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On Thu, 27 Nov 2003 17:07:28 -0000, "Tom Melly" <tom### [at] tomandlucouk> wrote:
> > I am confused I should make that light source object Luminous or Shiny?
>
> I'm not sure what you mean by luminous or shiny in this context.

I suppose those could be predefined values from POV/include/finish.inc

  #declare Shiny = finish {specular 1 roughness 0.001}
  #declare Luminous = finish {ambient 1  diffuse 0}

ABX

Post a reply to this message

Christopher James Huff wrote:
>In article <web.3fc64abeb2b1540c240f43310[at]news.povray.org>,
> "incognito" <nomail[at]nomail> wrote:
>
>> The interesting thing is I asked the prof if he wanted us to have pure
>> radiosity or radiosity with conventional light sources a week ago and he
>> replied he wanted pure radiosity with one object generating light (a sun)
>> and also a light source that would act as the sky...so that is what I have
>> been trying to do.
>
>You sure he said to do that? The usual arrangement has things the other
>way around. Light sources, even area lights, are very bad at doing
>diffuse light coming from large areas, such as a sky. Radiosity is very
>bad at doing light coming from more or less a single point. Radiosity
>for the sky and an area light for the sun would make much more sense.
>And if he said to use a light source, it wasn't pure radiosity.
>
If it clarifies any, here is the assignment:

http://www.evl.uic.edu/aej/488/fall2k3.hw4.html

>
>> So far, I believe I have the sky ok but not sure if the
>> object light is working correctly (i.e. doesn't seem like the objects
>> nearer to the sun object are lit up any more than those further away (which
>> I take to be how it *should* work).
>
>Try removing all light sources...your radiosity lighting may simply be
>too dim.
>

I just did this and it was not too dim. I think it does seem to be acting as
a light source now just maybe not very noticeable because I do have a
relatively light background. (My background ambient is set to only 0.4 and
the sun is set to ambient 1). I will go ahead and try the diffuse at a
higher value too since I would like it to be more noticeable.

Thanks.
>
>> From what you are saying below, sounds like I do not need to set the diffuse
>> vals of the other objects (just ambient to 0 and translate x), am I
>> understanding that correctly?
>
>You only need to adjust the diffuse value if the default of 0.6 doesn't
>suit your needs. I generally set the default ambient to 0 and the
>default diffuse to 1 (and put a dim, shadowless light at the camera
>position to fill in shadows).
>
>Christopher James Huff <cja### [at] earthlinknet>
>http://home.earthlink.net/~cjameshuff/
>POV-Ray TAG: chr### [at] tagpovrayorg
>http://tag.povray.org/
>

Post a reply to this message

In article <web.3fc69a25b2b1540cca01221d0@news.povray.org>,
 "incognito" <nomail@nomail> wrote:

> >You sure he said to do that? The usual arrangement has things the other
> >way around. Light sources, even area lights, are very bad at doing
> >diffuse light coming from large areas, such as a sky. Radiosity is very
> >bad at doing light coming from more or less a single point. Radiosity
> >for the sky and an area light for the sun would make much more sense.
> >And if he said to use a light source, it wasn't pure radiosity.
> >
> If it clarifies any, here is the assignment:
> 
> http://www.evl.uic.edu/aej/488/fall2k3.hw4.html

Hmm...some apparent misconceptions. Radiosity is a lighting algorithm, 
not a rendering algorithm, and POV-Ray *always* raytraces. With POV, you 
can raytrace a scene with conventional lighting or monte-carlo radiosity 
(which itself uses raytracing to take the radiosity samples), but you 
usually use radiosity to complement ordinary lighting.

An orrery is a poor structure to use for demonstrating radiosity. The 
planets will not reflect a visible amount of light on each other, will 
only have a slight influence on their moons, and it is a very 
inefficient way to simulate the sun. Radiosity will only benefit the 
rest of the scene, which is apparently secondary to the project. A 
typical example of a radiosity scene would be an outdoor structure with 
lots of shadows or a room with sunlight pouring in through a window.


> I just did this and it was not too dim. I think it does seem to be acting as
> a light source now just maybe not very noticeable because I do have a
> relatively light background. (My background ambient is set to only 0.4 and
> the sun is set to ambient 1). I will go ahead and try the diffuse at a
> higher value too since I would like it to be more noticeable.

Ah...increasing diffuse will just make the scene brighter, it won't make 
the sun contribute more. You don't get much light from the sun becase it 
isn't much brighter than the sky...it is only a little more than twice 
as bright. The light from your sun does fall off with distance, which 
makes it insignificant compared to the light from the sky. Use a much 
higher ambient value for the sun, and it will shine brighter. Dimming 
the sky will make the effect more pronounced.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/

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