First: I've not that much experience with radiosity; maybe I'm just
using the wrong parameters...

I wanted to try something simple, when I saw the radiosity pic of
Tony[B]...

I've put a sphere on a checkered plane (hehe, typical POV), made a
blue background and  added a ground fog, to give it some depth.
The light is far away and is an area(9,9)light

Then I added +QR and waited (6hrs)...

There are 2 things, that I see...
I know that the algorithms work this way but it doesn't seem realistic
(How realistic is a single Sphere on a checkered plane?)..

the obvious thing is that the crackles aren't lit by the environment
by radiosity, but only by the sunlight ...

the second thing, (I'm not sure about this) is that there is this edge
on the sphere, that makes it seem, to be a mirror...
In the lower half the sphere is brighter, than the upper half. It's
from the radiosity, reflecting the groundfog-brightness ...
But I didn't expect such a sharp edge ... Maybe I'm wrong ...

except these things it looks quite beautiful .. (I'think)
Because it's short, I've attached the source here ...

Comments and hints are welcome...

--
background{rgb 1}camera{location<1,5,-2>look_at 0}#macro
m(a,b,i)#local d=(b-a)
/8;#local
e=vcross(d,y);#if(i)m(a-e,a+e+2*d,i-1)m(a+e,a+2*d-e,i-1)m(a+3*d-e,a+e
+3*d,i-1)m(a+3*d-e,a+5*d-e,i-1)m(a+6*d-e,a+e+6*d,i-1)m(a+8*d-e,a+e+8*d
,i-1)#else
cylinder{a,b,vlength(d)/3 pigment{rgb 0}}#end#end m(-4*x,2*x,4) // Jan
Walzer

---------source_start--------------
#version unofficial MegaPov 0.7;
global_settings {
        assumed_gamma 1
        radiosity {
                brightness 1
                count 512
                error_bound 0.15
                nearest_count 10
                recursion_limit 3
        }}
background {color rgb <0.0,0.30,0.80>}
fog {   fog_type 2
        distance 1000
        color rgbt <1,1,1,0.1>
        fog_offset 0
        fog_alt 50
        up y
        }

#declare l_size=1000;

#declare GroundTex=texture {
                        pigment {checker color rgb 1, color rgb 0.95}
                        finish {ambient 0 diffuse 0.8}
                        }
light_source {<10000,10000,5000>,
        color rgb <1,0.95,0.5>*1
        area_light
                <0.5,0,-1>*l_size,
                <0,1,0>*l_size,
                9,9 jitter
        }

camera {location <0,10,-30>
        look_at <-5,5,0>
        angle 55
        }

plane { y, 0
        texture {GroundTex}
        }

sphere {y*6,5.5
        texture {GroundTex
                normal {
                        crackle 1
                        scale 0.5
                        }
                }
        }

----------source_end----------------

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Attachments:
Download 'radiosity_test.png' (112 KB)

Preview of image 'radiosity_test.png'

> First: I've not that much experience
> with radiosity; maybe I'm just
> using the wrong parameters...

You're not using the ones I use, at least. No one is quite sure which ones
are the "right" ones. It's mostly a guessing game. I've been using mine
quite happily for some time now. They were developed in conjunction with
Gilles and Xplo et al. Even then they need to be adjusted a bit on a
per-scene basis.

> I wanted to try something simple, when
> I saw the radiosity pic of Tony[B]...

I inspired someone... <rapture> :)

> the obvious thing is that the crackles
> aren't lit by the environment
> by radiosity, but only by the sunlight ...

One thing I wish could be added.

> the second thing, (I'm not sure about this)
> is that there is this edge on the sphere,
> that makes it seem, to be a mirror...

I noticed this when I used count 1 or 2. I don't see why you're getting it
here.

> In the lower half the sphere is brighter, than the upper half. It's
> from the radiosity, reflecting the groundfog-brightness ...
> But I didn't expect such a sharp edge ... Maybe I'm wrong ...

In this unrealistic situation, I think it's correct.

> except these things it looks quite beautiful .. (I'think)

Do radiosity ever look otherwise? :) I'll try your source with my parameters
later. I'm rendering a tabasco bottle for someone.

Post a reply to this message

"news.povray.org" wrote:
> [...]
> the obvious thing is that the crackles aren't lit by the environment
> by radiosity, but only by the sunlight ...
> 

- use 'normal on' in the radiosity block. 
- it's always better to use real surface distortion (isosurface) instead
of normal.  Of course it's much slower.

> the second thing, (I'm not sure about this) is that there is this edge
> on the sphere, that makes it seem, to be a mirror...
> In the lower half the sphere is brighter, than the upper half. It's
> from the radiosity, reflecting the groundfog-brightness ...
> But I didn't expect such a sharp edge ... Maybe I'm wrong ...
> 
> except these things it looks quite beautiful .. (I'think)
> Because it's short, I've attached the source here ...
> 

Some things that should be changed:

- use finish { ambient 0 } for the sphere
- recursion_limit 3 is really unnecessary for such a simple scene.  1 or
maybe 2 is perfectly sufficient.  This also avoids the sharp blue/white
boundary.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

Post a reply to this message

Christoph Hormann <chr### [at] gmxde> wrote:



> "news.povray.org" wrote:
>> [...]
>> the obvious thing is that the crackles aren't lit by the environment
>> by radiosity, but only by the sunlight ...
>> 

> - use 'normal on' in the radiosity block. 

I can't find information on this in the POV manual or the MegaPOV manual
(07)  When was this feature added?

On the other hand, it did help me find the "media on" feature, which might
help in my curren WIP scene (although probably will slow it down immensely)


Geoff

Post a reply to this message

Geoff Wedig wrote:
> 
> I can't find information on this in the POV manual or the MegaPOV manual
> (07)  When was this feature added?
> 
> On the other hand, it did help me find the "media on" feature, which might
> help in my curren WIP scene (although probably will slow it down immensely)
> 

it's mentioned in:

10.2.7. Miscellaneous changes & bug fixes

Never have seen a good example for 'media on' though.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

Post a reply to this message

From: "Christoph Hormann" <chr### [at] gmxde>

>
>
> "news.povray.org" wrote:
> > [...]
> > the obvious thing is that the crackles aren't lit by the
environment
> > by radiosity, but only by the sunlight ...
> >
>
> - use 'normal on' in the radiosity block.
Where is this described ?? I've never read this ...

> - it's always better to use real surface distortion (isosurface)
instead
> of normal.  Of course it's much slower.
It's obvios that this will work, but not necessary to give the thing a
little structure ...

> > the second thing, (I'm not sure about this) is that there is this
edge
> > on the sphere, that makes it seem, to be a mirror...
> > In the lower half the sphere is brighter, than the upper half.
It's
> > from the radiosity, reflecting the groundfog-brightness ...
> > But I didn't expect such a sharp edge ... Maybe I'm wrong ...
> >
> > except these things it looks quite beautiful .. (I'think)
> > Because it's short, I've attached the source here ...
> >
>
> Some things that should be changed:
>
> - use finish { ambient 0 } for the sphere
It already has this from GroundTex ...
That's what I learned first: In Radiosity pics objects don't need
Ambient, or they will glow...

> - recursion_limit 3 is really unnecessary for such a simple scene.
1 or
> maybe 2 is perfectly sufficient.  This also avoids the sharp
blue/white
> boundary.
I'd preferred to go even deeper ...

--
background{rgb 1}camera{location<1,5,-2>look_at 0}#macro
m(a,b,i)#local d=(b-a)
/8;#local
e=vcross(d,y);#if(i)m(a-e,a+e+2*d,i-1)m(a+e,a+2*d-e,i-1)m(a+3*d-e,a+e
+3*d,i-1)m(a+3*d-e,a+5*d-e,i-1)m(a+6*d-e,a+e+6*d,i-1)m(a+8*d-e,a+e+8*d
,i-1)#else
cylinder{a,b,vlength(d)/3 pigment{rgb 0}}#end#end m(-4*x,2*x,4) // Jan
Walzer

Post a reply to this message

"Tony[B]" <ben### [at] catholicorg>
> > First: I've not that much experience
> > with radiosity; maybe I'm just
> > using the wrong parameters...
>
> You're not using the ones I use, at least. No one is quite sure
which ones
> are the "right" ones. It's mostly a guessing game. I've been using
mine
> quite happily for some time now. They were developed in conjunction
with
> Gilles and Xplo et al. Even then they need to be adjusted a bit on a
> per-scene basis.
I used the guide in the radiosity chapter of the old docs ...
Of course, I know, Nathan has changed(rewritten?) the radiosity part,
but I hoped, the params still have the same function...

> > I wanted to try something simple, when
> > I saw the radiosity pic of Tony[B]...
>
> I inspired someone... <rapture> :)
No ... not inspired ;)...
I just felt I also need some testing in Radiosity, cause everyone else
is doing this ...

> > the obvious thing is that the crackles
> > aren't lit by the environment
> > by radiosity, but only by the sunlight ...
>
> One thing I wish could be added.
Christoph told me something about the "normal on" parameter in the
radio-statement...
I'm rendering now ...

> > the second thing, (I'm not sure about this)
> > is that there is this edge on the sphere,
> > that makes it seem, to be a mirror...
> I noticed this when I used count 1 or 2. I don't see why you're
getting it
> here.

> > In the lower half the sphere is brighter, than the upper half.
It's
> > from the radiosity, reflecting the groundfog-brightness ...
> > But I didn't expect such a sharp edge ... Maybe I'm wrong ...
>
> In this unrealistic situation, I think it's correct.
>
> > except these things it looks quite beautiful .. (I'think)
> Do radiosity ever look otherwise? :) I'll try your source with my
parameters
Of course not ...
> later. I'm rendering a tabasco bottle for someone.
I hope it will be bigger than the last Image ... ;)


--
background{rgb 1}camera{location<1,5,-2>look_at 0}#macro
m(a,b,i)#local d=(b-a)
/8;#local
e=vcross(d,y);#if(i)m(a-e,a+e+2*d,i-1)m(a+e,a+2*d-e,i-1)m(a+3*d-e,a+e
+3*d,i-1)m(a+3*d-e,a+5*d-e,i-1)m(a+6*d-e,a+e+6*d,i-1)m(a+8*d-e,a+e+8*d
,i-1)#else
cylinder{a,b,vlength(d)/3 pigment{rgb 0}}#end#end m(-4*x,2*x,4) // Jan
Walzer

Post a reply to this message

Christoph Hormann <chr### [at] gmxde> wrote:



> Geoff Wedig wrote:
>> 
>> I can't find information on this in the POV manual or the MegaPOV manual
>> (07)  When was this feature added?
>> 
>> On the other hand, it did help me find the "media on" feature, which might
>> help in my curren WIP scene (although probably will slow it down immensely)
>> 

> it's mentioned in:

> 10.2.7. Miscellaneous changes & bug fixes

Don't know how I missed it, since I read pretty carefully.  Must be going
blind or stupid, and last I checked, my eyes were fine... *sigh*

> Never have seen a good example for 'media on' though.

Well, I'll do a test render, and if it works, great.  If it doesn't I kill
it.

Geoff

Post a reply to this message

I think a sphere on a plane always ends up with a sharp line because of the
underlying geometry.  Your sphere has a brighter than average division line
because of the cumulative effect of all that fog (looking at your horizon I
can see a whiter-than-white stripe that gets reflected in your sphere).

I know nothing about radiosity and look forward to seeing your experiment
evolve.

BTW, unless you are the news administrator it would be nice if you changed
your name to something other than "news.povray.org".

Post a reply to this message

"news.povray.org" wrote:
> 
> >
> > - use finish { ambient 0 } for the sphere
> It already has this from GroundTex ...

Oops, i missed that, sorry.

Christoph

-- 
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other 
things on: http://www.schunter.etc.tu-bs.de/~chris/

Post a reply to this message