OK ...
I tried "normals on" and its so beatiful now ...
It took 'bout 2 hours with a crash between ...
So maybe the lower half is not correct with radio....
I can't see any artifacts, but I can't give my word ..


--
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

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Attachments:
Download 'radiosity_test.png' (121 KB)

Preview of image 'radiosity_test.png'

Here's my version, with my rad settings, a sky_sphere and a corrected sphere
texture.

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Attachments:
Download 'janzrad.jpg' (18 KB)

Preview of image 'janzrad.jpg'

Tony[B] <ben### [at] catholicorg> wrote:

> Here's my version, with my rad settings, a sky_sphere and a corrected sphere
> texture.

Why is it so yellow on the bottom?  I don't see anything that'd give it that
color.

Geoff

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Your settings are ?

... did you change the finish of the texture, or only the Rad-Settings
?

seems quite dark for me ... but so far .. thanx ..

--
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

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Hehe ... I asked this myself ...
The Heaven is blue ...
so the most ambient is blue ...
The sun is yellow ...
so where the sun hits the sphere, there is the ambient and the sun
(blue + yellow) that gives white ...

The shadow of the sphere, that is not lit by the sun is blue, because
of the ambient ...
below the sphere there is no ambient, but the sun brightens some parts
...
so it gets yellow ...

You understand ?

--
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

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Jan Walzer wrote:
> 
> Hehe ... I asked this myself ...
> The Heaven is blue ...
> so the most ambient is blue ...
> The sun is yellow ...
> so where the sun hits the sphere, there is the ambient and the sun
> (blue + yellow) that gives white ...
> 
> The shadow of the sphere, that is not lit by the sun is blue, because
> of the ambient ...
> below the sphere there is no ambient, but the sun brightens some parts
> ...
> so it gets yellow ...
> 
> You understand ?
> 

Because the sphere and floor themselves are white,  the yellow light
leades to yellow color where the sky's effect is not that strong.  

Christoph

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

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> Your settings are ?

global_settings
{
 assumed_gamma 1
 ini_option "+QR"
 radiosity
 {
  pretrace_start 0.32 pretrace_end 0.08
  count 300 nearest_count 4
  error_bound 0.01 recursion_limit 1
  low_error_factor 0.5 gray_threshold 0
  minimum_reuse 0 brightness 1
  max_sample 1 adc_bailout 0.01/2 normal on
 }
}

> ... did you change the finish of the
> texture, or only the Rad-Settings ?

I only changed the rad-settings and the pigment of the sphere.

> seems quite dark for me ... but so far .. thanx ..

That can be fixed by using a higher brightness or gray_threshold. I didn't
mean to imitate your settings, just show you that I had fixed "reflection"
the problem.

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Jan Walzer wrote:
> 
> Hehe ... I asked this myself ...
> The Heaven is blue ...
> so the most ambient is blue ...
> The sun is yellow ...
> so where the sun hits the sphere, there is the ambient and the sun
> (blue + yellow) that gives white ...
> 
> The shadow of the sphere, that is not lit by the sun is blue, because
> of the ambient ...
> below the sphere there is no ambient, but the sun brightens some parts
> ...
> so it gets yellow ...
> 
> You understand ?

No, I don't. I have never seen any situation in real life that this
would represent. I think radiosity does a poor job of realistic
ligthing representations and is over rated. I further think those who
use it just imagine that it gives a good lighting model when in reality
it fails the reality test. Further more...

Well that's what I think anyway :)

-- 
Ken Tyler

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Ken wrote:
> 
> No, I don't. I have never seen any situation in real life that this
> would represent.

How can you compare then? 

I have seen several photometric images of physical setups and
corresponding rad simulations in IEEE and other publications
which clearly show the validity of radiosity. There are differences
in implementations, like noise in the ray based radiosity, but the
basic concept is solid.

The problem with all radiosity implementations is that there are too
many cryptic parameters to tweak so users in general use non optimal
setup which ruins the simulation. There is an EU project ARCADE which
tries to automate the parameter tweak phase among other things so that
you don't have to be "Certified Radiosity Technician" to produce good
results. http://www-imagis.imag.fr/ARCADE/

This particular scene is a poor choice for meaasuring how realistic
the simulation is for two reasons. The "sky" emits the same amount of
"energy" as the "sun". Nobody has ever seen this situation so it's a
bit difficult to compare. The scene is also uniform in all directions.


There is something funny going on with background{} and radiosity.
I rendered the same scene enclosed in a sphere and the anomaly at
the bottom of the sphere disappeared.
http://hammer.prohosting.com/~kkivisal/sphere.jpg


______________________________________________________________________
Kari Kivisalo                                  http://www.kivisalo.net

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Kari Kivisalo wrote:
> 
> Ken wrote:
> >
> > No, I don't. I have never seen any situation in real life that this
> > would represent.
> 
> How can you compare then?

Simple. In front of me I place a solid red ball on a white piece of paper
with a fairly bright light shining on it. I see a fairly dark shadow but
absolutely zero evedence of red color bleed. I now repeat the experiment
with other colored objects. Again no color bleed.

Are we trying to mimic real life or photometric experiments ?

I remain unconvinced.

-- 
Ken Tyler

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