Jan Dvorak nous apporta ses lumieres en ce 2007/11/13 10:09:
> Alain napsal(a):
>> Jan Dvorak nous apporta ses lumieres en ce 2007/11/13 00:25:
>>> Alain napsal(a):
>>>> Jan Dvorak nous apporta ses lumieres en ce 2007/11/11 05:48:
>>>>> Hello,
>>>>>  When I use double_illuminate in a radiosity scene it does nothing 
>>>>> (it does get double_illuminated by light_sources).
>>>>> Here's a scene to illustrate:
>>>>>
>>>>> default{finish{ambient 0}}
>>>>> camera{location <3,4,5> look_at 0}
>>>>> polygon{5,x,y,-x,-y,x pigment{rgb 1}double_illuminate translate  z}
>>>>> polygon{5,x,y,-x,-y,x pigment{rgb 1}double_illuminate translate -z}
>>>>> background{rgb z}
>>>>> global_settings{radiosity{}}
>>>>> sphere{-y/2,0.5 texture{pigment{rgb y}finish{ambient 10 diffuse 0}}}
>>>>> light_source{y/2,rgb x}
>>>>>
>>>>> Is it a bug or it is intentional?
>>>> Working as expected.
>>>> The polygons are double_illuminate be the light_source (red), whitch 
>>>> contribute on both faces.
>>>> They are lighted in blue from the background, giving that magenta tint.
>>>> The faces near the high ambient grees sphere are illuminated in 
>>>> green. They are also affected by the other polygon, lighted in red, 
>>>> and, weekly, the blue background.
>>>>
>>>
>>> As for MegaPOV 1.2.1 @ WinXP the front square doesn't get doubly 
>>> illuminated by the green sphere. Can you post your configuration, 
>>> please?
>> It's not double_illuminated by radiosity, and sould'nt be.
>>
> How come it shouldn't?
Radiosity ignore double_illuminate, it never use samples comming from behind the 
surface.
You can fake it as follow:
default{finish{ambient 0}}
camera{location <3,4,5> look_at 0}
polygon{5,x,y,-x,-y,x pigment{rgb 1}double_illuminate translate  z no_shadow}
polygon{5,x,y,-x,-y,x pigment{rgb 1}double_illuminate translate -z no_shadow}
background{rgb z}
global_settings{radiosity{count 1000 error_bound 0.9}}
sphere{-y/2,0.5 texture{pigment{rgb y}finish{ambient 10 diffuse 0}}}
light_source{y/2,rgb x}
#declare Offset = 1.05;
polygon{5,x,y,-x,-y,x pigment{rgb 1}double_illuminate translate Offset*z
	finish{reflection 1} no_image no_shadow no_reflection}
polygon{5,x,y,-x,-y,x pigment{rgb 1}double_illuminate translate -Offset*z
	finish{reflection 1} no_image no_shadow no_reflection}

This is you original scene with the following changes:
Added no_shadow on the original polygons.
Added 2 reflective polygons just outside the original ones, with no_everything. 
That way, they reflect but don't show, don't have shadow and don't reflect on 
each other.
Increased count, less that 1000 and you get artefacts.
Had also to reduce error_bound.

-- 
Alain
-------------------------------------------------
Bend the facts to fit the conclusion. It's easier that way.

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