Stephen <mca### [at] aolcom> wrote:

>
> Another way of saying what Alain said in non technical terms.
>
> When you set the location of the spotlight (you set it to < 0,0,0 >)
> then set the point_at. PovRay will calculate the angles. If you then
> transpose the spotlight the point_at will still keep these angles and
> the light beam will miss your sphere.
>
> An alternative method would be to take the spotlight coordinates from
> your Blender light and use them as the location in the PovRay Spotlight.
> Then the point_at will work as you want it to if you do not add any more
> translations or rotations.
> Be aware if you do this then the centre of rotation of the spotlight
> will be at the origin.
>

> Regards
>      Stephen

Stephen, Alain, thank you very much!


LanuHum

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Alain <kua### [at] videotronca> wrote:

>
> #declare Middle=0;
> //ground plane
> plane{y,0 pigment{rgb 1/8}}
>
> //a back plane to keep rays finite
> plane{-z,-30 pigment{rgb 0}}
> //the camera
> camera{location<0,10,-30> look_at 0}
> // setting the creation of 5 lights in a loop
> #declare L_Num=5;
> #while(L_Num>0)
> light_source{<-25,90,0> rgb 8
> spot_light radius 1 falloff 2
> #if(Middle=1)translate 10*x #end
> // this translate ONLY the light and NOT the point_at
>
> point_at 0
>
> #if(Middle=0)translate 10*x #end
> // This translate BOTH the light and the point_at
>
> #declare L_Num=L_Num-1;
> #end // of the loop
> media{scattering{1 rgb 0.1}}///////ERROR!!!!!!!
>

> Alain

media{scattering{1 rgb 0.1}}///////ERROR!!!!!!! Scattering in light source??????

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> Alain <kua### [at] videotronca> wrote:
>
>>
>> #declare Middle=0;
>> //ground plane
>> plane{y,0 pigment{rgb 1/8}}
>>
>> //a back plane to keep rays finite
>> plane{-z,-30 pigment{rgb 0}}
>> //the camera
>> camera{location<0,10,-30> look_at 0}
>> // setting the creation of 5 lights in a loop
>> #declare L_Num=5;
>> #while(L_Num>0)
>> light_source{<-25,90,0> rgb 8
>> spot_light radius 1 falloff 2
>> #if(Middle=1)translate 10*x #end
>> // this translate ONLY the light and NOT the point_at
>>
>> point_at 0
>>
>> #if(Middle=0)translate 10*x #end
>> // This translate BOTH the light and the point_at
>>
>> #declare L_Num=L_Num-1;
>> #end // of the loop
>> media{scattering{1 rgb 0.1}}///////ERROR!!!!!!!
>>
>
>> Alain
>
> media{scattering{1 rgb 0.1}}///////ERROR!!!!!!! Scattering in light source??????
>
>
>

In the sample scene I made, I forgot to close the light_source block.
Put the missing closing brace "}" between "#if(Middle=0)translate 10*x 
#end " and "#declare L_Num=L_Num-1;".

The media should be defined by itself or in a transparent object with 
the "hollow" option.
The purpose of "hollow" is strictly to enable an object to contain some 
media and to allow fog to exist within.

The media is proposed to make the light beams visible.

This is a minimal athmospheric scattering media block placed by itself 
outside of any object or scene element:

media{scattering{1 rgb 0.1 } }

This create an isotropic scattering media filling your entire scene.


Sample media box with the same media (usualy prefered):

box{<-50,0,0><50,100,100> pigment{rgbt 1} hollow
interior{media{scattering{1 rgb 0.1}} }
}

This create a minimal scattering media within the box. This usualy 
renders faster.

By minimal, I mean using all default parameters and without any density 
variation.



Alain

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